Download Cell biologgy Q&A2

CELL BIOLOGY
QUESTIONS AND ANSWERS
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1) CARBOHYDRATE
a) Monosaccharides & Disaccharide
b) Polysaccharides & identification tests
c) Identification tests of Carbohydrates
2) PROTIENS
3) LIPIDS
4) NUCLEIC ACID
5) WATER
6) VITAMINS AND MINERALS
a) Vitamins
b) Mineral
7) PROCARYOTES AND EUCARYOTES
8) VIRUS
9) CELL BOUNDARIES
a) Cell wall
b) Plasma membrane
10) ORGANS OF THE CELL
a) Cell nucleus
b) Endoplasmic reticulum
c) Golgi apparatus
d) Lysosomes
e) Peroxisome
f) Vacuole
g) Mitochondria
h) Ribosome
i) Functions of organelles
11) CELL CYCLE & CELL DIVISION
12) PHOTOSYNTHESIS
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1. CARBOHYDRATES
i) [Monosaccharides & Disaccharide]
1.Briefly describe what is carbohydrates.
Carbohydrate is an organic compound which contain C, H, O. The formular of carbohydrate is
Cx (H2 O) y. There are three major groups. They are monosaccharides, disaccharides and
polysaccharides.
2. Briefly describe monosaccharide.
Monosaccharide is the simplest form of carbohydrates. All monosaccharide is reducing sugars,
water soluble and occur in crystalline form. There are various monosaccharides in C 3-7.
•
•
•
•
3C- Triose - Glyceraldehyde
4C- Tetroses - Erythrose
5C- Pentoses - Ribose, Deoxyribose, Ribulose
6C- Hexoses -Glucose, Fructose, Galactose
3. Describe what is disaccharide.
A disaccharide is formed by the binding of 2 monosaccharide molecules by glycosidic bond.
Maltose and lactose are reducing sugars and sucrose is a non-reducing sugar. Here, a water
molecule is removed.
Glucose + Glucose
Maltose + H2 O
Glucose + fructose
Sucrose + H2 O
Glucose + Galactose
Lactose + H2 O
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4. Describe what are reducing sugar and non-reducing sugar.
•
•
The sugar that donates electrons is called reducing sugar. All monosaccharides and
disaccharides (without sucrose) are reducing sugar.
The sugar that cannot donate electrons is called non-reducing sugar. All the
polysaccharides and sucrose are non-reducing sugar.
5. Describe what is the reason for divide as aldose and ketose.
The reason for divide as an aldose and ketose is to the type of carbonyl group. The example for
Aldose is glucose and galactose and the example for ketose is sucrose.
6. What are the functions of Monosaccharides and Disaccharides.
Monosaccharides
•
•
•
As an energy source
As a building blocks of disaccharides and polysaccharides
As a components of nucleotides
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Disaccharides
•
•
As a storage sugar in milk- Lactose
As a means of transporting energy- Sucrose
7. All these compounds are carbohydrates.
A- This is a primary carbohydrate our bodies use to produce energy. Main product of
photosynthesis.
B- This is the storage sugar in milk. This is a disaccharide and formed by A+Galactose.
C- Foods in phloem travel as this substance. This is a disaccharide and formed by A+Fructose.
D- This is a disaccharide formed by the combination of two A molecules.
What is A, B, C, D molecules?
A- Glucose
B- Lactose
C- Sucrose
D- Maltose
8. Carbohydrates are the most abundant organic compound on Earth. Describe how is this
happens.
Cellulose is most abundant substance in earth because cellulose can be found in all most all
living plant cell wall. Cellulose is a carbohydrate. Therefore, Carbohydrates are the most
abundant organic compound on Earth.
9. ‘Cows can digest cellulose whereas human cannot’. Briefly explain this statement.
Humans are unable to digest cellulose because the appropriate enzymes are not in humans’ body.
But cow's body has cellulose digest enzyme. Therefore, they can digest cellulose.
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ii)[Polysaccharides & identification tests]
1.
Briefly explain what are the polysaccharides of carbohydrates?
Polysaccharides are the most abundant carbohydrate found in food. They are long chain
polymeric carbohydrate composed of monosaccharide units bound together by glycosidic
linkages.
2.
All carbohydrate is polymers. briefly explain whether you agree with this statement.
Not agree
Monosaccharide and disaccharides are monomers. But all polysaccharides are polymers. They
are long chain polymeric carbohydrate composed of monosaccharide units bound together by
glycosidic linkages.
3.
Carbohydrates are linked to each other by glycosidic bonds, because every
carbohydrate has the glycosidic bonds. Briefly explain whether you agree with this
statement.
Not agree
Monosaccharaides are simple sugar. Because all monosaccharide has not glycosidic bonds.
But all disaccharides and polysaccharides linkage to each other glycosidic bonds.
-
Extra knowledge.
Monosaccharide
disaccharides
H2O
Polysaccharides
H2O
H2O
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4.
What are the examples of homo polysaccharides? briefly explain one of these examples.
➢ Starch
➢ Glycogen
➢ Cellulose
Starch - Starch is a soft, white, tasteless powder that is insoluble in cold water, alcohol, or
other solvents. Starch is a polysaccharide comprising glucose monomers joined in α 1-4
linkages and α 1-6 linkages . The simplest form of starch is the linear polymer amylose;
amylopectin is the branched form.
Extra knowledge
C6
CH2OH
0
1-4
α Glycosidic
C5
C1
C4
C3
C2
Glycogen - Glycogen is a multibranched polysaccharide of glucose that serves as a form of
energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the
main storage form of glucose in the body. In humans, glycogen is made and stored primarily
in the cells of the liver and skeletal muscle. Glucose monomers joined in α 1, 4 linkages and
1-6 linkages.
α
Glycosidic
1-6
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1-4 and 1-6 α, Glycosidic
Cellulose- Cellulose is the main substance in the walls of plant cells, helping plants to remain
stiff and upright. Humans cannot digest cellulose, but it is important in the diet as fiber.
5. Briefly explain heteropolysaccharides.
Heteropolysaccharides is a polysaccharide. We can divide in to path. glycosaminoglycans and
mucilages. Example of Heteropolysaccharides is hyaluronic acid and heparin. Hyaluronic acid
we can find the most concentrated sources of hyaluronic acid in the skin, connective tissues. And
heparin is usually stored within the secretory granules of mast cells. And examples of mucilages
are agar, pectin, and hemicellulose.
6. Briefly explain the importance of pectin.
Pectin, any of a group of water – soluble carbohydrate substances that are found in the cell
walls and intercellular tissues of certain plants.in the fruits of plants, pectin helps keep the walls
of adjacent cell joined together .as a result, the overripe fruit becomes soft and begins to lose its
shape.
7. Briefly explain structural polysaccharides of chitin.
Chitin is a polysaccharide forming the exoskeletons of many invertebrates.it is a polymer of Nacetylglucosamine in beta 1 to 4 glycosidic linkage.
8. Write correct answer.
➢ What is the polymer of with 1-4 α glycosidic bonds? – starch
➢ What is the polymer of with only 1-4 α and 1-6 α glycosidic bonds? - Glycogen.
➢ Which polymer is we can find 1-4 beta glycosidic bonds? Cellulose
Extra knowledge
OH
OH
α- GLUCOSE
β- GLUCOSE
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9. What are the functions of polysaccharide?
•
•
•
As a structural material.
Energy source.
Components of several metabolic pathways.
10. Role of carbohydrate.
•
•
•
•
As a major energy source for living organisms.
As a means of transporting energy.
As a structural material.
As a precursor for other biochemical.
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iii)Identification tests of Carbohydrates
11. Briefly explain how we can identify monosaccharide in Fehling test.
Fehling solution= Fehling A [CUPRIC SULFATE] and Fehling B [Rochelle salt/
potassium sodium tartrate tetra hydrate.]
Here the aldehydes reduce the complexes copper (ll) ion to copper (l) oxide and
the aldehyde itself is oxidized to a salt of the corresponding carboxylic acid under
alkaline conditions.
A positive test – green suspension and a red precipitate upon of the Fehling
solution with the test sample.
✓ ALL Reducing Sugars ANSWER THE FEHLING
TEST.
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12. Briefly explain how we can identify monosaccharide in benedict test.
It reacts chemically like Fehling solution the cupric ion (complexed with citrate) is
reduced to cuprous ion by the aldehyde group (which is oxidized) and precipitates
as cuprous oxide.
Positive result-
A brick- red precipitate and a change in color, often blue to red depending upon the
amount of reducing sugar present test sample.
✓ ONLY Reducing Sugars ANSWER THE
FEHLING TEST.
13.Reaction between starch and iodine solution
When iodine solution is added to a suspension of starch, the iodine molecules pack
inside the amylose to give
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2. PROTIENS
1.What is a protein?
•
A large biomolecules & macromolecules that comprise one or more long chains of amino
acid residues.
2.What is the monomer of proteins?
•
Amino acids
3.Draw the general structure of amino acid.
4.Describe the meaning of characteristic of amphoteric in amino acids.
•
In amino acids there are both acid and base parts. It contains a carboxylic group, so it act
as an acid. Also contains an amino group. It act as a base.
5.What is the meaning of Chiral C of a amino acid
•
Both amino group & carboxylic group have connected to the same c atom in the amino
acids. So this c atom called as “Chiral C”.
6.Which one defines an amino acid according to the structure of it?
•
R group (The variability of R group decide the physical & chemical characteristic of
amino acids)
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7.How simplest amino acid is formed?
•
In amino acid there is a R group. So when H(Hydrogen) consists as the R group, simplest
amino acid creates.(Glycine)
8.What are the examples for the R group consists of S(Sulfur)
•
•
Cysteine
Methionine
9.How proteins are formed?
•
When same or different amino acids are combined together with each other through
peptide bonds.
10.Why proteins are called as heterogeneous polymer?
•
•
None of polypeptides are consist of same type of amino acids. According to the number
of amino acids, types of amino acids, order of amino acids, a polypeptide is difference
with another polypeptide.
[The amino acids which make the proteins are not consisted of P(Phosphorus)]
11.What are the naturally occurring amino acids?
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12.How peptide bond is formed?
•
The COOH group of one amino acid binds to the NH2 group of another amino acid.
Between them peptide bond is formed.
13.Briefly explain following mention things
•
•
•
Dipeptide=When two amino acids bind together through the peptide bond
Tripeptide=When three amino acid bind together through the peptide bond
Polypeptide=When more amino acids bind through the peptide bond
14.In what way polypeptides are in protiens.
•
There are one or more polypeptide chains folded into highly specific 3D shape
15.What are the four levels of protein structure?
•
•
•
•
Primary
Secondary
Tertiary
Quaternary
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16.Briefly explain the each one level of protein structure & process.
