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Transcript
Biology
Is a science that studies living things and provides an under standing of life.
Q : How to define life
1.
2.
3.
4.
Living things are organized .
Take materials and energy from the environment respond to stimuli .
Living thing produce and develop .
Living thing have adaptation .
1. Living things are organized .
- Cells are makeup of molecules that contain atom.
Which are the smallest units of matter that can enter into chemical combination.
- In multi cellular organisms, similar cells combine to form a tissue.
- Tissues makeup organs, in turn work together in system.
2. Living thing take materials and energy from the environment respond to
stimuli.
- Living thing find energy and nutrients by interacting with their surroundings.
- The ability to respond often results in movement .
- The ability to respond helps ensure survival of the organism and allows it to
carry on its daily-activities.
- All together, we call these activities the behavior of the organism.
3. Living thing produce and develop.
- Life comes only from life.
Every type of living thing can reproduce or make anther organism.
- There are two general methods of reproduction:a sexual: without the formation of specialized sex cells.
Sexual: which distinct sex cells are produced.
4. Living thing have adaptation.
- Living things are capable of surviving in great variety of environments.
- The term adaptations is used in two senses.
a- Short term changes in response to change in the environment.
b- The long term major changes resulting from genetic differences and
production of new varieties.
Cations
Calcium ions, Ca2+, are the most abundant cations (positive ions) in the body,
making up about 1.5% of total body weight. About 99% is found in bones and
teeth, largely in combination. They combine with phosphate ions to form calcium
phosphate which increases the rigidity and hardness of bones and the enamel in
teeth . Calcium ions are also involved in blood clotting, normal muscle
contraction and nerve activity.
1
Sodium ions, Na+, are the main cations in extracellular fluids. They affect the
transport of water through cell membranes by osmosis. They are also part of the
hydrogencarbonate buffer system. Potassium ions, k+, are the main cations in
intracellular fluids. They contribute to the transmission of nerve impulses and
muscle contraction.
Magnesium ions, Mg2+, are important because of their role in the normal
functioning of muscle and nerve tissue, bone formation and as a component of
many coenzymes.
A normal diet provides sufficient quantities of calcium, sodium, potassium and
magnesium ions.
Anions
Anions are negative ions. Chloride ions, Cl- , are important in the acid-base
balance of blood and the water balance of the body, and in the formation of
hydrochloric acid in the stomach. They are found in intracellular and
extracellular fluids.
Phosphate ions, PO43-, have more roles than any other inorganic ions in
mammals. They are important for the formation of bones and teeth, as a buffer
in blood, their role in muscle contraction and nerve impulses, as a component of
many coenzymes, for their role in transfer and storage of energy in ATP, and as
a component of DNA and RNA.
Our food consists of chemicals that are necessary to :1\ Provide energy.
2\ Rerpair tissue.
3\ Regulate body machine.
Water is essential to life :The existence of living things is dependent on the chemical and physical haracteristics
of water :1\ The temperature of liquid water rises and falls
more slowly than of most other liquids.
2\ Water has a high heat of vaporization.
3\ Water is universal solvent and facilitates
chemical reaction both outside and with in living systems.
4\ Water has a high surface tension.
5\ Unlike most substances frozen is less dense than liquid water.
6\ Water molecules are cohesive and adhesive.
7\ Water accounting 70% or more of total cell mass.
8\ The critical property of water is that it is a polar molecule , in which the hydrogen
atoms have a slight positive charge and the oxygen has a slight negative charge .
Because of their polar nature , water molecules can from hydrogen bonds with each
other or with other polar molecules as well as interacting with positively or negatively
charged ions . As a result of these interactions , ions and polar molecules are readily
soluble in water ( Hydrophilic )
2
In contrast , non polar molecules , which cannot interact with water , are poorly
soluble in an aquous environment ( Hydrophobic ).
When water ionizes , it releases an equal number
of hydrogen ( H+ ) and hydrogen ions ( OH- ) :H–O–H
H+ + OH-
Acids and Basses
Acids ( High H+ concentrantion ):Are molecules that dissociate in water , releasing hydrogen ions (H+) , so called
proton donor.
For example , an improvtant inorganic acid is hydrochloric acid ( HCL ) , which
dissociation in this manner :HCl
H+ + CLDissociation is almost complete ; therefore , this is called a strong acid . If
hydrochloric acid is added to a breaker of water , the number of hydrogen ions ( H+)
increases
Bases ( Low H+ concentration )
Are molecules that either take up hydrogen ions
(H+) or release hydroxide ions (OH-)
( accept protons ) for example , an
important
inorganic base is sodium hydroxide ( NaOH ) ,
which dissociates in this manners
NaOH
Na+ + OHDissociation is almost complete , therefore ,sodium hydroxide is called a strong base .
If sodium hydroxide is added a beaker of water the number of hydroxide ions in
creases.
PH Scale :The PH scale is used to indicate the acidity and alkalinity of a solution .A pH of
exactly 7 is neutral pH . Pure water has an equal number of hydrogen ions ( H+ ) and
hydroxide ions ( OH- ).
The pH scale ranges from 0 to 14 . A pH of 7 has an equal concentration of hydrogen
ions ( H+) and hydroxide ions ( OH- ) . Above pH 7 there are more hydroxide ions ,
and below pH 7 there are more hydrogen ions than hydroxide ions.
