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N5- Unit 1
How do we improve the reliability of
Repeat the experiment
the results of an experiment?
Why do we repeat experiments?
To improve the reliability of the results
How do we improve the validity of an
By improving its design. For example, having
experiment?
all the reagents at the same temperature to
start with, making sure that all conditions
are the same (controlled variable) except for
what is changed (independent/input variable).
Why do we use % or % change as a
To allow comparison between tissues which
way to compare results?
were different in their mass/ volume/ length
at the start of the experiment.
Why do we use different
To prevent cross-contamination between the
pipettes/syringes/measuring cylinders solutions.
when setting up an experiment with
If you have only one measuring cylinder, you
solutions of different concentrations? need to start measuring the least
concentrated solution first so that the cross
contamination has a limited effect.
Unit 1 – Key area 1- Cell structure
To magnify an object so it appears larger
1-Why do we use a microscope?
than it is.
2-More powerful lenses allow you to
see more/less of the sample
3-Why do we use stains?
4-Why do we use coverslips?
5-To convert 1 mm into 1 μm
(micrometer)…
6-To convert 1 μm into 1 mm
7-To calculate the total power of the
microscope
Less but in greater detail.
So that cell parts stand out.
So that the sample does not dry out.
X 1000
÷ 1000
Multiply the power of the eyepiece lens and
the power of the objective lens.
Animal cell: 1-mitochondrion, 2-cell
membrane, 3-cytoplasm, 4-nucleus, 5ribosomes.
1
Plant cell: 1-cell wall, 2-mitochondrion, 3chloroplast, 4-cell membrane, 5-cytoplasm, 6vacuole, 7-nucleus, 8-ribosomes.
2
Bacterial cell: 1-cell membrane, 2-cell wall, 3ribosome, 4-nucleoid, 5-cytoplasm, 6-plasmid
3
Fungal cell: 1-cell wall, 2-mitochondrion, 3cell membrane, 4-cytoplasm, 5-vacuole, 6nucleus, 7-ribosome.
4
5-Function of cell membrane
6-Function of cytoplasm
7-Function of nucleus
8-Function of vacuole
9-Function of ribosome
10-Function of mitochondria
11-Function of cell wall
12-Function of chloroplast
13-Function of plasmid
14-Similarity/ difference between
plant and fungal cell
15-Similarity/ difference between
animal and fungal cell
16-Plant cell wall structure compared
to fungal and bacterial cells
17- What is characteristic of a
bacterial cell compared to all other
cells?
Controls the movement of substances into
and out of the cell.
Where most chemical processes take place.
Contains genetic material which controls the
activities of the cell.
Contains cell sap and can help keep cell
structure rigid.
Where protein synthesis happens
Where most of the energy is released by
respiration
It strengthens and supports the cell.
Contain the pigment chlorophyll.
Photosynthesis happens here.
Small circular piece of DNA in bacteria.
Similar structures except that plant cell wall
is made of cellulose and fungi have no
chloroplasts.
Similar structures except that animals cells
have neither cell walls nor vacuoles.
Only plant cell wall is made of cellulose.
Absence of organelles (membrane bound structures
such as mitochondrion, vacuole, nucleus) and a
different cell wall structure to plant and fungal cells
Unit 1 - Key area 2- Transport across the cell membrane
1-Composition of the cell membrane
1- Phospholipids (in a bilayer).
2- Proteins. These can be on the inner or outer
surface of the membrane or embedded within
the membrane surface. These proteins can
help move molecules into or out of the cell.
2-Property of the cell membrane
3-Characteristics of passive transport
4-Fluid mosaic model
5-Diffusion
6-Importance of diffusion
7-Osmosis
8-Effect of osmosis on animal cells
9-Effect of osmosis on plant cells
10-In experiments, the diffusion of
substances is usually demonstrated by…
11-In experiments, osmosis is usually
demonstrated by…
It is selectively permeable (only let molecules
smaller than a certain size go through)
Passive transport happens down a concentration
gradient and does not require energy.
The molecules which form the cell membrane
move constantly with respect to each other.
Diffusion in cells is the movement of molecules
down a concentration gradient, from an area of
high concentration to an area of low
concentration
It is how gases (CO2, O2) and some other
substances, e.g. water, glucose, urea and amino
acids move in and out of cells.