Protein structure
• Primary
•
Secondary
•
Tertiary
•
Quaternary
Definition
Process
• Sequence of amino
• Assembly
acids
• Forms pleated
• Folding
sheet,helix or
coil(Basic structure of
polypeptide chain)
• Entire length of amino
• Packing
acids folded into a
shape
• Several amino acids
• Interaction
sequences linked
together
17.What is the special bond which in the tertiary structure?
•
Disulphide Bond
18.What is the example of quaternary structure?
•
Ferritin (The bodies iron storage protein)
19.What are the several bonds in 3D shape of a protein.
•
•
•
Hydrogen Bonds=Involved in all levels of structure
Hydrophobic Interactions=Between non-polar sections
Disulfide Bonds=One of the strongest bond & most important type of bond in proteins.
20.How can classify the amino acids?
Amino acids with,
•
•
•
•
•
•
Non polar aliphatic side chains
Aromatic side chains
Side chains containing hydroxyl group
Side chains containing sulfur atom
Acidic side chains
Basic side chains
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21.How can classify the proteins?(Based on the physiochemical properties of proteins)
•
•
•
Simple proteins
Compound proteins
Derived proteins
22.What are the simple proteins?
•
The proteins which are made of amino acid units only joined by peptide bond.
23.What are the examples for simple proteins?
•
•
•
•
Albumins
Globulins
Histones
Albuminoids (Collagen, Elastin, Keratin)
24.What are the Compound/Conjugated proteins.
•
The proteins which composed of simple proteins combined with non-proteinous
substance.
25.What is called as “Prosthetic group or Cofactor?
•
In compound protein, they composed of simple proteins with non-proteinous substance,
So, that non-proteinous substance is called as prosthetic group(Cofactor).
26.What are the examples for conjugated proteins?
•
•
•
•
•
•
Nucleoproteins(Histone+DNA,RNA)
Phosphoproteins(Casein of milk,Vitellin of egg)
Lipoproteins
Proteo/Glycoproteins
Chromoproteins(Hemoglobin,Rhodopsin,Cytochromes)
Metalloproteins(Ferritin-Fe,Carbonic anhydraze-Zn)
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27.What are the derived proteins
•
These are not naturally occurring proteins & obtained from simple proteins by the action
of enzymes & chemical agents.
28.What are the two types of derived proteins?
•
•
Primary derived
Secondary derived
29.How can classify the proteins according to the functions?
•
•
•
•
•
Catalytic protein (enzymes)
Transport protein (Transferrin,Ceruloplasmin)
Structural proteins(Actine,Myosin)
Genetic proteins(Histones)
Storage proteins(Casein,Gluten)
30.What is the meaning of Axial ratio?
•
Molecular length/Molecular width
31.How can classify the proteins according to the molecular length & shape?(Depend on
the axial ratio)
•
•
Fibrous=Axial ratio more than 10
Globular=Axial ratio less than 10
32.What are the functions of proteins?
•
•
•
•
•
•
•
Enzyme catalysts=Specific for one reaction
Defense=Antibody proteins,other proteins
Transport=Hgb,Mgb,trnasferrins
Support=keratin,fibrin,collagen
Motion=actin/myosin,cytoskeletal fibers
Regulation=Some hormones, regulatory proteins on DNA,cell receptors
Storage=Ca & Fe attached to storage proteins
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i)PROTEIN IDENTIFICATION
1.For what biuret test is proceed?
•
To show the presence of peptide bonds, which are the basis formation of proteins.
2.What happen if there are peptide bonds in substances which we take to test?
•
The bonds will make the blue biuret reagent turn purple/violet
3.What are the reagents that we use in biuret test
•
•
Potassium hydroxide(KOH)/Sodium hydroxide(NaOH)
1% copper sulfate(CuSO4)
4.What are the steps for biuret test
•
•
•
•
•
Equal amount of NaOH is added to a solution of the protein solution.
Mix it carefully.
Then few drops of 1% CuSO4 is added.
But do not shake the mixture.
Purple/violet colour is a positive result(protein is present).
5.For what NAOH use in biuret test?
•
To raise the pH of the solution to alkaline levels.
6.What happen when there are peptide bonds?
•
When peptide bonds are present in the alkaline solution, the cu2+ ions will form a
coordination complex with 4 nitrogen atoms from peptide bonds.It makes colour of cuso4
solution,chnges from blue to violet.
7.On what the colour changes of solution depend?
•
Number of peptide bonds in the solution.(More protein more intense the change)
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3. Lipids
1. What are the main types of lipids?
There are two types of lipids called simple and compound lipids. Triglycerides (fats and oils) is an example
for simple lipids. Phospholipids, waxes(cutin) and steroids(cholesterol) are example for compound lipids
which
same
as
simple,
but
with
other
compounds
also
attached.
2. What is the molecular structure of glycerol? To which organic functional group does this
substance belong?
Glycerol is a three carbon atom structure. The central carbon atom is bound to one hydroxyl radical and to
one hydrogen atom and the two other carbon atoms at the ends are bound to a hydroxyl radical and to two
hydrogen atoms. Spatial position side of the hydroxyl radicals is the same.
3. What is the composition of triglycerides?
Triglycerides are fats or oils, which made from three molecules of fatty acids bound to one molecule of
glycerol. Hydroxyls of each one of the three fatty acids and each hydrogen atom of the hydroxyls of the
glycerol bind together with ester linkage and release three molecules of water.
Ester linkage
H
|
H – C – OH
|
H – C – OH
|
H – C – OH
|
H
Glycerol
+
O
||
HO – C – R1
O
||
HO – C – R2
O
||
HO – C – R3
3 Fatty acids
-3H2O
H
O
|
||
H – C – O – C – R1
O
||
H – C – O – C – R2
O
||
H– C – O – C – R3
|
H
Triglyceride
4. What are phospholipids?
Phospholipids are molecules made up of one molecule of glycerol bound to two long molecules of fatty
acids and to one phosphate group. Therefore, phospholipids are amphipathic molecules, meaning that they
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have a non-polar portion, due to the long fatty acid chains, and a polar portion, due to the phosphate group.
As a result, it forms a hydrophobic head and two hydrophilic tails Phospholipids are the main component
of cell membranes.
5. What are steroids? What are some examples of steroids with a biological function?
Steroids are lipids that consist of an angular combination of four carbon rings. The bond between each ring
and the adjacent ring is made through by the sharing of two adjacent carbon atoms which belong to both
rings. Bile salts, cholesterol, the sexual hormones estrogen, progesterone and testosterone, corticosteroids
and pro-vitamin D are examples of steroids.
6. What are hydrophobic molecules (or hydrophobic molecular regions)? What are hydrophilic
molecules? How can they be described in relation to their polarity?
Hydrophobic molecules are molecules with little or no propensity to dissolve in water. Hydrophilic
molecules are those that have a large propensity to dissolve in water.
Water is a polar substance. Hydrophobic substances are non-polar molecules whereas hydrophilic
molecules are polar molecules.
7. Explain the structure of phospholipids in cell membrane
Phospholipid in cell membrane are amphipathic molecules. Fatty acid chains are hydrophobic. So, they are
non-polar and insoluble in water. Lipids in general are molecules with a large non-polar extension, making
them soluble in non-polar solvents. Phosphate group & Glycerol forms a hydrophilic head which are polar
and soluble in water. So, when phospholipid is added to the water, they self-assemble into bi layer with
hydrophobic tails pointing towards the interior and forms a bi layer. That is the reason the structure of
phospholipids in cell membrane results a bi layer.
8. What is meant by saturation or saturated fats?
Saturated fats have maximum number of H atoms and all bonds are single. Hydrocarbon chains are fairly
straight and can pack closely together. They are solid at room temperature. Example of saturated fats are
butyric acid in butter and lauric acid in coconut oil. Food high in saturated fats raise blood cholesterol.
•
•
Primarily animal sources: meat, poultry, milk, butter, cheese, egg yolk, lard
Plant Sources: chocolate, coconut, coconut oil, palm oil
▪
Saturated Fat increases total cholesterol and increases LDL-cholesterol
9. What is meant by unsaturation or unsaturated fats?
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Unsaturated fats are made of fatty acids that have double bonds between C atoms in the tail. That bonds
cause bends in the shape of the molecule and can’t pack close together which making them liquid at room
temperature. They are spontaneously oxidizing with molecular O2 at their double bonds.
There are two types of unsaturated fats called monounsaturated which contains one double bond and
polyunsaturated which contain two or more double bonds. α-Linoleic acid (omega 3), Linoleic acid (omega
6) are examples of polyunsaturated fatty acid.
• monounsaturated fats- EX- avocado, peanuts, olive oil (oleic acid), Canola, many nuts and seeds.
•polyunsaturated fatty acid -EX- soybean, sunflower, canola, margarine, mayonnaise, certain nuts, fish.
•
Polyunsaturated fat decreases total cholesterol & LDL-cholesterol & Decreases HDL-cholesterol
10. Why do fats have thermal insulation properties?
Triglycerides are poor heat conductors. They form thick layers of fatty tissue when accumulated in an
organism. That is why they are good thermal insulators. In animals that live in cold climates, such as polar
bears, seals and whales have adipose tissues that help to maintain the internal body temperature.
11. How are lipids used as an energy source by the body?
Carbohydrates are the main energy source for cell respiration. When such substances are absent or deficient,
the body can use lipid stores since fats can be broken down into acetyl-CoA to feed the Krebs cycle which
is a stage of cellular respiration.
12.What are the industrial uses of fats and oils?
•Fats and oils are used as food like margarine, food emulsifiers, cooking oils, ice cream.
•Fats and oils are used in medicinal industry for ω -3 fatty acids, Vitamin A and D supplement.
•Fats and oils are used in chemical industry for soap, detergent, paint.
13.what are the good things/advantages about fats?
Fats are very important for good health and proper function of the body. They are source of energy and
stores energy in fat cells for long term use. They act as flavour carrier and heat transfer. They help to
improve texture and mouthfeel. Some fats are essential fatty acids like linoleic & linolenic which need for
body.
They
carry
fat
soluble
vitamins
such
as
vitamin
A,
D,
K,
E.
14.what are the bad things/disadvantages about fats?
As we know we need fats for proper functioning of body. But too much fat or unnecessary fats taking may
affect negatively to our health. They may cause diseases like heart disease, high blood pressure, cancer.
Unsaturated fats are reactive free radical.
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15.What are trans fats?
Trans fats are unsaturated fats that have low energy configurations where the two largest substituents are
on opposite sides of the double bond. A trans bond is a straight bond.
16.What are cis fats?
Cis fats are unsaturated fats. So, they have double bond with the two largest substituents on the same side
of the double bond.
17.What is the difference of trans and cis fats?