3
Hydrochloric acid
0.0
Stomach acid
1.0
Normal rain water
5.6
Urine
6.0
Saliva
6.5
Pure water , tears
7.0
Human blood
7.4
Sea water
8.0
Sodium hydroxide
14
Buffers keep pH steady
 The pH of our blood when we are healthy is always about 7.4 , that is just
slightly basic (Alkaline) .
 pH stability is possible because the body has built in mechanism to
prevent pH changes .
 Buffers are the most important of these mechanisms .
 Buffers help keep the pH with in normal limits because they are
chemicals or combinations of chemicals that take up excess hydrogen ions
(H+) of hydroxide ions (OH-) . for example :♦ Carbonic acid CH2CO3 is a weak acid that minimally dissociates and
then reforms in the following manner :H2CO3
H+ + HCO3♦ Blood always contains some carbonic acid and some bicarbonate ions .
When hydrogen ions (H+) are added to blood , the following reaction occurs :H+ + HCO3H2CO3
♦ When hydroxide ions (OH-) are added to blood this reaction occurs :OH- + H2CO3
HCO3- + H2O
These reactions prevent any significant change in blood pH.
4
Cell Biology
Cell biology : is the specialized branch of biology which deals with the study of
structure and function of cell organelles .
Cytology :- is the science that deals with studies the cell .
Cell differ markedly in :1. structure according to their location and activities , because they have
different job to do , for example (a cell from a piece of skin is very
different from a cell taken from a piece of bone) .
2. Cells also have a variable from shape ; for example (the white blood cell
(WBC) in human , other cell e.g. egg cells , sperm cells , nerve cells .
3. Size : e.g. egg cells can be seen with the naked eye , but the nerve cells can
be seen by the microscope .
Every cells is made up of : Cytoplasm : the living material in which various activities take place and
which many organelles are found .
 Plasma membrane :- surrounded the cytoplasm .
 Nucleus :- contain the genetic material .
Cell are divided into two classes :-
1. Prokaryotic cells :
for example , bacteria (Bacilli , cocci , spirillum) it's characters : prokaryotic cells are generally smaller and simpler than eukaryotic cells
the size about 1-5 mm .
 prokaryotic cells (bacteria) lack nuclear envelope .
 in addition to the absence of a nucleus , their genomes are less complex .
 they do not contain cytoplasmic organelles or a cytoskeleton .
 prokaryotic cells have no histone protein bound to the DNA .
 prokaryotic cells divide by (Binary fission) and they contain ribosome
(70s) .
5
2. Eukaryotic cells :for example amoeba , paramecium.
 eukaryotic cells are larger and more complex than prokaryotic cells .
 the largest and most prominent organelles of eukaryotic cells is the
nucleus , with a diameter of approximately 5 mm , which is surrounded
by nuclear membrane , the nucleolus is also present .
 The DNA is combined with histone protein .
 eukaryotic contain with a variety of membrane enclosed organelles with
in their cytoplasm .
 They contain ribosome (80s)
 Eukaryotic cells divided by either mitosis and meiosis .
6

7
Endosymbiosis
 Prokaryotic cells are far older and more diverse than eukaryotic cells.
Prokaryotic cells have probably been around for 3.5 billion years, while
eukaryotic cells arose only about 1 billion years ago. It is thought that
eukaryotic cell organelles like nuclei, mitochondria and chloroplasts are
derived from prokaryotic cells that became incorporated inside larger
prokaryotic cells. This idea is called endosymbiosis, and is supported by
these observations:
 organelles contain circular DNA, like bacteria cells.
 contain 70S ribosomes, like bacteria cells.
 organelles have double membranes, as though a single-membrane cell had
been engulfed and surrounded by a larger cell.
 organelles reproduce by binary fission, like bacteria.
 organelles
are
very
like
some
8
bacteria
that
are
alive
today.
Organic compounds of cell including four classes of molecules :1.
2.
3.
4.
carbohydrates .
lipids
proteins
nucleic acids .
Carbohydrates
 The basic formula of these molecules is (CH2O)n .
 Carbohydrates include mono saccharides (one sugar) , disaccharides
(two sugars joined together), and poly saccharides (many sugars) joined
together.
A- Mono saccharides
 Simple sugars with carbon backbone of three to seven carbon atoms .
 The best known sugars are those that six carbons (hexoses) e.g. glucose ,
fructose . Have formula (C6H12O6).
 Sugars have five carbons atoms called (pentoses) e.g. Ribose , dexoy
ribose found in nucleic acid.
 sugars are important fuel for many living organisms , their solubility in
water enable them to be transported readily in body fluids .
 glucose is the blood sugar of humans represent the most important
source of energy .
B. Di saccharide-:
 contains tow mono saccharide that have joinied by dehydration reaction .
 their sugars linked by a glycosidic bond , e. g. Lactose contains galactose
and glucose (found in milk) ; Maltose composed of two glucose molecules
(is found in our digestive tract as a result of starch digestion) ; and
sucrose contain glucose and fructose .
C. Poly saccharides :Are Made up of three or more mono saccharide linked together.
e. g.
 Glycogen and starch : are the storage forms of poly saccharides in animal
and plants cells .
 Chitin and cellulose :- are the structural forms of carbohydrates in
animal and plant cell .