O2 and glucose are needed by animal cells for
respiration.
Water and CO2 are needed by plants for
photosynthesis.
Osmosis is the movement of water molecules
down a concentration gradient through a
selectively permeable membrane.
Water loss: cells shrink.
Water gain: cells burst.
Water loss: cells plasmolysed (cell shrinks away
from the cell wall, cell wall caves in)
Water gain: cells turgid (swollen cell which does
not burst due to the support of the cell wall).
A reagent changing colour.
12-Define active transport
A change in mass of a piece of potato or a model
cell or the change of volume of a solution (visible
on a graduated tube).
Transport against the concentration gradient.
13-Requirements for active transport
Energy is required as well as protein carriers.
14-Examples of molecules and organisms
using active transport
Transport of sodium and potassium in nerve cells,
or iodine in seaweeds.
Unit1-Key area 3- Producing new cells
1-State the function of cell division
2-State the biological name for cell
division
3-State what is the store of
hereditary information?
4-What is meant by “chromosome
complement”?
5-Describe how the daughter cells
compare to the original cell
To increase the number of cells in an
organism so that growth and cell
replacement/repair can take place.
Mitosis
Chromosomes, DNA
Number of chromosomes characteristic to a
species, e.g. humans have 46 chromosomes
They have an identical set of chromosomes
which carry the same information as the
original cell.
6-Explain why it is important that the
chromosome complement of daughter
cells in multi-cellular organisms is
maintained
To obtain two identical sets of chromosomes,
the genetic material contained in a nucleus is
replicated (copied) before mitosis.
If not, cells might die or grow and/or
function abnormally.
1-Chromatids
2-Centromere (Keeps the chromatids
together)
7
8-Recognise the stages of mitosis in
an animal cell
and in a plant cell
1- Duplicated chromosomes get shorter and
fatter. The cell is ready for mitosis.
2- Chromosome are attached to spindle
fibres at the centromere and positioned at
the equator (plane at the centre of the cell).
They can be seen to be made of two
chromatids.
3- Spindle fibres contract, chromatids are
pulled apart towards opposites poles.
4- Two nuclei form at each end of the cell
5- The cytoplasm starts to divide
6- Two daughter cells are formed
Same as above except for 5:
5- New cell wall forms on a plane at the
centre of a cell.
What is meant by a “diploid cell”
Cell culture
1-Why is cell culture done?
2-What is needed for cell culture?
3-Explain how glassware can be
sterilised
Diploid cells have two matching sets of
chromosomes.
- Make food & drink (e.g. beer, wine).
- Test antibiotic, vaccines, medicine.
- Aseptic techniques.
- Appropriate medium .
- Control of other factors (e.g. availability of
oxygen, temperature, pH).
Heat glassware in an autoclave (pressure
cooker) to 121oC.
4-Explain how hands and surfaces
need to be prepared before an
experiment.
- Hands need to be washed before an
experiment to remove microorganisms from
skin.
- Surfaces are disinfected before and after
experiment to kill microbes on work area.
Hold the lid over an opened petri dish.
5-Explain how microbes can be
prevented to contaminate an opened
petri dish
6-Explain how the inoculating can be
Flame the inoculating loop.
sterilized?
7-Why are lids held onto inoculated
To prevent entry OR exit of microbes from
petri dishes with tape
agar.
Unit 1- Key Area 4 - DNA and the production of proteins
1-Describe the structure of a DNA
Double stranded/ double helix.
molecule.
Made of sub-unit called nucleotides.
Each nucleotide consists of:
- phosphate
- desoxyribose sugar
- a base (adenine, thymine, guanine or
cytosine).
Bases on each strand form complementary
pairs.
2-What holds a DNA strand together? A bond between the sugar of one nucleotide
and the phosphate of the adjacent
nucleotide.
3-What type of bond holds the two
Hydrogen bonds.
strands together to form the double
helix?
4-What is determined by the base
The genetic code. In proteins, the base
sequence?
sequence determines amino acid sequence.
5-Complementary rule
A-T and G-C.
Protein synthesis
1-What are the chemical elements
C-H-N-O and some sulfur.
found in proteins?