Unsaturated fats are in cis and trans forms according to the arrangement of the carbon chains. So, they both
have double bonds. A cis bond forms with the two largest substituents on the same side of the double bond.
Trans bonds are low energy configurations where the two largest substituents are on opposite sides of the
double bond. A trans bond is a straight chain while cis has a bent on the chain.
18.Why trans-fat known as a hidden killer? Bad side of the trans-fat?
Trans-fat increases total cholesterol and LDL-cholesterol. Actually, it’s a fat that’s difficult to digest so it
increases the amount of bad cholesterol in your blood and can dramatically boost your risk of heart disease.
They don’t raise the level of good or HDL cholesterol. If saturated animal fats are unhealthy, trans fats are
far
worse.
19.What are cholesterols?
•
•
•
Cholesterol is a sterol that has a rigid ring system and a short-branched hydrocarbon tail.
It is an important solid component of cell membrane in animal cell and is naturally produced by
the body.
About 80% of the body's cholesterol is produced by the liver, while the rest comes from our diet.
Types of Cholesterol
20.What are LDL Cholesterol?
LDL cholesterol means low density lipoprotein which known as "bad" cholesterol. They carry cholesterol
around in the blood. They elevated levels of LDL cholesterol are associated with an increased risk of
coronary heart disease.
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LDL lipoprotein deposits cholesterol on the artery walls, causing the formation of cholesterol plaque and
over time, cholesterol plaque causes narrowing of the arteries.
21.What are HDL Cholesterol?
HDL Cholesterol means high density lipoprotein which known as “good cholesterol”. Because HDL
cholesterol particles prevent narrowing of the arteries by extracting cholesterol from the artery walls and
disposing of them through the liver.
High levels of LDL cholesterol and low levels of HDL cholesterol (high LDL/HDL ratios) are risk factors,
while low levels of LDL cholesterol and high level of HDL cholesterol (low LDL/HDL ratios) are desirable.
21.What are VLDL Cholesterol?
VLDL cholesterol means very low-density lipoprotein cholesterol is produced in the liver and released into
the bloodstream to supply body tissues with a type of fat (triglycerides). High levels of VLDL cholesterol
have been associated with the development of plaque deposits on artery walls, which narrow the passage
and restrict blood flow.
Total cholesterol is the sum of LDL (low density) cholesterol, HDL (high density) cholesterol, VLDL (very
low density) cholesterol (triglycerides) cholesterol.
22.What are the normal cholesterol levels in our blood?
•Total Cholesterol < 200 mg/dL
• LDL 0-130 mg/dL
• HDL 33-96 mg/dL
• Triglycerides 40-157 mg/dL
23.How we can manage our body fat?
We should eat a healthy diet while exercising regularly. We should try to keep our weight in normal range.
If we have hypertensive or diabetic, we should keep it under control. We shouldn’t smoke tobacco. We
have to get your cholesterol checked at least once a year if you have risk factors.
24. How Saturated Fat affect cholesterol?
They increase total cholesterol and LDL-cholesterol.
25. How Polyunsaturated Fat affect cholesterol?
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They decrease total cholesterol and LDL-cholesterol and HDL-cholesterol.
26. How Monounsaturated Fat affect cholesterol?
They decrease total cholesterol and LDL-cholesterol and Increase HDL-cholesterol.
27. How Omega-3 Fat affect cholesterol?
They decrease total cholesterol, LDL-cholesterol, serum triglycerides and increases HDL-cholesterol.
28. How trans Fat affect cholesterol?
Trans Fat increase total cholesterol and LDL-cholesterol.
29. What is the identification test for fat?
Sudan III test is used as fat identification. Sudan III is a red fat-soluble dye that is utilized in the
identification of the presence of lipids, triglycerides and lipoproteins. First, we have to take a test tube and
add equal parts of test liquid &water to fill about half full. Then 3 drops of Sudan III stain should be added
to each test tube. Then it should be shake gently to mix. A reddish orange-stained oil layer will separate out
and float on the water surface if fat is present.
30. Briefly explain why doctors recommend not to use oil for deep frying food items many times.
Fried Foods Are Typically High in Trans Fats. Trans fats are formed when unsaturated fats undergo a
process called hydrogenation. But hydrogenation also occurs when oils are heated to very high temperatures
during cooking. The process changes the chemical structure of fats, making them difficult for your body to
break down, which can ultimately lead to negative health effects. In fact, trans fats are associated with an
increased risk of many diseases, including heart disease, cancer, diabetes and obesity
4. Nucleic Acid
1. What are the two types of Nucleic Acids?
Deoxyribonucleic Acid (DNA)
Ribonucleic Acid (RNA)
2. What is Deoxyribonucleic Acid (DNA)?
It is the hereditary material in humans and almost all other organisms.
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3. Where is DNA and RNA can find in prokaryotic cell?
DNA – in the nucleic region.
RNA – in the nucleic region and Ribosomes.
4. Where is DNA and RNA can find in eukaryotic cell?
DNA – in the nucleus; with small amount in mitochondria and chloroplast.
RNA – throughout the cell.
5. What are the Nucleotides?
Sub units of DNA and RNA.
6. What are the linkages in phosphate groups and nucleotides, we can find in DNA and
RNA?
Phosphodiester bonds
7. What are the functions of Nucleotides?
•
•
•
Building block for DNA and RNA.
Intracellular source of energy. – Adenosine triphosphate (ATP)
Intracellular signaling switches. (e.g.: G-proteins)
8. What are the differences of DNA and RNA?
DNA is a double-stranded molecule, while RNA is a single-stranded molecule. DNA is
stable under alkaline conditions, while RNA is not stable. DNA has deoxyribose sugar
molecules and RNA has ribose sugar molecules. DNA and RNA base pairing is slightly
different since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses
adenine, uracil, cytosine, and guanine.
9. What is Nucleoside?
Nitrogen bases and sugar molecule structure. It hasn’t phosphate group.
10. Explain how is a phosphodiester bond formed between a group of phosphate and a
group of sugar?
The phosphate group joins the 3rd carbon of one sugar to the 5th carbon of the next line.
So, this is the way of phosphodiester bond form.
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11. What is the name of DNA structure model?
Double helix model / Watson and Crick model
12. Explain the “Double helix model”.
It has antiparallel two backbones. Its base pairing in complementary. Each base is paired
with a specific partner. Adenine is always paired with Thymine. Guanine is always paired
with Cytosine. The bases are joined by hydrogen bond, individually weak by collectively
strong.
13. What are the three types of RNA and describe their functions.
m-RNA (messenger RNA) – Transmits information from DNA and serves as a template
for protein synthesis.
t-RNA (transfer RNA) – Brings amino acids to ribosomes for protein synthesis.
r-RNA (ribosomal RNA) – Ribosomal RNA and proteins make up ribosomes.
14. How are the nitrogen bases connected to the backbone and how are they connected to
each other?
DNA has a double-helix structure, with sugar and phosphate on the outside of the helix,
forming the sugar-phosphate backbone of the DNA. The nitrogenous bases are stacked in
the interior in pairs, like the steps of a staircase; the pairs are bound to each other by
hydrogen bonds.
15. What is meant by complementary base pairing?
The standard arrangement of bases in nucleotides in relation to their opposite pairing,
such as thymine being paired with adenine and cytosine paired with guanine.
16. What is meant by DNA replication?
DNA replication is the process by which a double-stranded DNA molecule is copied to
produce two identical DNA molecules. Once the DNA in a cell is replicated, the cell can
divide into two cells, each of which has an identical copy of the original DNA.
17. What basically occurs in DNA replication?
The result of DNA replication is two DNA molecules consisting of one new and one old
chain of nucleotides. This is why DNA replication is described as semi-conservative, half of
the chain is part of the original DNA molecule, half is brand new.
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5. Water
1. Explain why there is only a small fraction of the total amount of water we can use?
About 71 percent of the Earth's surface is covered by water but about 97.5 percent of that
water is exists as salt water. About 2.5 percent of the world's water is exists as freshwater.
However, only 0.77 percent of water exists as accessible fresh water. This is because
freshwater also exists as polar ice caps and glaciers. For these reasons, the amount of water
that can be used is very small out of the total amount of water.
2. Explain what does water do for you?
Water is a vital inorganic molecule and life could not exist on this planet without water.
Water does a lot of things to sustain our life. Water is the major component of most body
parts. Furthermore, in saliva that comes out of the mouth mainly contains water and which
helps in digestion (Converts food to components needed for survival). Water allows body’s
cells to grow, reproduce and survive. Water needed by the brain to manufacture hormones
and neurotransmitters. Water is also important where the body excretes wastes, mainly
through urine. It is also important as a lubricant for joints. Water also helps to keep the
mucous membranes moist and water helps deliver oxygen all over the body. Furthermore,
Water regulates body temperature by sweating and respiration.
3. Explain why water is important us?
Water is important as a solvent, reactant, product, heat transfer medium, texture,
preservation, and terms of the economy. Water is a good solvent and most substances are
dissolved in water. Water is a reactant in many reactions and involve in hydrolysis reactions,
and water is acts as a product in condensation reactions. Due to the high specific heat
capacity of water, water acts as a heat transfer medium. Water helps to build the texture of
vegetables, fruits and many foods. Its juiciness and mouthfeel are found in the snack foods,
vegetables and meat. Most of the food preservation method are interact with water and most
perishable foods are preserved by removing water. Nowadays pure water has a high value
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and adding and removing water to food can add more value to food therefore, it is also
important economically.
4. Explain what are the main properties of water?
Most of the molecule dissolved in water therefore it is called Universal Solvent. Pure water
has a high transparency and water has three physical phases liquid, solid and vapor. Due
to the special composition of the water, highest density of water is at 4 degrees Celsius.
water has high specific heat Its means water can tolerate high amount of heat. Water has a
high heat of vaporization, so it absorbs a large amount of heat as it evaporates. Water has a
very low compressive capacity. Another special property of water is the Stickiness between
water Molecules.
5. Explain Why water has unique properties?
Water has unique structure. Water molecules are polar that means that there is an uneven
distribution of electron density, so they form hydrogen bonds. These hydrogen bonds play a
major role in maintaining all the properties of water. This gives water unique properties, such
as a relatively high boiling point, high specific heat, specific heat, universal solvent capillary
action, cohesion, adhesion and density.
6. Explain the structure of water?
Water molecule is a small, polar and angular molecule consisting of one oxygen atom
bonded to two different hydrogen atoms. Those atoms are connected by tow covalent bond of
104.5 degrees.
7. Explain how water is considered as a polar substance?
Polarity is an uneven electron distribution within a molecule. In water molecule, oxygen
atom is slightly negative and hydrogen atom is slightly positive.
8. Explain the term "capillary action"?
Capillary action is the process of a liquid flowing in narrow spaces due to the combined force
of attraction among water molecules and with the molecules of the surrounding material.