Lipids
 many of these are insoluble in water because lack any polar groups .
There are four groups of lipids :A ) fat and oils :- Fats and oils provide
 The most concentrated energy reserve available to the organism .
 They contain two types of unit molecules fatty acid and glycerol .
 Some fatty acids have one or more double bonds between the carbon
atoms ((16 or 18 carbon atoms with a carboxyl group (COO-) at one
end)) which are described as unsaturated fatty acids .
 Fats have mostly saturated fatty acid (so they are solid at room
temperature ).
9



Oils tent to have unsaturated fatty acids (they are liquid at room
temperature).
Therefore , A diet rich in animal fats (saturated) is linked to the
development of diseases of the heart and major arteries .
While unsaturated fats (plant fats or oil) not to have this effect.
10
B ) Phospholipids :

They are component of cellular membranes including the plasma
membrane it consist of two fatty acids joined to polar head group.

In the presence of water , phospholipids head molecule is polarized
and the tails are not .
C ) Steroid
 The most abundant steroid in the human is cholesterol .
 Cholesterol is the precursor of several other steroids , including our
hormones such as aldosterone , which helps regulate the sodium content
of the blood and the sex hormones , which help maintain male and female
characteristics .
D ) Waxes :


Waxes are solid at normal temperature and it contain Long chain
fatty acids bonds with a long chain alcohol
In human wax is produced by glands in the outer ear canal .
Its function is to trap dust and dirt particles preventing them from
reaching to the ear drum.
Comment :-
Lipids have three major roles in cells :A. They provide an important form of energy storage.
B. Lipids , are the major components of cell membrane .
C. Play important roles in cell signaling , both as steroid hormones e.g.
(estrogen and testosterone) and as messenger molecules that convey
signals from cell surface receptors.
Proteins
1. Proteins are polymers of 20 different amino acid .
2. Amino acid are very large molecules with structural and metabolic
functions .
3. All amino acids contain two important functional groups :
A ) Carboxyl (acid) group (-COOH).
B ) Amino group (-NH2).
Both of which ionize at normal body pH , therefore , amino acid are
hydrophilic :
11
Two amino acids are joined by a condensation reaction between the carboxyl
group of one and the amino group of another .
Proteins have structural and metabolic functions :
1 - Serve as building and structural elements include :
 Actine and Myosin of muscle and other contractile systems .
 Collagens which form connective ligaments with the body .
 Kertaines which form protective converings such as skin , hairs and nails
.
2 - Proteins that regulate the numerous processes and activities of the organism
include :
 Enzymes , which modulate chemical reaction of metabolism.
 Antibodies , which provide immunity against infection.
 Hormones , e.g., insulin that regulate the glucose content of the blood .
3 - Proteins are responsible for transporting many materials through the
circulatory system .
4 - Proteins also serve as food reserves e.g. :
 Ovalbumin , which is the chief ingredient of egg white.
 Casein , the major protein in milk .
12
Enzymes
Enzymes are complex, organic colloidal, catalysts produced by living cells. All
enzymes are proteins. Some enzymes consist solely of protein for example:
pepsin, trypsin and amylase. Others have a non protein part which is essential to
their structure known as a prosthetic group. For example, the respiratory
enzyme cytochrome oxidase has an iron containing prosthetic group Other
enzymes although are consisting only of protein require the presence of a non
protein enzyme cofactor before they can function. Enzymes act as catalysts. that
is they speed up the rate of chemical reaction
Hormones
Hormones are organic chemicals produced by one set of cells that affect different
set, or chemicals produced in one part of the body that controls the activity of
other parts. Hormones are chains of peptides that are coded for by genes and are
synthesized within the cytoplasim at the ribosome, and package into vesicles at
the golgi apparatus and secreted at the plasmamembrane. There are several
types of animal hormones for example:
1 - Insulin: a hormone secreted by the pancreas that lowers the blood glucose
level.
2 – Parathyroid hormone (PTH) secreted by the four parathyroid gland that
increases the blood calcium level and decreases the blood phosphate level.
3 – Thyroxin (T4) secreted from thyroid gland that promotes growth and
development in vertebrates.
4 – Testosterone which is the male sex hormone produce by testes.
5 – The ovaries produced (estrogen and progesterone) which are the female sex
hormones.
The hypothalamus and pituitary gland control the hormonal secretion of testes
and ovaries in the same manner that was described for the thyroid gland
previously.
6 – Growth Hormone (GH) or somatotropic hormone: If too little GH is
produced during childhood the individual comes a pituitary dwarf and if too
much is produced, the individual is a pituitary giant. In both instances the
individual has normal body proportion.
7 - Prolaction (PRL): produced in quantity only after child birth. In causes the
mammary glands in the breasts to develop and produce milk. It also plays a role
in carbohydrate and fat metabolism.
8 - Melanocyte – stimulating hormone (MSH): It was stimulated melanocytes to
increase their synthesis of melanin.
13
Proteins have four levels of structures :
1 - Primary structure :
Is the sequence of the amino acids joined by peptide bonds.
2 - Secondary structure :
 Is the regular arrangement of amino acids within localized regions of poly
peptides.
 There are two types of it : α he lix and β sheet .
 Secondary structures are held together by hydrogen bonds between the
CO and NH groups of peptide bonds.