2-Structure of proteins is determined DNA sequence which itself determines the
by…
order of amino acids.
3-Name of the type of bond between
Peptide bond.
amino acids
4- Give 5 examples of types of
Enzymes: speed up chemical reactions.
proteins and their function
Hormones: carry chemical messages around
the body (e.g. insulin)
Antibodies: recognize molecules of invading
organisms to defend the body against
disease.
Structural: connect and support tissues (e.g.
5-Where does protein synthesis take
place?
6-What carries the sequence
information from where it is stored
(i.e. in the nucleus) to where it is
needed (ribosome)
7-Characteristics of RNA
collagen).
Receptors: participate in cell signaling.
In ribosomes in the cytoplasm.
mRNA= messenger RNA
- Single stranded
- sugar is ribose
- Uracil (U) is found in place of thymine (T).
Unit 1 –Key Area 5 – Proteins and enzymes
1- Describe a chemical reaction in
A substrate is chemically altered into a product
general terms
A catalyst is a substance which speeds up the rate
2- Explain the meaning of the term
(i.e. the speed) of a chemical reaction without being
“catalyst”.
changed or used up.
(i.e. a catalyst is neither a substrate nor a product as
it is unaffected by chemical reactions).
An enzyme is a biological catalyst made up by all living
3-State what an enzyme is.
cells. It speeds up reactions and is left unchanged.
4-Which part of the enzyme binds
The active site. The shape of the active site is
to the substrate?
complementary to that of its specific substrate.
5-Explain the word “specific” as
Each enzyme only works on one substrate because the
applied to enzymes and their
shape of the active site is only complementary to
substrate
that of its specific substrate. E.g. Amylase only breaks
down starch. Enzymes and substrates have matching
shapes like a “lock and key”.
6-Explain why enzymes are required The cell processes necessary for life would happen too
for the functioning of living cells.
slowly without enzymes.
7-Give an example of an enzyme
C-L-A-P
- Catalase: breaks down hydrogen peroxide into water
involved in a degradation reaction.
and oxygen
- Lipase: breaks down fats into fatty acids and glycerol
- Amylase: It breaks down starch into maltose.
- Pepsin: breaks down proteins into polypeptides and
amino acids.
Potato phosphorylase: in potatoes, joins molecules of
8-Give an example of an enzyme
involved in synthesis (building up)
Glucose-1-phosphate to form starch.
Enzymes are proteins.
9-State what type of molecule
enzymes are.
10-Describe the effect of
At low temperatures, enzymes do not work effectively
temperature on enzyme activity
(molecules move too slowly). Enzymes work best at a
temperature called the optimum. Beyond that
temperature, the shape of the enzyme and its active
site change which slows down reaction rate. Above a
certain temperature, an enzyme becomes denaturated,
i.e. it is irreversibly damaged.
11-Describe the effect of a range of Each enzyme has an optimum pH, i.e. a pH at which it
pH on the activity of an enzyme
works most effectively (faster rate of reaction).
Enzyme may work at other pH but the rate of the
chemical reaction that they control is usually not as
fast.
12-Explain the term “optimum” as
The conditions at which enzymes works best are called
optimum conditions: optimum pH and optimum
applied to the activity of enzymes
temperature.
13-Explain what a control is.
A repeat of an experiment to show that the effect
observed is only due to the factor being investigated
(e.g. activity of an enzyme).
Unit 1 – Key area 6 – Genetic engineering
1-State in general terms how genetic
- naturally
information can be transferred
- by genetic engineering
2-Give examples of natural genetic
- by bacterial plasmid
engineering
- by viruses
3-State in general terms how human
By transferring a piece of chromosome from
can engineer bacteria to make new
an organism to bacteria.
substances
4-Stages in genetic engineering
1- Gene from other organism cut by
1
2
enzymes.
2- A plasmid extracted from a
vector/bacterial cell is cut open.
3
3- Gene is inserted into vector/bacterial
plasmid by an enzyme.
4
5
4- Plasmid is introduced back into host
bacteria and forms a genetically modified
(GM) organism
5- Bacteria allowed to reproduce, produce
new desirable substance from information
contained in the new gene.