Cohesion and adhesion bonds of water cause a small space of water to move upward against
gravity. This helps move water to the tops of tall trees and through veins in humans.
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9. Briefly explain, what is the surface tension of water.
Hydrogen bonds due to the polarity of water, on the surface of the water an “elastic
membrane” forms. Because of this makes the surface act a solid. This provides habitat for
some aquatic insects. / The property of the surface of a liquid that allows it to resist an
external force, due to the cohesive nature of its molecules
10. Explain how surface tension of water can be important in life.
Small insects such as the water strider can walk on
water because their weight is not enough to
penetrate the surface. Water striders are able to
walk on top of water due to a combination of
several factors. Water striders use the high surface
tension of water and long, hydrophobic legs to help
them stay above water.
11. Why is water called a universal solvent?
Most substances (Lot of things) can be dissolved in water. Other polar molecules can be
dissolved by water.
12. Explain what are the cohesion and adhesion.
Cohesion is the attractive force between water molecules. Because water is polar molecules,
it is attracted to itself. (This is important to keep the acacia plants straight)
Adhesion occurs when molecules of water are attracted to other substance. Because water is
a polar molecule, it is attracted to other substances.(This is important to the absorption of
water and minerals from the solid solution)
13. Why is water’s density important for life.
Unlike most substances, water becomes less than dense when it freezes. Greatest density of
water at 4 degree of Celsius. Due to this, the water in the reservoirs does not completely free
in water. Liquid water is present at the bottom of reservoirs. Ice is on the surface of that
water. This allows the fish to survive the water.
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14. What is the reason for different life found at bottom of ocean compared to top?
Cold water is denser than hot water. Because of this, the cool water is at the bottom of the
ocean and the surface is hot water.
15. Explain the specific heat of water.
Specific heat mean the amount of energy needed to increase the temperature of something
one degree Celsius. What takes a lot of energy for increase its temperature. Reason for this
strong attraction between water molecules.
16. What are the importance in specific heat of water for life?
Prevent from overheating. Evaporation of sweat from human skin helps to maintain the body
temperature at Constant level. Transpiration in plants keeps the plant body surface as a cool
surface and prevent from Becoming too warm in the sunlight.
6. Vitamins and minerals
i) Vitamins
1. What is the difference between water-soluble and fat-soluble vitamins? Why can fatsoluble vitamins cause harm when ingested in excess?
Water-soluble vitamins are those which are soluble in water. Fat-soluble vitamins are those
which soluble in oil (lipids, fat). Vitamin C and the vitamins of the B complex are examples
of water-soluble vitamins. Vitamins A, D, E and K are examples of fat-soluble vitamins.
Fat-soluble vitamins, since they are not soluble in water, cannot easily be excreted by the
body. As a result, they tend to accumulate in tissues, producing a toxic effect when they are
ingested in amounts beyond what is necessary
2. What is the main damage caused by vitamin A deficiency? What is the role of this
vitamin in the physiology of vision?
Vitamin A (retinol) deficiency may cause night blindness, corneal dryness (xerophthalmia)
and predisposition to skin injuries.
In the physiology of vision, vitamin A participates in the formation of rhodopsin, a pigment
responsible for the ability to see in places with less light.
3. What is folic acid? Why is the anemia caused by the deficiency of folic acid known as
megaloblastic anemia?
Folic acid (when ionized it is called folate) is a coenzyme that participates in the synthesis
and duplication of DNA and, for this reason, it is necessary for cell division. If there is not
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enough folic acid in cells with a high turnover rate, such as red blood cells, their production
will be reduced.
n folic acid deficiency, precursor cells (reticulocytes) that would produce erythrocytes (red
blood cells) begin cell division but the process is very slow whereas cytoplasm growth is
normal. As a result, cells become abnormally large, which is the typical feature of
megaloblastic anemia
Megaloblastic anemia can also be caused by vitamin B12 (cyanocobalamin) deficiency, since
this vitamin is also important for cell division. Both types of anemia are caused by nutrient
deficiency
4. What vitamins make up the B complex? What problems are caused by a lack of these
vitamins?
Vitamins of the B complex are: thiamin, or vitamin B1; riboflavin, or vitamin B2, and niacin
(B3), which are essential in the composition of the hydrogen acceptors FAD, NAD and
NADP of the energy metabolism; pyridoxine, or B6; and cyanocobalamin, or vitamin B12.
Deficiency of vitamin B1 causes beriberi, or loss of appetite and fatigue. The lack of vitamin
B2 causes mucosal injuries in the mouth, tongue and lips. Deficiency of niacin causes
nervousness, digestive disturbances, loss of energy and pellagra. Lack of vitamin B6 causes
skin lesions, irritation and convulsions. Vitamin B12 acts together with folic acid and its
deficiency causes cell division disruptions leading to pernicious anemia (a type of
megaloblastic and nutrient deficiency anemia).
The absorption of vitamin B12 depends on another substance called the intrinsic factor,
which is secreted by gastric mucosa.
5. What is the role of vitamin C in the body? What damage is caused by a lack of vitamin
C? Why was this deficiency also known as “sailors' disease”?
Vitamin C, or ascorbic acid, is involved in the metabolism of collagen and is necessary for
the integrity of blood capillaries.
Scurvy is the disease caused by a lack of vitamin C. It is characterized by tissue lesions in the
skin, lips, nose and joints. Scurvy, or scorbutus, was also known as sailors' disease because in
the past, during sea voyages, it was difficult to obtain food that contained vitamin C on
board, such as citrus fruits. As a result, the sailors became ill with scurvy.
6. Why should foods containing vitamin C not be cooked?
To obtain vitamin C, for example, from an orange dessert, the vitamin-containing food
cannot be subject to high temperatures (cooking), since vitamin C is thermolabile, meaning
that it is deactivated by heat.
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7. What is the relationship between vitamin D and sunlight?
Vitamin D, or calciferol, is synthesized in the skin through the actions of the ultraviolet range
of sunlight on precursor molecules. Later, it is transformed into its active form in the liver
and the kidneys.
8. What disease is caused by vitamin D deficiency? Which tissue does it affect?
The lack of vitamin D causes the disease known as rickets (rachitis), which is characterized
by the decalcification of bones and bone deformities. Vitamin D is fundamental for the
absorption of calcium and, as a result, it is related to bone tissue health.
9. What is the function of vitamin E? In which foods can it be found?
Vitamin E, or tocopherol, is a fat-soluble vitamin that is involved in the respiratory chain as
coenzyme, during final stage of aerobic cellular respiration. Its deficiency may cause
sterility, spontaneous abortions and muscle dystrophy.
Vitamin E is mainly found in corn oil and peanut oil, wheat germ, milk, eggs and leafy
vegetables.
10. . Why are some types of hemorrhagic diseases caused by a genetic or acquired inability
to metabolize vitamin K?
Vitamin K deficiency predisposes people to hemorrhages since this vitamin is necessary for
the formation of prothrombin during the blood clotting process.
11. What are the functions of biotin and pantothenic acid in the body? How are these
vitamins obtained?
Biotin (also known as vitamin B8) is a vitamin that is involved in the metabolism of amino
acids and other acids. Pantothenic acid (also known as vitamin B5) is important for aerobic
cellular respiration, since it is involved in the transport of acetyl and acyl radicals.
Biotin is made by bacteria that live in the human digestive tract (in a interspecific
harmonious ecological interaction) and this supply in general is enough for the body. Biotin
and pantothenic acid are found in vegetables, grains, eggs, fish, milk and lean meat.
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ii) Mineral
12. What are the main mineral salts responsible for cellular osmotic regulation?
The main ions that are involved in the regulation of the osmotic pressure in cells and
tissues are the chlorine anion, the sodium cation and the potassium cation.
13. What are the main cellular functions of potassium?
Besides being important for osmotic regulation and for the acid-base equilibrium
(pH), potassium is necessary for the excitatory mechanisms of nerves and in muscle
contraction.
14. What are some examples of mineral salts from the diet that act as coenzymes?
Magnesium, zinc and copper are examples of biological coenzymes.
15. What disease is caused by dietary iodine deficiency?
Iodine deficiency causes hypothyroidism, an abnormally low production of thyroid
hormones, which need iodine to be synthesized.
16. What is the importance of iron in the diet? What disease is caused by iron deficiency?
Iron is a component of the hemoglobin molecule and of enzymes involved in
digestion and energy metabolism. Dietary iron deficiency causes iron deficiency
anemia, an abnormally low hemoglobin concentration in the blood due to the lack of
iron.
17. How do the various types of vitamins related to skin and mucous membranes function?
If you lack vitamin A, you will become dehydrated more easily. It is believed that the
reason for this is that the functioning of sweat glands and the skin is reduced,
Vitamin B2 strengthens blood vessels throughout the body, especially capillaries in
the skin, and improves blood circulation. It is well-known that having a deficiency
causes inflammation of the lips and corners of the mouth. Vitamin B2 deficiency
causes capillaries to dilate, which increases transparency to sunlight, raising
sensitivity to external stimuli and causing extreme sensitivity to sunlight.
18. Which vitamins are associated with metabolizing fat?
The main vitamins associated with metabolizing fat are vitamin B2, niacin, and
pantothenic acid. These vitamins are coenzymes of the enzymes necessary for
metabolizing fats, so when there is a lack of them, metabolism may be impaired. A
lack of vitamin B2 in particular halts the metabolism of fatty acids and their use as
energy. While there are many vitamins associated with the metabolism of fatty acids,
this is the reason only vitamin B2 is called the “fat metabolism vitamin.” The above
vitamins, as well as vitamin B1, are also involved in the breakdown of carbohydrates.
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19. Which vitamins and minerals should pregnant women take and which they should they
avoid?
pregnant women are recommended to increase their intake of vitamins and minerals
such as vitamin A, vitamin D, folic acid, and iron in comparison to women who are
not pregnant. Vitamin D is necessary for the formation of bones. Folic acid is a
necessary nutrient for cell division and DNA replication. while there are no vitamins
pregnant women should avoid, there are some vitamins which can cause problems if
you take too much. Toxicity specific to pregnant women has been reported for
vitamin A,
7. Procaryotes and Eucaryotes.
1. Mention the prokaryotes.
▪
▪
▪
Origin – (‘ pro’ – before , ’ karyote’ – nut)
Prokaryotes are a microscopic single-celled organism which have neither a distinct
nucleus with a membrane nor other specialized organelles.
Procaryotic cells were here first and for billions of years were the only form of life on
earth.