3 - Tertiary structure :
Is the folding and twisting of the polypeptide chains , that is maintained by
various types of bonding between the R groups.
4 - Quaternary level of structure :
It consists of the iteractions between different polypeptide chains in proteins
composed of more than one polypeptide.
Hemoglobin chains , e.g. , is composed of four polypeptide chains.
14
Nucleic acids
A\ Two major kinds of nucleic acid are found in living things deoxyribonucleic acid
or DNA and ribonucleic acid or RNA.
B\ Each o these is a linear , unbranched polymer.
C\ The monomers is nucleic acids are nucleoties which composed of : Five carbon sugar ( pentose ) : ribose (RNA) deoxyribose (DNA)
 Nitrogen bases (purine , pyrimidine ). DNA contains tow purines
(adenine, guanine ) and tow pyrimidines (cytosine and thymine ).
Adenine , guanine and cytosine are also present in the RNA , but RNA
contains Uracil instead of thymine.
 One , two or three phosphate groups.
DNA
DNA is doubled strander molecule consisting of two polynucleotide chains
running in opposite direction.
There is a relationship , called complementarity between bases forming a rung
, if one base of pair adenine , the other must be thymine , if one base is
guanine the other must be cytosine (figure 3.18).
Watson and Crick deduced this structure in 1953.
DNA has a unique role as genetic material.
It transmits the genetic massage from generation to generation and from cell to
cell in an individual.
In eukaryotic cells DNA is located in the nucleus.
RNA
*
RNA is usually occurs in single stranded from different types of RNA
participate in a number of cellular activities:1. Messenger RNA ( mRNA ) : carries information from DNA to the ribosome
, where it serves as a template for protein synthesis.
2. Tow other types of RNA ( 2 ribosome RNA (rRNA) , and 3 transfer RNA
(tRNA)) are involved in protein synthesis.
* RNA found in both the nucleus and cytoplasm
15
ATP (Adenosine triphosphate)
•
•
ATP is a nucleotide in which adenosine is composed of adenine and ribose
three phosphate groups attached to ribose (the pentose group).
ATP with unstable phosphate bonds , is the energy currecy of cells .
(hydrolysis) ATP
H 2O
ADP + P + energy
Vitamins :
 Normal metabolic activity depends on very small amount of more than a
dozen organic substances called Vitamins.
 A vitamin is the general term for a number of chemically unrelated ,
organic substances that occur in may foods in small amounts and are
necessary for the normal metabolic functioning (figure 2002) .
 Vitamins may be water soluble (B,C), or fat soluble (A,D,E and K).
Tools of cell biology
A.
B.
C.
D.
E.
F.
G.
The compound microscope (CM) .
Electron Microscope (EM) .
Subcellular fractionation .
Growth of animal cells in culture .
Histochemistry and cytochemisty .
Auto radiography .
Viruses .
 The compound Microscope (CM)
This lab. Aims to -:
1. Identify and state the function of the primary part of a compound
Microscope .
2. Learning how to : (a) carry and used a microscope , (b) focus a
microscope , (c) prepare a wet mount , (d) determine the magnification of
field of view .
Introduction :
The light M. remains a basic tool of cell biologists with technical improvements
allowing the visualization of ever increasing details of cell structure . There are
several different types of light M. are routinely used to study various aspect of
cell structure .
1. Simple light M. (single lensed M.) magnified up to 300X (times) their
actual size .
2. Compound light microscope (the subject of this lab.) magnified up to
1000X (times) .
3. The bright field microscope .
4. Phase contrast microscope .
5. Differential interference contrast microscope .
6. Video-enhanced differential interference contrast microscope .
16
7. Fluorescence microscope .
8. Confocal microscope .
 Electron Microscope (EM)
This Lab. Aims to : to identify the EM and how to use it .
Introduction :
Because of the limited resolution of the light microscope , analysis of the details
of the cell structure has required the use of more powerful microscope
techniques , namely Electron Microscope , which was developed in 1930 and first
17
applied to biological specimens by Albert claude , Keith porter , and George
palade in the 1940 and 1950 .
There are two types of (EM) :
1. Transmission electron Microscope (TEM) :
An electron microscope that form an image by passing an electron beam through
a specimen and focusing the scattered electron with magnetic lenses .
2. Scanning Electron Microscope (SEM):
An electron microscope that scan a beam of electron over the surface of a
specimen and form an image of the surface from the electrons . the most medical
investigations are used (TEM) more then (SEM) .
18
(1)
(2)
(3)
(4)
(5)
Electron gun
The upper part of the column containing the condenser lenses
The specimen area with CompuStage
The lower part of the column with the image-forming lenses
The lower part of the column with the image-forming lenses and the
projection chamber
(6) The microscope controls are situated on two movable control panels
(7) Detector systems which are embedded into one single system, with one or
two monitor(s), one keyboard and one mouse
(8) The X-ray detector for Energy Dispersive Spectroscopy (EDS) is at the
specimen area and its cooling tank can be seen
(9) Wide angle CCD camera or High-Angle Annular Dark Field (HAADF)
detector for STEM is located just above the viewing chamber at the ‘35
mm port’
(10) Bright Field (BF) and Dark Field (DF) detectors for STEM are located
underneath the viewing screen
19
Principle:
The electron microscope can achieve a much greater resolution than
that obtained with light microscope, because the wave length of
electron is shorter than of light. Thus, under optimal conditions, the
resolving power of the electron microscope is approximately 0.2 nm.