5-State what is the advantage of
Obtain large quantities in short time.
genetic engineering for the production
of substances from genes
6-Give examples of products of
Insulin to help treat diabetes.
genetic engineering used by humans
Human growth hormone for children who do
not make enough of their own.
Unit 1 –Key area 7 - Photosynthesis
1-Word equation of photosynthesis
2-Number of stages and their name
3-Description of first stage
4-Description of second stage
5-Explain the transfer of energy from
the light arriving at the leaf to the
formation of sugar.
Light energy
Carbon dioxide + water
→ sugar + oxygen
Chlorophyll
2 stages
Light reaction
Carbon fixation
The light energy from the sun is trapped by
chlorophyll in the chloroplasts and is
converted into chemical energy in the form
of ATP.
Water is split to produce hydrogen and
oxygen. Hydrogen attaches to hydrogen
acceptor molecules. Excess oxygen diffuses
from the cell.
A series of enzyme-controlled reactions
which use hydrogen and ATP (produced by
the light reactions) with carbon dioxide to
produce sugar.
Light energy is trapped by chlorophyll.
Light energy is then converted to chemical
energy used to regenerate ATP.
ATP goes from stage 1 to stage 2 of
photosynthesis where glucose is formed.
C-H-O
6-What are the elements found in a
carbohydrate?
7-What are the 3 fates of the glucose - used directly in respiration to provide
produced by photosynthesis?
energy for cell processes.
- converted to a storage carbohydrate, e.g.
starch.
- converted to a structural carbohydrate,
e.g. cellulose.
8-How are factors affecting starch
By testing leaves with starch.
usually investigated?
9-Chlorophyll?
Name of a green pigment found in
chloroplasts which captures light energy.
10-Describe the process of
Raw materials: carbon dioxide and water
photosynthesis in terms of raw
Products: oxygen (waste) and sugar (glucose)
materials and products.
11-Explain what is meant by a limiting
Something which, when in short supply, will
factor and describe the main limiting
slow down or stop photosynthesis resulting in
factors in the process of
the decrease of growth.
photosynthesis.
Main limiting factors are: carbon dioxide
concentration, temperature and light
intensity,
Unit 1- Key area 8 - Respiration
1-State 5 reasons why living cells need
energy.
2-Give an example of an energy
transformation in a plant and in an animal.
3-State what cells need in order to
release the energy from food.
4-Describe aerobic respiration in terms
of a word equation
5-What is produced by all respiring
animals and plants?
6-What is the link between energy
producing and energy demanding
reactions?
7-Write the equation of ATP breakdown
and regeneration
8-How many ATPs are regenerated during
aerobic respiration?
9-Breakdown of ATP production during
aerobic respiration
10-Which cells need lots of mitochondria?
11-State what is produced by respiration
in addition to carbon dioxide
12-Give another word for anaerobic
respiration in plants and yeast
13-Characteristic of anaerobic
respiration
14-Where does anaerobic respiration take
place and how many ATPs does it release?
15-Products of anaerobic respiration in
plants and yeast (fungi)
16- Products of anaerobic respiration in
animals
17-State which of these types of food
contains more energy per gram: proteins,
fats, carbohydrates.
Cell division
Muscle contraction
Active transport
Protein synthesis
Transmission of nerve impulse
Plants: light energy → chemical energy (starch)
Animal: chemical energy (fat) → heat energy
Cells need oxygen (found in air) to release the
energy from food in “aerobic respiration”
glucose + oxygen → energy + carbon dioxide +
water
Carbon dioxide and water.
ATP
Breakdown: ATP → ADP + Pi : releases energy
Regeneration: ADP +Pi → ATP : requires energy
(Pi stands for inorganic phosphate)
38 ATP per molecule of glucose.
2 ATP are produced when glucose is broken down
into 2 molecules of pyruvic acid in the cytoplasm.
36 ATP are produced when respiration is
completed after entry of the 2 molecules of
pyruvic acid in the mitochondria.
Cells with high energy needs such as muscle cells,
nerve cells, sperm cells.
Heat energy and water will be produced by
aerobic respiration.
Fermentation.
It takes place in the absence of oxygen.
Only in the cytoplasm, 2 ATP molecules.
Ethanol and carbon dioxide.
Lactic acid
Fats contain about twice as much energy as
proteins and carbohydrates (sugars, starch)