2. What are the types of procaryotes and their differences?
▪
▪
Bacteria – Exist in most environments
Archaea (Archaebacteria) – Exist in extreme environments (hot and salty)
3. Mention the characteristics of procaryotic cell.
▪
▪
▪
▪
▪
▪
▪
Unicellular
No nucleus or membrane-bound organelles, Chromosomes in nucleoid region
Generally, has a single chromosome . ( Cellular DNA molecule or plasmid) ( this
single chromosome, usually circular, is tightly wound and compact, and the region of
the cytoplasm containing the chromosome is called the nucleoid.)
Most species of cell walls.
Main reproduction way is fission.
Smallest, most widely distributed, numerous, and metabolically divers.
Autotrophs and Heterotrophs.
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4. What are the types of procaryotes cell shapes?
▪
▪
▪
Spheres (cocci)
Rods (bacilli)
Spirals (Spirilla)
5. What are the typical cell structures of procaryotes?
▪
▪
▪
▪
▪
▪
▪
▪
Cell wall
Outermost protective capsule or slime layer.
Plasma membrane.
cytoplasm
One or more flagella.
Pili (fimbriae)
Plasmid or chromosomal DNA
Other membrane unbound things. ( e.g.:
ribosomes)
6. Describe the procaryotic cell wall’s structure and function.
▪
Structure - Sugar coated cell wall.(polysaccharides)
-Bacterial cell walls composed of peptidoglycan.
▪
▪
Function – Surround and protect cell and maintain cell shape.
Two types of bacterial cell walls – 1.Gram positive
2. Gram negative
7. What is the gram stain test?
▪
Bacteria classified in to 2 categories based on their structure of cell wall. Used
technique is Gram stain.
▪ 1 . Gram positive
2. Gram negative
8. What are the differences of gram positive and gram-negative bacteria?
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▪
Gram-positive – cell envelope , two layers (cell wall
and cytoplasmic membrane)
- After the Gram staining
procedure, they appear Violet
under a microscope.
▪
Gram-negative – cell envelope , three layers, ( Outer
membrane , cell wall, and cytoplasmic membrane.)
-After the Gram staining procedure,
reddish pink under a microscope.
9. Describe the capsule.
▪
▪
▪
Capsule surround cell walls of many prokaryotes.
Structure
– polysaccharide or protein.
Function
- Allows bacteria to bind to other bacteria or to another substrate.
- Protection.
10.Describe flagella.
▪
▪
▪
▪
▪
One or several flagella on a single cell.
Long thin appendages.
Extend from the interior of the cell body.
Structure - protein
Function- locomotion ( rotary motion
of flagellum propels the cell through
fluid environment)
11.Describe pili. ( Fimbriae)
▪
▪
▪
Thick, straight Hair like projection
located on the surface of bacteria .
Structure – Protein called pilin.
Function- Sexual conjugation and
adhesion to host epithelium.
12.Do bacteria have DNA or RNA?
▪
Both, bacteria have DNA and RNA.
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13.What are the plasmids?
▪
▪
▪
▪
A small, circular, double-stranded DNA molecule located in bacterial cytoplasm.
It is physically separated from a chromosomal DNA .
It can replicate independently.
Occur naturally in bacteria and usually carry genes that are useful but not essential to
survival: e.g., genes which make bacteria resistant to antibiotics.
14.What are the importance of plasmid in molecular biology?
▪
▪
▪
▪
Easy to work with - Plasmids are a convenient size (generally 1,000- 20,000 base
pairs). With current cloning technology, it is easy to create and modify plasmids
containing the genetic element.
Self-replicating - Once you have constructed a plasmid, you can make an endless
number of copies of the plasmid by growing the plasmid in bacteria.
Stable - Plasmids are stable long-term either as purified DNA or within bacteria (as
glycerol stocks).
Functional in many species and can useful for a diverse set of applications Plasmids can drive gene expression in a wide variety of organisms, including plants,
worms, mice and even cultured human cells.
15.What are eukaryotes?
▪
▪
▪
▪
An organism consisting of a cell or cells in which the genetic materiel is DNA
in the form of chromosomes contained within a distinct nucleus.
Eukaryotes include all living organisms other than the bacteria and archaea.
Eukaryotic cells are appeared on earth long after procaryotic cells, but they
are much more advanced.
Eucaryotic organisms can be unicellular or multicellular.
16.Describe the basic structure of eukaryotic cell.
▪
▪
Outer boundaries (cell wall and plasma membrane, animal cells haven’t a cell
wall).
Cytoplasm.
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▪
▪
Membrane bound organelles.(Mitochondrion, nucleus, Golgi apparatus,
endoplasmic reticulum, lysosome, Golgi vesicles).
Genetic materials are in the nucleus.
8. VIRUS
1. Shortly describe what is a virus?
A virus is genetic material contained within an organic particle that invades living cells and
uses their host’s metabolic processes to produce a new generation of viral particles.
2. What are the contents of a virus?
• A core of genetic material either DNA or RNA
• A capsid that is surrounding by a protective coat
• Some viruses have envelop
3. What is the name of the protein coat that is around virus? Briefly describe it and write
down its values.
• Capsid
It is large macromolecular structure which serves as protein coat of virus. It protects
viral genetic material and aids in its transfer between host cells. It makes of protein
subunits called ‘’protomers’’. There are Helical capsids and Icosahedral capsids.
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4. What are the properties of viruses?
•
•
•
•
•
Obligate intrasellar parasites.
They have ultramicroscopic size ranging from 20nm-450 nm.
Their basic structure consists of protein shell surrounding nucleic acid core.
Nucleic acid can be either DNA or RNA.
They are inactive macromolecules outside the host cell and active only inside host
cell.
5. What are the things that are viruses can do and do not?
• Viruses do not grow and metabolize.
• But they infect cells and use the cell to make more viruses and they cause disease in
many organisms.
6. What are the transmission methods of viruses?
• Respiratory transmission : - Influenza A virus
• Faecal-oral transmission :- Enterovirus
• Blood-borne transmission :- Hepatitis B virus
• Sexual transmission
:- HIV
• Animal or insect vectors :- Rabies virus
7. What is the virus induced tumours?
Virus infects cell. Then Virus nucleic acid as DNA integrates into cellular genome. Virus
cause changes in cellular tumour formation.
8. What is the difference between enveloped and naked virus?
• Enveloped virus is surrounded by membrane.
• Naked virus does not have envelope.
9. Describe the viral shapes of viruses.
The shape of the virus is determined by either its capsid or its nucleic acid.
Here are two examples for shapes,
• Icosahedral has 20 triangular faces.
- Herpes simplex
- Chicken pox
- Polio
• Helix is a spiral shape.
- Rabies measles
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-
Tobacco mosaic virus
10. Shortly describe hoe the virus is classified according to the capsid.
We can describe it using 3 points.
• Helical capsids
They are long tube of proteins with genome inside. The tube made up of identical
protein subunits. The tube length reflects size of viral genome.
Eg :- Influenza virus (It is a enveloped virus with a helical nucleocapsid)
•
Icosahedral capsids
It has 20 triangular sides., Each triangle made up of at least 3 identical capsid proteins
and they are arranged in 2,3 and 5 fold symmetry.
Eg. :- Many animal viruses
•
Viruses with capsids complex symmetry
Some viruses do not fit in helical or icosahedral capsids symmetry groups. That kind
of viruses is in this category.
Eg. :- Pox viruses , Large bacteriophages
11. There are two types of phages viruses based on the genetic materials. Describe them.
RNA
• RNA is released into the host cell’s cytoplasm. Then it uses the ribosomes to produce
new viral proteins.
• Retro virus containing an enzyme called reverse transcriptase uses the RNA as a
template to make DNA. This DNA is integrated in to the host cell’s DNA.
DNA
•
•
It replicates in one of two ways.
It directly produce RNA that make new viral proteins and join with the host cell’s DNA
to produce new viral proteins
12. What is Viroid?
• They are smallest particles that are able to replicate.
• They have no capsid and they have short single strand of RNA.
• They disrupt plant metabolism and may damage an entire crop.
13. Briefly describe Enterovirus and Retrovirus.
Enterovirus
• They are single standard RNA viruses associated with several human and mammalian
diseases.
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•
•
•
It enters the body through the gastrointestinal tract. It often moves on to attack the
nervous system.
The virus can be found in the respiratory secretions and stool of an infected person.
Eg :- Polio virus
Retrovirus
• It Is a family o9f enveloped viruses that replicate in a host cell through the process of
reverse transcriptase.
• Eg. :- HIV 1 and HIV 2 (They cause AIDS)
14. Do viruses are living? Explain your answer
• No.
• They are non-living and they depends on host mechanism. Only the living
characteristic that viruses perform is “reproduction /multiplication”
15. What is the mechanism of viruses that they perform after entering to a host cell
•
•
•
•
Viral replication involves six steps: attachment, penetration, uncoating, replication,
assembly, and release.
During attachment and penetration, the virus attaches itself to a host cell and injects
its genetic material into it.
During uncoating, replication, and assembly, the viral DNA or RNA incorporates
itself into the host cell’s genetic material and induces it to replicate the viral genome.
During release, the newly-created viruses are released from the host cell, either by
causing the cell to break apart, waiting for the cell to die, or by budding off through
the cell membrane.
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16. Why 14 day quarantine period is necessary for virus (covid 19) infected person?
Because within this period infected person may subjected to the viral mechanism and the
strength and the ability of spreading the virus is high at this time period. During 14 days
infection period the infected person may show the symptoms within 7 days and most
probably starts to cure within 14 days so the person must be alone within this period by
not contacting with other healthy persons.
17. Spreading of Corona virus from an infected person to another is said to be reduced
after seven days from the initial infection. Briefly explain this statement.
•
•
•
A viral infection and the ability to spread a disease is gradually decreasing
after 7 days because the peak point of the infection is happening like in 7th day
of infection.
The strength of the virus is said to be slow down after the 7th day of infection.
Therefore the power of the virus is decreasing after the peak point so we can
say that Spreading of Corona virus from an infected person to another is
reduced after seven days from the initial infection.
18. What's the difference between a bacterial infection and a viral infection?
•
Bacteria
Bacteria are single-celled microorganisms that thrive in many different types
of environments. Some varieties live in extremes of cold or heat. Others make
their home in people's intestines, where they help digest food. Most bacteria
cause no harm to people, but there are exceptions.
Infections caused by bacteria include:
•
•
•
Strep throat
Tuberculosis
Urinary tract infections
Inappropriate use of antibiotics has helped create bacterial diseases that are
resistant to treatment with different types of antibiotic medications.
Viruses
Viruses are even smaller than bacteria and require living hosts — such as
people, plants or animals — to multiply. Otherwise, they can't survive. When
a virus enters your body, it invades some of your cells and takes over the cell
machinery, redirecting it to produce the virus.