(Resolution is the ability of microscope to separate or distinguish
between small object that are closed together).
TEM in principle is similar to the observation of stained cells with the
light microscope. Specimens are fixed and stained with salt of heavy
metals which provide contrast by scattering electrons.
Systems of TEM
The Whole EM can be divided into four basic systems:
1 – Illumination systems (High Voltage)
A- V- shape tungsten filament: is heated about 2100 °C. The filament
is housed in a metal cathode shield (gun cap) having a 1-2 mm. Hole
concentrated at the base near the filament tip. This whole unit that
accelerates the electrons down to the column is called the electron
gun.
B- Condenser lens: is electron magnetic lens, used to four the electron
beam into the specimen.
C- A mechanical stage: It is lies with in the specimen chamber allows
lateral movement of the specimen just as with the light microscope
2 – Imaging systems (Lenses)
The most critical lens in the image-forming objective
electromagnetic lens just below the specimen, two or more lenses
below this magnify the image and project it on the fluorescent screen.
20
3 – The pumping systems:
EM have two stage rotary pump setup separately together with its
driving motor, and the oil diffusion pump, provide for pumping down
and for vacuum measurement.
Outline of typical preparation:
1 – Tissue removal: As quickly as possible or practical.
2 – Fixation: Immediate tissue sliced or diced in fixative – 2%
glutaraldehyde PH=7.4 for 2h.
3 – Wash: Excee fixative removed by rinse in balanced salt solution
such as (Na-cacodylate buffer) for (15) min (3 changes) in 4°C.
4 – Post fixation: With 1% Osmium tetra oxide (OsO4) for 2h.
(Continuouo rotation) in 20°C.
5 – Wash as number 3.
6 – Dehydration: water removed by graded series of acetone such as
follow:
25% acetone for 15 min in 4°C.
50% acetone for 30 min in 4°C.
75% acetone for over night in 4°C.
90% acetone for 30min in 4°C.
100% acetone for 30min (2 changes) in 20°C.
21
7 – Infiltration:
Propylene oxide (Ivol.) + Durcupan mix. 1 – (vol.) 2hr (continuous
rotation) in 20°C.
Durcupan mix.1 for over night in 20°C.
Durcupan mix.2 for 2h. (continuous rotation) in 20°C.
8 – Embedding: used Durcupan mix.2 (in Beam capsules).
9 – Polymerization: in oven 65°C for 48h.
10 – Block trimming: Tissue exposed at tip of capsule by removal of
excess plastic.
11 – Sectioning: Trimmed block with triangular glass knife oriented
in ultra microtome to slice sections less than 0.1 µm. (usual 500-800
A°). Sections must be floated off on a water surface.
12 – Mounting: Sections set on fine mesh copper "grids" 3mm in
diameter.
13 – Staining: Grids placed up side down on a drop of saturated
uranyl- Acetate, (15 min). Rinse in distilled water; repeat with lead
citrate and rinse.
14 – Examination: with TEM.
15 – Viewing-Photographic systems: Pictures can be taken by
advanced types of cameras with high resolution. Pictures can be with
two or three dimension. The pictures are then saved on the hard disk
of computer or CD's or printed by high resolution printers.
22
 Cell Fractionation
The first step in subcelluar fractionation is the disruption of the plasma
membrane , under conditions that do not destroy the internal components of the
cell , several methods are used including :1. Sonication (exposure to high frequency sound) .
2. Grinding in a mechanical homogenizer .
3. Treatment with a high-speed blender .
This means separating different parts and organelles of a cell, so that they can be
studied in detail. All the processes of cell metabolism (such as respiration or
photosynthesis) have been studied in this way. The most common method of
fractionating cells is to use differential centrifugation:
23
A more sophisticated separation can be performed by density gradient
centrifugation. In this, the cell-free extract is centrifuged in a dense solution
(such as sucrose or caesium chloride). The fractions don't pellet, but instead
separate out into layers with the densest fractions near the bottom of the tube.
The desired layer can then be pipetted off. This is the technique used in the
Meselson-Stahl experiment (module 2) and it is also used to separate the two
types of ribosomes. The terms 70S and 80S refer to their positions in a density
gradient.
D. Growth of animal cells in culture : Animal cell culture are initiated by the dispersion of a piece of tissue into
suspension of its components cells , which is then added to a culture dish
containing nutrient media .
24
 Bacteria and Most animal cell types attach and grow on the plastic
surface of dishes used for cell culture .
 In addition to slats and glucose , the media used for animal cell cultures
contain various amino acids and vitamins , which the cells can not make
for themselves .
 The growth media for most animal cells in culture also include serum ,
which serves as a source of polypeptide growth factors that are required
to stimulate cell division .
E. Histochemistry and cytochemistry : This terms are used mainly to indicate methods for localizing different
substances , lipids , proteins , carbohydrates , ions , in tissue sections .
 Several procedures are used to obtain this type of information , most of
them based on specific chemical reactions between macromolecules , both
methods usually produced in soluble colored or electron dense
compounds that enable the localization of specific substances by means of
light or electron microscopy .
 Several ions (e.g. irons and phosphate) have been localized in tissue with
these methods .
F. Auto radiography : Cells are incubated with molecules that will be specifically in corporated
into certain cell constituent .
 These molecules are radioactively labeled that are they contain one or
more several atoms that are radioactive isotopes . e.g. thymines is found
in the DNA but not in RNA , so incorporated of thymine in to cells
indicates specifically that DNA synthesis is occurring .
G. Viruses :Are the smallest infectious agents (20-300 nm in diameter), containing as their
genome a molecule of either RNA or DNA. All viruses are parasites and which
replicates within living cells. This can be a plant, animal or bacterium, most
viruses cause disease. Most of our knowledge of viruses come from work on
(bacteriophages). These are viruses that infect only bacteria.
How do viruses cause disease?
When a virus enters a cell in your body, it takes over control of it the cell is made
to stop all its normal work and start making more viruses. Eventually, the cell
bursts releasing the new viruses. Each of these new viruses will enter another cell
and reproduce, in few hours, tens of thousands of cells can be destroyed. This
destruction of cells usually results in disease. Viral diseases can often be very
serious, because there are no drugs to fight them. lt is up to the body to fight
them be making (antibodies). Viruses lack almost everything normally found in
an ordinary cell.
They have no ribosomes, nor any of the enzymes necessary for protein synthesis,
and have none of the enzymes needed for energy production, they usually
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contain only those enzymes necessary for them to invade a cell and replicate
their own genetic material (DNA or RNA) virus particles are either polyhedral
or helical or a combination of both. Viruses show two main types of the life
history 1- lytic cycle, 2- lysogenic cycle.
Bacteriophages
A bacteriophage is a virus which multiplies within living cells, in this case
bacteria. It is probable that every type of known bacterium is host to at least one
phage, although any given phage is host-specific.
Bacteriophages have peculiar structure consist of a head & a tail the head
contains nucleic acid surrounded by a protein membrane. They contain more
than 40% of DNA. Bacteriophage attack a bacterium it penetrates the
membrane with its tail and then proceeds to inject nucleic acid (DNA or RNA)
from its head into the bacterium. Multiplication takes place until the bacterium
becomes filled with phages which develop & finally are released by the brushing
of the membrane.
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The phage are of two types:1 ) Virulent (cause lytic cycle)
After penetraining & injecting the nucleic acid and passing the eclipse phase
(virus through which is visible). Then maturation phase and assembling &
developing tails (multiplication). The viruses will rupture bacterial wall in order
to release.
2 ) Temperate (non virulent cause lysogenic cycle)
Phage of this type do not destroy the bacteria but passes the same steps of the
virulent type except without destroying the bacteria. Temperate bacteriophage
change into virulent by using ultra violet rays.
Viruses and cancer:
Cancer is a family of disease characterized by .uncontrolled cell proliferation.
The growth of normal animal cells is carefully regulated to meet the needs of the
complete organism. In contrast, cancer cells grow in an unregulated manner,
ultimately invading and interfering with the function of normal tissues and
organs.
The human cancers that are caused by viruses include cervical and other
anogenital cancers (papillomaviruses) liver cancer, (hepatitis B virus), and some
types of lymphomas (Epstein-Barr virus and human 1-cell lymphotropic virus).
Retroviruse is a type of RNA viruses cause human immunodeficiency viruses
(HIV) or called (AIDS) and also cause certain forms of cancer.
Bacteria and food poisoning
Some of the bacteria that can live on our food, can also cause disease.
They do this by :1 ) Excreting toxins into the food which will poison our body, when eating this
food.
2 ) Infecting the body after being eaten with the food the food poisoning is
restricted to infection by enteric pathogens contaminating food, or ingestion of
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food containing exotoxins. These can range from sickness and diarrhea to severe
intestinal bleeding and even death. For example, salmonella spp(Typhoid & food
poisoning). Brucella melitensis (Malta fever).
Metric units of linear measurement
Unit
Abbreviation
Size
Meter
m
39.37 U.S inches
Centimeter
cm
10-2 meter
Millimeter
mm
10-3 meter
Micrometer
um
10-6 meter
Nanometer
nm
10-9 meter
Angstrom
A
10-10 meter
Dietary Carbohydrate and disease :
1- Obesity:
This is of profound public health importance because o the clearly defined Negative
effect of obesity especially when centrally distributed in relation to diabetes ,
Coronary heart disease and other chronic disease of life style.
Genetic and environ mental factors play a role In deter mining the propen sity for
obesity.
High carbohydrate food and and lack of phsical activity promote to the in creasing
rates of obesity.
2-Dental Caries :
Foods containing sugars or starch may be easily broken down by a-amylase and
bacteria in the mouth and can produce acid which in creases the risk of carrier.
3- Non-insulin Dependent Diubetes mellitus ( NIDDM)
With in all populations a family history of NIDDM is an important predis posing
factory.
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Diet and life style-relation conditions which may lead to obesity will cearly in flounce
the risk of developing NIDDM.
Foods rich in non-starch poly sacch aridy and Carbohydrate-containing foods with
alow glycemic-index appear to protect against diabetes.
4- Cardio Vascular Disease
Many genetic and life style factors are in volved in the etiology of Coronary heart.
Dietary factors may in fluence these processes direclty or Via arange of
Cardio vascular disease.
Obesity.