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Diseases caused by viruses include:
•
•
•
Chickenpox
AIDS
Common colds
In some cases, it may be difficult to determine whether a bacterium or a virus
is causing your symptoms. Many ailments — such as pneumonia, meningitis
and diarrhea — can be caused by either bacteria or viruses
19. Why are viruses hard to kill?
•
The fact that they are not alive means they don't have to play by the same
rules that living things do.
9. CELL BOUNDARIES
i) Cell wall
1) Briefly explain the structure of the cell wall of a eukaryotic cell.
Eukaryotic cell wall is totally permeable for any kind of solutes. Locate as two layers namely
primary cell wall and secondary cell wall. From outside to the inside of cell wall,
1. Middle lamella- Cements adjacent cells together. Structurally made up of mostly pectin.
2. Primary cell wall- Structurally made up of cellulose matrix with hemicellulose, protein,
pectin, lignin, cutin and wax.
3. Secondary cell wall- Locate inside the primary cell wall of matured cells. Comprised of
hemicellulose and lignin.
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2) Explain briefly the structure of middle lamella.
Middle lamella is located between two cells by binding two adjacent primary cell walls together.
Main component of middle lamella is pectin. The places where the pectin layers split are known
as “intercellular spaces”.
3) How does the cell wall manage to construct connections between cells
Through plasmodesmata:
Those are microscopic channels through the cell walls and middle lamella and they enable
intercellular transport and communication between cells.
4) What is the reason for softening of fruits during ripening?
When ripening, the carbohydrate “pectin” in the middle lamella starts to digest by the enzyme
“pectinase” and then the pectin layer in the middle lamella dissolves and hardness of the cell
wall becomes less so fruits get soft.
5) Briefly explain “primary cell wall” and its components.
In all growing plant cells possesses a primary cell wall which is usually thin and extensible.
Locate inside the middle lamella. Basically made up of cellulose in addition to hemicellulose,
pectin, some proteins, lignin, cutin and wax.
Primary cell wall is a flexible layer with less hardness and it possesses an elasticity and primary
cell wall is comparatively thin.
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6) Briefly explain “secondary cell wall” and its components.
When cells get matured, secondary cell wall is formed between plasma membrane and primary
cell wall inside to the primary cell wall. Not all the plant cells contain a secondary cell wall.
This is also consist of mainly cellulose and additionally hemicellulose and lignin. Here lignin
gives an additional strength to the cell wall. Therefore secondary cell wall is thicker and
stronger than primary cell wall.
Secondary cell wall is, very hard and possesses a less elasticity when compared to primary cell
wall.
7) Describe the functions of cell wall.
1. Determine the cell shape
• By locating outside the plasma membrane and acting as the outer layer of the cell
2. Give support and mechanical strength
• Locate as two layers and mainly Secondary cell wall gives the strength and hardness to
the cell.
3. Prevents the cell membrane from bursting in a hypotonic medium.
• By acting as a protective layer outside the plasma membrane.
4. Controls the rate and the direction of cell growth and regulates cell volume.
• As it is the outermost layer of a cell
5. Act as carbohydrate storage
• Components of cell wall are reused by plants
6. Use to produce some economic products such as paper, wood
• Basically because due to its hardness
ii) Plasma membrane
1) Simply define “plasma membrane”
Plasma membrane is considered as a living membrane which located around the cytoplasm in
all living cells and separates the cytoplasm from exterior environment. This is a semi
permeable membrane because there a selective mechanism is applied when transportation
occurred through plasma membrane. Major components are lipids, protein and carbohydrates.
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2) Explain the structure of lipids in plasma membrane
Main type of lipids which the plasma membrane consists of is phospholipids. In addition it
contains cholesterol and steroids and cholesterol moles are arranged in between the two
phospholipid layers. They have arranged as two layers. So lipids provide the basic structure of
the plasma membrane. Lipid molecules in the plasma membranes are said to be amphipathic
3) What is mean by “Amphipathic”?
When a molecule contain both hydrophilic (water friendly/attracting/polar) region and also
hydrophobic (water repulsing/non polar) region in the same molecule it is said to be an
“Amphipathic” molecule.
4) “Water soluble molecules cannot go through the lipid bilayer”, Explain.
Because of large hydrophobic regions of both phospholipid and cholesterol water soluble
molecules cannot go through the lipid layer.
5) Explain the “fluid mosaic model” of plasma membrane
According to this model, the quasi-fluid nature of lipids enables lateral movement of proteins within
the overall bilayer. This ability to move within the membrane is measured as its fluidity. The plasma
membrane is composed of lipids that are arranged in a bilayer and within the membrane with the polar
head towards the outer sides and the hydrophilic tails towards the inner part. Because of this the
nonpolar tail of saturated hydrocarbons is protected from the aqueous environment. Peripheral proteins
lie on the surface of membrane while the integral proteins are partially or totally buried in the
membrane.
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6) Explain the structure of membrane proteins in plasma membrane
Membrane proteins are important in maintaining structural integrity of plasma membrane and
different membrane proteins are associated with the lipid bilayer in different ways. According to
the way that they associated there are two types of membrane proteins.
1. Peripheral membrane proteins
• are in the peripheral location
2. Integral (transmembrane) proteins
• pass completely through the membrane
• Hydrophobic regions embedded in phospholipid bilayer and hydrophilic
regions extending into intra and extracellular fluids
• Most are glycoproteins conjugated with oligosaccharides on the
extracellular sides of the membrane.
7) Explain the structure of carbohydrates in plasma membrane
Carbohydrates are located by combining in to the outer surface of the plasma membrane as
short branched chains. They have attached to both lipids and proteins. When the carbohydrates
combined to lipids they are said to be “glycolipids” and if they have combined to proteins those
carbohydrates are known as “glycoproteins”.
8) Write down the functions of plasma membrane
1.
2.
3.
4.
5.
Protection
Selectively allow substances
Respond to environment
Cell recognition
Communication by serving as external receptors for signaling molecules
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9) What process does water use to move across the plasma membrane?
The process used by water to move across the plasma membrane is osmosis. The plasma
membrane acts as the semi-permeable membrane during the process. Either of the following
two could happen during osmosis:
1. If the concentration of the solution inside the cell is higher than the concentration of
the solution in its surroundings, then water will move out of the cell, causing it to
shrink.
2. If the concentration of the solution in the surroundings is higher than the
concentration of the solution inside the cell, then water will move into the cell,
causing it to swell.
And also water moves to cells through the channels in membrane proteins.
10. Organs of the cell
i) Cell nucleus
1) What is the general definition of the “Cell Nucleus”
Comparatively large significant organelle. Genetic control center of a eukaryotic cell. Basically
spherical in shape. There may be single nucleus or more nuclei in a cell. Consists of DNA and
also RNA.
2) Briefly explain the structure of nucleus
Nucleus consists of 4 main parts.
Namely,
a) Nuclear envelope
b) Nucleoplasm
c) Chromatin
d) The nucleolus
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3) What is the structure and function of the nuclear Envelope of the nucleus?
Nuclear envelop is a double-layered membrane perforated with pores, which control the flow
of material going in and out of the nucleus. The outer layer is connected to the endoplasmic
reticulum, communicating with the cytoplasm of the cell. The exchange of the large molecules
(protein and RNA) between the nucleus and cytoplasm happens here.
4) What is the structure and function of the nucleoplasm of the nucleus.
Nucleoplasm is a jelly-like (made mostly of water) matrix within the nucleus and all the other
materials “float” inside the nucleoplasm. It helps the nucleus keep its shape and serves as the
median for the transportation of important molecules within the nucleus.
5) What are called Chromatin & Chromosomes in nucleus?
Chromosomes contain DNA in a condensed form attached to a histone protein where
Chromatin is comprised of DNA.
6) What are two types of chromatin based on their function and simply describe their
structure?
1. Heterochromatin
✓ Highly condensed
✓ Transcriptionally inactive
✓ Mostly located adjacent to the nuclear membrane
2. Eurochromatin
✓ Delicate
✓ Less condensed organization of chromatin,
✓ Located in a transcribing cell
7) What are the functions of nucleus?
1. The nucleus is often compared to the “command center,” as it controls all functions of the
cell.
2. It is important in regulating the actions of the cells for keeping the cell healthy and alive.
3. It plays an important part in creating the cell’s proteins- controls growth of the cell through
the synthesis of structural proteins, energy and nutrient metabolism
4. It is involved in important processes dealing with DNA and other genetic molecules.
5. The nucleus regulates the secretion of ribosomes, which are made in the nucleolus and are
the sites of gene transcription.
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ii) Endoplasmic reticulum
1) Briefly explain the term “endoplasmic reticulum”
Endoplasmic reticulum is a network of folded membranes that form channels. One side of this
attaches with nuclear envelop.
2) What are the two types of endoplasmic reticulum? Describe the structures of those
separately with a single labeled diagram.
There are two types. Those are smooth ER and a rough ER.
In rough ER there are ribosomes attached to the outer surface Consists of network-like tunnels
with tubules, vesicles which is held together by the cytoskeleton of the cell.
In smooth ER there are no ribosomes on it and smooth ER is more tubular then rough ER and
forms a separate interconnecting network. (Is found evenly distributed among the Cytoplasm.)
iii) Golgi apparatus
1) Describe the structure of Golgi apparatus
with a labeled diagram.
Golgi apparatus is a smooth, curvy structure.
Consists of flattened stack of membranes
(series of stacked plates) and it has a front end
and a back end. The front end is called the cis
face and the back end is called the trans face.
Golgi apparatus has cisternae, those are the
flattened membrane folds and secretory
vesicles which are what the cell discharges.
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iv) Lysosomes
1) Explain what are called “lysosomes” by their structure.
Lysosomes are membranous sacs produced by the vesicles from ER and Golgi. Consist of a
Single membrane. They are full of digestive enzymes which hydrolyze proteins, fats,
polysaccharides, and nucleic acids that operate at low pH. Can be found mostly in the cells
which perform “phagocytosis”.
v) Peroxisome
2) What is the basic structure of a peroxisome
Peroxisomes are organelles bound only by a single membrane. Peroxisomes contain enzymes
that help them carry out many of its tasks. Found mostly in liver cells.
vi) Vacuole
3) Describe the structure of a vacuole
Vacuoles are storage bubbles found in cells. Can be found in both animal and plant cells but
are much larger in plant cells. There is a membrane (tonoplast) that surrounds a mass of fluid.
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vii) Mitochondria
1) Describe about the structure of a mitochondria.
Mainly there are 6 regions that we can identify in a mitochondria. They are,
1.
2.
3.
4.
5.
6.
Outer membrane
Inner membrane
Inter membrane space
Translocation contact site
Matrix
Cristae
The outer membrane consists of 40% lipids and 60 % proteins and the inner membrane is
made up of 20% lipids and 80% proteins. The electron transport enzymes, proton secreting
proteins are virtually buried in the core of the inner membranes.