High in takes of some saturated fatty acid increasing carbohydrate in take
5- Gastro in testinal diseases
Obesity is an important risk bifido bacteria and lacto bacilli in the gut and thus reduce
the risk of ucut infective gastro in testinal ill nesses.
6- Cancer :
How are lipid storage disease inherited
Lipid storage disease are inherited from one or both parents who carry a defective
gene that regulates a particular protein in a class of the body's cells.
They can be inherited two ways:a. Autosomal rescessive inheritance occurs when both parents carry pass on a copy
of the faulty gene, but neither parent is affected by the disorder.
b. X-linked (or sex-linked) recessive inheritance occurs when the mother carries the
affected gene on the X chromosome that determine the child's gender passes in to her
son.
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How are these disorder diagnosed
Diagnosis is made through clinical examination, biopsy, genetic testing, mole cular
analysis of cells or tissue to dentify inherited metabolic disorder and enzyme assays
(testing a variety of cells or body fluids in culture for enzyme deficiency).
1 – Gaucher disease:- is the most common of the lipid storage diseases. It's caused
by a deficiency of the enzyme glucocerebrosidase.
Fatty material can collect in the spleen, Liver, Kidney, Lungs, brain and bone
marrow.
2 – Niemann-pick disease
Disease is actually a group of outosomal recessive disorders caused by an
accumulation of a fat and cholesterol in cells of the liver, spleen, bone marrowm
lunge and in some patients brain.
3- Fabry Disease
Alpha-galacto sidase-A deficiency cause a build up of fatty material in the autonomic
nervous system , eyes , kidneys , and cardio vascular system .
4- Farber's Disease
Also know as Farber’s lipogranulomatosis or ceramidase deficiency.
Cause an accumulation of fatty material in the toints tissues , and central nervous
system.
5- Tay-sache Disease
Also known as GM2 variant B. Caused by adeficieny in the en zyme betahexosaminidase A .Affected children appear to develop normally for first few months
of life.
6- Sandhoff disease ( Variant AB )
This is a a sever form of Tay-sachs disease occurs at the age 6 months.
7- Krabbe Disease
Gala etosylceramide lipidosis caused by deficiency of the enzyme galac to
sylceramidase.
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Plasma Membrane
" Structure and Function "
 The structure and function of cells are critically dependent on membranes
.
 Universally, a plasma membrane protects a cell by acting as. A barrier
between its Living Contents and surrounding environment .
 It regulates what goes into and out of the cell and markes the cell as being
unique to the organism .
 In multi cellular organisms, cell junctions requiring specialized features
of the plasma membranes connect cells together in specific ways and pass
on information to neighboring cells so that the activities of tissues and
organs are coordinated .
 Investigators noted that Lipid – Soluble molecules entered cells more
rapidly than water – soluble molecules.
 This promoted them to suggest that Lipid are a component of the plasma
membrane.
 The formation of biological membranes is based on the properties of
lipids , and all cell membranes share a common structural organization ,
Bilayers of phospholipids with associated proteins .
Membrane Lipids
 Lipid constitute 50% of the mass of most cell membranes , although this
proportion varies depending on the type of membrane :-
1 ) Phospholipids : The fundamental building blocks of all cell membranes, which are
amphipathic molecules , consisting of two hydrophobic fatty acid chains
linked to a phosphate containing hydrophilic head group .
 The hydrophilic (polar) heads of the phospholipids molecules face the
intercellular and extra cellular fluids .
 The hydrophobic (non polar) tail face each other in the membrane
interior .
2 ) Glycolipids : have a structure similar to phospholipids except that the hydrophilic head
is a variety of sugars Joined to form a straight or branching
Carbohydrate chain .
 Glycolipids have a protective function .
3 ) Cholesterol : is a lipid that is found in animal plasma membranes.
 cholesterol reduces the permeability of the membrane to the most
biological molecules .
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Membrane Proteins
 Proteins constituting 25 to 75% of the mass the various membranes of the
cells .
 Membrane proteins carry out the specific functions of the different
membranes of the cell .
 These proteins are divided into two general classes , based on the nature
of their association with the membrane .
1. Integral membrane proteins , are embedded directly within the lipid
bilayer .
 Many integral membrane proteins called ((transmembrane
proteins)) span the lipid bilayer with portions exposed on both
sides of the membrane .
2. Peripheral membrane proteins are not inserted into the lipid bilayer but
are associated with the membrane indirectly , generally by interactions
with integral membrane proteins .
 The carbohydrate chains of glycolipids and glycoproteins serves as the
fingerprints of the cell .
 The lipid and protein composition of the inside half differs from the
outside half .
 The carbohydrate chains of the glycolipids and glycoproteins form a
carbohydrate coat that envelops the outer surface of the plasma
membrane .
 On the side some proteins serve as links to the cyto skeletal filaments
and on the out side some serve as links to extra cellular matrix .
Membrane Protein Diversity
These are some of functions performed by proteins found in the plasma
membrane .
A. Channel Protein :

Allows a particular molecule or ion to cross the plasma membrane freely .
Cystic fibrosis an inherited disorder is caused by faulty chloride (Cl-)
channel ; a thick mucus collects in air ways and in pancreatic and liver
ducts .
B. Carrier protein :
1. Selectively interacts with a specific molecule or ion so that it can cross the
plasma membrane .