Matrix contains hundreds of different enzymes and it also contains small amounts of
mitochondrial DNA genome, special mitochondrial ribosomes, tRNAs and various
enzymes that required for the expression of the mitochondrial genes.
Mitochondrial DNA (mtDNA) are circular, double-stranded structures of molecules in
higher eukaryotes.
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vii) Ribosome
1) Explain the structure of a ribosome.
Ribosomes are single membrane organelles. In prokaryotes ribosomes float free in the cytosol
and in Eukaryotes they float free in the cytosol and also in RER. They made of 2 subunits.
Prokaryotes have ribosomes that are slightly smaller than eukaryotes whereas Eukaryotes consist
of 60-S/ 40-S model and prokaryotic consists of 50-S and 30-S subunits. And also intact
ribosome referred to as 70S ribosome in Prokaryotes and 80S ribosome in eukaryotes.
viii) Functions of organelles
Single membrane bound organelles
8) Vacuole
• Isolating materials that might be harmful or a treat to the cell
• Containing waste products
• Containing water in plant cell
• Maintaining internal hydrostatic pressure or turgor within the cell
• Maintaining an acidic internal PH
• Containing small molecules
• Exporting unwanted substances from the cell.
9) Lysosome
• Breakdown of ingested substance, cell macromolecules and damaged organelles for recycling.
• Intracellular digestion
• Removal of dead cells
• Role in metamorphosis
• Help in protein synthesis
• Help in fertilization.
• Role in osteogenesis
• Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides and nucleic acid.
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10) Golgi Apparatus
• Synthesis of cell wall, plasma membrane and lysosome.
• Absorption of compounds
• Modification of proteins, carbohydrates on proteins and phospholipids.
• Act as an area for storage, processing and packing of various cellular secretions
11) Endoplasmic Reticulum(ER)
• Moving proteins and other carbohydrates to the Golgi apparatus, Lysosomes and other places
which need carbohydrates
Rough Endoplasmic Reticulum (RER)
•
•
•
•
•
Involved with protein production, protein folding, quality control and dispatch
Surface for Ribosomes
Formation of glycoprotein
Select secretary and intracellular transport
Consists of network like tunnels with tubules which is held together by the
cytoskeleton of the cell
Smooth Endoplasmic Reticulum (SMER)
•
•
•
•
Manufactures lipids oils, phospholipids and steroids in some cases the
metabolism of them and associated products
Ca2+storage
Detoxification of drug and poisons
Peroxisomes
Transfer hydrogen from different compounds and materials to oxygen in order
to create hydrogen peroxide. (specially in liver cells)
Double membrane bound organelles
12)
Mitochondria
• Production ATP
• Cellular respiration
• Calcium homeostasis
• Regulation of innate immunity
• Programmed cell death
• Stem cell regulation
• Chloroplast
• Conduct photosynthesis
• Carry out function like fatty acid and amino acid synthesis
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13)
•
•
•
•
•
Cell Nucleus
The nucleus is often compared to the Command center as it controls all functions of the cell
It is important in regulating the actions of the cells for keeping the cell healthy and alive
It plays an important part in creating the cell’s proteins controls growth of the cell through the
synthesis of structural proteins, energy and nutrient metabolism
It is involved in important processes dealing with DNA and other genetic molecules
The nucleus regulates the secretion of ribosomes which are made in the nucleolus and are the
sites of gene transcription
14) Nuclear Envelop
• The outer layer is connected to the endoplasmic reticulum, communicating with the cytoplasm
of the cell
• The exchange of the large molecules (proteins and RNA) between the nucleus and cytoplasm
happens here
15) Nucleoplasm
• Helps the nucleus keep its shape and serves as the median for transportation of important
molecules within the nucleus
16) Chromatin and chromosomes
• Preventing DNA damage
• Tightly packing of the DNA to fit into the cell
• Control the DNA replication and gene expression
• Support the DNA molecule to permit the process of cell cycle meiosis and mitosis
Non membrane bound organelles
17) Ribosomes
• When the cell needs to make protein, mRNA is created in the nucleus
• The mRNA is then sent out of the nucleus and to the ribosomes
• When it is time to make the protein, the two subunits come together and combine with the
mRNA
• The subunits lock onto the mRNA and start the protein synthesis
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18) What are the differences of Chromatin & Chromosomes?
Chromatin
Chromosomes
Composed of a nucleosomes a
complex of DNA & proteins
Condensed chromatin fibers
Thin & long fibers
Thick compact & have a ribbon like
shape
Distinctly visible during cell
division
Found through the cell cycle
19) What are the differences of Rough ER & Smooth ER?
RER
SER
Has ribosomes
Hasn’t ribosomes
Found near the cytoplasm
Found near the cell membrane
Originate from
membrane
Originate from rough ER by shedding
the ribosomes
Mainly
cisternae
nuclear
composed
of
Mainly composed of tubules
Synthesis & store lipids &
also store proteins
Synthesis & store proteins
Mainly present in protein
forming cells
Mainly present in lipid forming cells
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20) What are the difference between Lysosomes & a Peroxisome?
Lysosomes
Peroxisome
Lysosomes break down biological
polymers like proteins &
polysaccharides
Peroxisomes oxidize organic
compounds, breaking down
metabolic hydrogen peroxide
Consists of degradative enzymes
Consists of oxidative enzymes
Responsible for the digestion in
the cell
Responsible for the cell protection
of the cell against metabolic
hydrogen peroxide
Found in animals
Found in all eukaryotes
Derived from either Golgi
apparatus or endoplasmic
reticulum
Derived from the endoplasmic
reticulum & are capable of
replicating by themselves
Comparatively large in size
Comparatively small
Involved in endocytosis,
autophagy, & phagocytosis
Involved in biosynthesis of lipids &
photorespiration
Degradative reactions do not
generate energy
Oxidative reactions in peroxisomes
generate ATP energy
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21) What happens to proteins that are synthesized in RER goes to Golgi body?
• Proteins that are synthesized in the rough ER get finished in the Golgi body: sugars and
phosphates added.
• Vesicles carry proteins from the ER to the Golgi, and then from the Golgi body to the cell
membrane. Secretion to the outside world occurs by exocytosis: the vesicle fuses with the cell
membrane, releasing its contents.
• The Golgi apparatus functions in conjunction with the ER by modifying products of the ER
• The primary function is to process proteins targeted to the plasma membrane, lysosomes or
endosomes, and those that will be formed from the cell, and sort them within vesicles.
• –One side functions as a receiving dock for the product and the other as a shipping dock
• The Golgi receives materials for transportation through the cis face and sends the materials
through to the trans face once they are packaged and modified into the vesicles.
• It functions in the collection, packaging, and distribution of material.
• It is part of the endomembrane system.
22) What is the basic mechanism of secretion of Golgi?
–genes are copied into messenger RNA in the nucleus
–mRNA leaves the nucleus and attaches to ribosomes in the cytoplasm.
–the ribosomes move to the rough ER and synthesize new proteins
–proteins are transported by vesicles to the Golgi for finishing
–proteins are transported in other vesicles to the cell membrane, where they are released from
the cell.
23) What are the single membrane organelles?
Golgi bodies, ER, Lysosomes, Peroxisomes, Vacuoles
24) What is the reason of calling Rough ER?
The RER is dotted with ribosomes so it is called rough.
25) Which ER hasn’t Ribosomes?
SER
26) Which Golgi part located in front of plasma membrane?
Trans face
27) Which organelles contributes to the formation of the Lysosomes?
ER & Golgi
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11. Cell Cycle and Cell Division.
1. What is the cell cycle and what are their stages?
The sequence of stages that cell passes through between one division and the next.
• Interphase
G1 phase
S phase
G2 phase
• Mitosis
• Cytokinesis
2. What is G0 phase?
The G0 phase or resting phase is a period in the cell cycle in which cells exist in a quiescent
state. G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing
nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.
3. Why called Interphase is the resting phase?
Because the changes in the chromosomes are not visible externally during interphase.
4. Why cytokinesis is the shortest phase?
The shortest phase of cell cycle is cytokinesis, because all the previous stages help prepare
the cell to divide, so all the cell has to do is divide and nothing else.
5. Why the mitosis is called equational division?
Because mitosis is the process of the cell division in which the chromosomes replicates and
equally distribute into two daughter cells. The chromosome number in each daughter cell is
equal to that in the parent cell.
6. Why meiosis is called reduction division?
Because the number of chromosomes and amount of DNA in daughter cells in reduced to
half than that of parent cell. In meiosis diploid number of chromosomes in reduced to haploid
number.
7. Give the reason Gametes has haploid number of chromosomes?
Because gametes are formed by meiosis. In the meiosis parents cell (diploid cell) produces
four (4) haploid daughter cells.
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8. Why say Gametes are produced by meiosis?
Because the number of chromosomes is reduced into half during meiosis, gametes can fuse
(fertilization) to form a diploid zygote that contains two copies of each chromosomes, one
from each parent.
Meiosis produces haploid gametes (egg or sperm) that contain one set of 23 chromosomes.
9. Why called chromosomes are carriers of heredity?
Because chromosome contain DNA which carries the genes.
10. “Children of the same parents look different.” Explain this.
Because of the crossing over and exchange genetic material of genetic recombination taking
place during meiosis. So children have the characteristics of both parents. Therefore children
of the same parents looks different.
11. Why does child look more like one parent than the other?
Looking more like one parent than other is dependent on the gene versions each parent has.
12. Telophase is the reverse of prophase. Explain this.
In the telophase nuclear membrane and nucleolus reappear and spindle fibers disintegrate.
In the prophase nuclear membrane and nucleolus are no longer visible and spindle fibers are
appeared. So we can say telophase is reverse of prophase.
13. Why is meiosis II necessary?
The two chromosomes are not separated during meiosis I.
The cells are diploid. Therefore, in order to distribute the chromosomes equally among the
daughter cells. So that they contain half the chromosome, so meiosis II is necessary.
14. What is the difference in the daughter cells between mitosis and meiosis?
In meiosis,
Daughter cells have the half number of chromosomes of the parent cell and four (4)
haploid daughter cells are not identical to the parent cell or each other.
In mitosis,
Each daughter cell contains the same number and same quality of chromosomes. (2
diploid daughter cells).
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15. What are the difference between meiosis I and meiosis II?
Meiosis I
Meiosis II
Is a heterotypic division
Is a homotypic division.
Reduces the chromosomes number in the
daughter cell.
Equalizes the chromosomes number of
both parent and daughter cells.
Homologous chromosomes are present at
the beginning.
Individual chromosomes are present at
the beginning.
A diploid cell convert into two (2) haploid
cells.
Chromosomal cross over occur during
prophase I.
Two (2) haploid cells convert into four
(4) haploid cells.
No chromosomal cross over occurs
during prophase II.
Individual chromosomes are present in the
daughter nuclei.
Sister chromosomes are present in the
daughter nuclei.
A complex division and takes more times.
Comparatively less simple and takes less
time.
16. What is the different between mitosis and meiosis?
Mitosis
Meiosis
Involves one cell division.
Involving two cell division.
Number of chromosomes remains the
same.
Number of chromosomes in halved.
Produces two diploid daughter cells.
Produces four haploid daughter cells.
Homologous chromosome do not pair up.
Homologous chromosomes pair up to
form synapsis.
Daughter cells are genetically identical.
Daughter cells are genetically different
from the parent cells.
Chiasmata form and crossing over occurs.
Chiasmata do not form and crossing over
never occur.
Occurs in all organisms. (except viruses)
Occurs only in plant, animals and fungi.
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Create a human cell with 46
chromosomes.
Create a human cell with 23
chromosomes.
17. What are the similar things between mitosis and
meiosis?
• Occurs in plants and animal cells.
• Produce new cells.
• Start with a diploid single parent cell.
• Cell undergo DNA replication.
• Similar basic steps.
18. What are the different between prophase I and prophase II?
•
Prophase I is the initial phase of meiosis I and prophase II is the initial phase of
meiosis II.
• The main difference is that;
Genetic recombination occurs through crossing over and the “chiasmata”
formation during prophase I. whereas no genetic recombination is noticed at the prophase II.
•
The pairing of homologous chromosomes occurs in prophase I and such a process
cannot be seen in prophase II.
19. What is the different between metaphase I and metaphase II?
In metaphase I, the homologous pairs line up in the center of the cell as two lines.
In metaphase II, align the chromosomes at the equatorial plate and this is happening in the
two different cells simultaneously.
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20. How does cytokinesis in plant cells differ from that in animal cells?
In Animal cell
In plant cell
It occurs by furrow method.
It occurs by cell plate method.
The constriction in plasma lemma is
formed by contraction of microfilaments.
No constriction is formed.
Cleavage starts at the periphery and then
moves inward, dividing the cell into two
parts.
Cell plate formation start at the Centre of
the cell and grows outward, toward the
lateral walls.
Binary fission
How do cell division of prokaryotic organism?
•
•
•
•
•
•
•
There are a great many more organelles in eukaryotes, also more chromosomes.
The usual method of prokaryote cell division is termed binary fission.
The prokaryotic chromosome is a single DNA molecule that first replicates.
Then attaches each copy to a different part of the cell membrane.
When the cell begins to pull apart, the replicate and original chromosomes are separated.
Following cell splitting.
There are then two cells of identical genetic composition.
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12. Photosynthesis
1. Briefly describe about photosynthesis.
Photosynthesis is the process by which light energy is captured, converted and stored in simple sugar
molecule.
2. What is the overall reaction of Photosynthesis?
▪
Sun light
6H2O(l) + 6CO2(g) -------------------- > C6H12O6(s)+ 6O2(g)
▪
six molecules of water plus six molecules of carbon dioxide produce one molecule of
sugar plus six molecules of oxygen
3. Where the photosynthesis does not occur in a leave? Why?
▪
The upper and lower epidermal cells
▪
The upper and lower epidermal cells do not have chloroplasts
4. Why chlorophyll looks Green.
▪
Chlorophyll, the green pigment common to all photosynthetic cells, absorbs all
wavelengths of visible light except green, which it reflects to be detected by our eyes.
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5. What is the process of antenna complex?
▪
Networks of chlorophyll and accessory pigments
▪
Able to capture many available wavelengths of light
▪
Passes excited electrons on to the Reaction Center
6. What are the two models of photosynthesis?
▪
Light reaction and dark reaction.
7. Describe the Structure of the Chloroplast
o
Similar in structure to a mitochondria.
o
It Has –Outer and inner membrane
o
There is an intermembrane space between the inner membrane and the outer membrane
o
Inner membrane is folded into sacs known as thylakoids.
o
Chlorophyll is contained thylakoid sacs
o
A stack of thylakoid is called a granum
o
Grana are suspended in a fluid-filled space called the stroma
o
Two grana are connected to each other by a stroma lamella.
o
Thylakoids consists of a thylakoid membrane and a thylakoid space
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8. What are the factors that affect photosynthesis, explain how they affect photosynthesis?
o
Carbon Dioxide (CO2)
o
Water
o
Light
o
Temperature
o
Oxygen
o
Minerals
o
Structure of leaves
▪
carbon Dioxide
o
Since the amount of CO2 in the air is very less, it acts as a limiting factor for
photosynthesis
o
It is seen that, when light and temperature are not the limiting factors,
increasing CO2 concentration leads to an increase in the rate of
photosynthesis. But, beyond a certain limit, CO2 starts accumulating in the
plant and this leads to slowing down of the process.
o
•So, excessive CO2 inhibits photosynthesis especially when it starts to
accumulate.
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▪
▪
o
Water
o
When there is a reduced water intake or availability, the stomata begin to
close to avoid loss of any water during transpiration.
o
With the stomata closing down the CO2 intake also stops which affects
photosynthesis. Therefore, the effect of water on photosynthesis is more
indirect than direct
Light
o
It is one of the major
factors affecting
photosynthesis.
o
Photosynthesis
cannot occur in the
dark and the source
of light for the plants
is sunlight.
o
Three attributes of
light are important
for photosynthesis:
▪
Intensity: Photosynthesis begins at low intensities of light and
increases till it is maximum at the brightest time of the day. The
amount of light required varies for different plants.
▪
Quality: Chlorophyll most effectively absorbs red and blue
wavelengths from the entire spectrum of light. Thus, maximum
photosynthesis occurs when the plant is exposed to the light of these
wavelengths
▪
Duration: The longer the plant is exposed to light, the longer the
process of photosynthesis will continue.
The spectrum of visible light energy ranges from 350 - 790 nm
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•
•
•
Temperature
o
when CO2 and light are not limiting
factors, the rate of photosynthesis
increases with increase in temperatures
till the optimum level for that plant.
o
Beyond the optimum levels on both sides
of the normal range, the enzymes are
deactivated or destroyed and
photosynthesis stops
Oxygen
o
Optimum levels of oxygen are favorable for photosynthesis.
o
The energy generated during the oxygen respiration is needed for the process of
photosynthesis.
o
However, an increase in the oxygen levels beyond the optimum for the plant leads to
inhibition of photosynthesis.
o
This is because oxygen tends to break down the intermediaries that are formed in
photosynthesis.
o
Oxygen also completes with CO
Minerals
o
•
Presence of Mn++ and CI– is essential for smooth operation of light reactions
(Photolysis of water/evolution of oxygen) Mg++, Cu++ and Fe++ ions are important
for synthesis of chlorophyll.
Structure of leaves
o
The amount of CO2 that reaches the chloroplasts depends on structural features of the
leaves like the size, position and behavior of the stomata and the number of intercellular
spaces. Some other characters like thickness of cuticle, epidermis, presence of epidermal
hairs, amount of mesophyll tissue, etc., influence the intensity and quality of light
reaching the chloroplast.
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9.
Can we think of life on earth without photosynthesis?
It would probably be limited to microbes, especially bacteria, archaea and viruses. If all
photosynthesis was switched off today, many fungi could survive for a long time. Animals would
survive for a little while, but the food chains would collapse relatively quickly.
if photosynthesis never involved, earth would be a very different planet. There would be
less far less atmospheric oxygen, so animals wouldn't be have involved again, life would be limited
to anaerobic microorganisms.
It's hard for we to imagine photosynthesis not involving, because the sun is such a great
energy source. You can be there would still be life on earth.
10.
Explain the organization of the green leaf to succeeds in photosynthetic process
They are adapted for photosynthesis by having a large surface area to absorb energy, and contain
openings, called stomata to allow carbon dioxide into the leaf and oxygen out. Although these
design features are good for photosynthesis, they can result in the leaf losing a lot of water.
The cells inside the leaf have water on their surface. Some of this water evaporates, and the water
vapor can then escape from inside the leaf.to reduce water loss the leaf is coated in a waxy cuticle
to stop the water vapor escaping through the epidermis. Leaves usually have fewer stomata on their
top surface to reduce this water loss. The upper epidermis of the leaf is transparent allowing light to
enter the leaf. The palisade cells contain many chloroplasts which allow light to be converted into
energy by the leaf.
11.
Why does photosynthesis need light?
Light provides energy for the synthesis of glucose from carbon dioxide and water during
photosynthesis.
12.
Explain the mechanisms of stomatal closure and opening?
the mechanism of the closing and opening of the stomata depends upon the presence of sugar and
starch present in the guard cells.
In the presence of light, the guard cells of the stomata contain sugar which is synthesized by their
chloroplasts.
the sugar is soluble and increases the concentration of guard cells.
Due to higher concentration of the cytoplasm of guard cells, the water enters into these cells from
the neighboring cells by osmosis. Hence, the stomata remain open.
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13.
Is there any effect of different colors of light on the rate of photosynthesis? If yes why?
Yes, because the lights higher on the light spectrum, like red and blue would have the highest
absorbance during the photosynthesis. But blue light is absorbed not only by chlorophyll but also
by carotenoids and some carotenoids are not in the chloroplast thus some part of absorbed blue light
is not going to photosynthesis .Therefore, the highest photosynthesis rate occurs under red light the
green light would have the slowest rate because the chlorophyll inside of the leaves reflects green
light, so it would not be absorbed as much as the other colors.
14.
Do three light sources with same intensities, but different wavelengths provide same amount
of energy for photosynthesis?
Although red, green and blue quanta have different energies (different frequency), photosynthesis is
driven by the number of quanta, not by their energy.
15.
What color of light is best for photosynthesis?
The best wavelengths of visible light for photosynthesis fall within the blue range(425-450 nm) and
red range ( 600-700nm).therefore, the best light sources for photosynthesis should ideally emit light
in the blue and red ranges.
16.
Can photosynthesis occur in artificial light?
Yes, photosynthesis can occur in artificial light, provided the plant receives the correct wavelength
of the light spectrum. If the correct spectrum of artificial light is provided, then plants can do
photosynthesis.
17.
What is importance of photosynthesis?
Photosynthesis is important to living organisms because it is the number one source of oxygen in
the atmosphere. Without photosynthesis, the carbon cycle could not occur, oxygen- requiring life
would not survive and plants would die. Without photosynthesis there would be little to no oxygen
on the planet.
18.
How to contribute increase the rate of photosynthesis by stomata
Stomata control the flow of gases in and out of leaves. During the day, when air temperatures rise and
carbon dioxide levels are normal or above normal, the stomata open, allowing carbon dioxide to enter
and photosynthesis to take place. Therefore, the rate of photosynthesis is high during the day.
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