2. The inability of some persons to use energy to sodium-potassium (Na+ K+) transport has been suggested as the cause of their obesity .
C. Cell recognition protein :


Major histo compatibility complex (MHC) glycoproteins are different for
each persons , so organ transplants are difficult to achieve .
Cells with foreign MHC glycoproteins are attacked by blood cells
responsible for immunity .
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D. Receptor Protein


is shaped in such a way that a specific molecule can bind to it .
Pygmies are short , not because they do not produce enough
growth hormone , but because their plasma membrane growth
hormone receptors are faulty and cannot interact with growth
hormone .
E. Enzymatic Protein


Catalyzes a specific reaction .
The membrane protein , adenylate cyclase is involved in ATP metabolism
, Cholera , Bacteria release a toxin that interferes with the proper
functioning of adenylate cyclase ; sodium ions and water leave in testinal
cells and individual dies from severe diarrhea .
How molecules cross the plasma membrance
 The plasma membrane is semi permeable , allows some molecules to pass
through (e.g. : small , non charged , lipid – soluble molecules) .
 Plasma membrane also is often regarded as differentially permeable (or
selectively permeable) , because not all small molecules can freely pass
through it .
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1 ) Passive ways which do not use energy . involve : diffusion and
facilitated transport .
2 ) Active ways use energy : Involve ; active transport , endocytosis and
exocytosis .
1 ) Passive Ways
A) Diffusion :- occurs when molecules move from higher to lower
concentration – that is , down their concentration gradient , until they are
distributed equally , e.g. when a few crystals of dye (solute) are placed in
water (solvent) .
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 Gases can also diffuse through the lipid bi layer , this is the mechanism by
which oxygen enters cells and carbon dioxide exits cells .
 As an example , consider the movement of oxygen from the air sacs
(alveoli) of lungs to blood in the lung capillaries .
Osmosis : The diffusion of water across a differentially permeable membrane has
been given a special name it is called Osmosis .
 Osmotic pressure develops on the side of the membrane that has the
higher solute concentration .
 A thistle tube convered at the broad end by a permeable membrane
contains a 10% sugar solution and is them placed in a beaker containing a
5% sugar solution .
 Water molecules pass through membrane more readily than do sugar
molecules .
Tonicity : Tonicity refers to the strength of a solution in relation ship to osmosis .
 Cells can be placed in solutions that have the same percentage of solute
(isotonic solution) a higher percentage of solute (hypertonic solution) . or
a lower percentage of solute (hypotonic solution) , than the cell .
Isotonic Solution : Solutions that cause cells neither to gain nor to lose water , that is the
solute concentration is the same on both sides of the membrane.
 A 0.9% solution of the salt sodium chloride (NaCl) is known to be Isotonic
to red blood cells because the cells neither swell nor shrink where placed
in this solution .
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 Therefore , physician must put this point in his mind when giving blood
or fluid to the patients .
Hypertonic Solution : Solutions that cause cells to shrink or to shrivel due to loss of water .
 Any concentration with a concentration higher than 0.9% Sodium
chloride is hypertonic to red blood cells
Hypotonic Solution : Solutions that cause cells to swell or even to burst , due to an in take of
water .
 Any concentration of salt solution lower than 0.9% is hypotonic to red
blood cell .
B ) Facilitated transport :During facilitated transport , a carrier protein assists the movement of a
molecules down it's concentration gradient no energy is required .
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Active Ways
a. Active transport : Some molecules and ions can be transported across cell membrane
against their concentration gradient if the approper transport enzymes
and a source of energy are available .
 Proteins involved in active transport often are called pumps , for example
, the sodium – potassium pump carries (Na+) to the outside of the cell and
(K+) to the inside of the cell .
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c. Endocytosis
 During endocytosis , cells take in substances by vesicle formation .
 A protein of the plasma membrane in vaginates to envelop the substance ,
and then the membrane pinches off to from an intracellular vesicle .
There are Three Methods of Endocytosis
1. Phagocytosis :- means "cell eating" , occurs when large materials taken
inside the cell , such as a food particle or another cell . White blood cells
can engulf bacteria and worn- out red blood cells by phgocytosis
Digestion occurs when the resulting vacuole fuses with a lysosome .
2. Pinocytosis :- means "cell drinking" , occurs when vesicles from a round a
liquid or very small particles .

Blood cells ,and that line the kidney tubules or in testinal wall , use this
method of ingesting substances .
3. Receptor – mediated endocytosis :- is a form of pinocytosis that is quite
specific because it involves the se of a receptor protein shaped in such a way that
a specific molecule can bind to it .
A macromolecule that binds to a plasma membrane receptor is called a ligand .
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39
Cell Membrane Specialization
The lateral parts of the cell membrane can show , several specialization that
form "intercellular junctions" functions of these junctions :1. They are the sites of adhesion between adjacent cell .
2. They prevent the flow of materials through the intercellular .
3. They help in the intercellular communication .
There are Three Types of Junctions
1. Adhesion Junctions (desmosomes) : In this type , the internal cytoplasmic plaques firmly attached to
the cytoskeleton with in each cell are joined by intercellular
filaments .
 In some organs like the heart , stomach, bladder, adhesion
junctions hold the cell together.
2. Tight junctions :
 Adjacent cells are even more closely joined by tight junctions in
which plasma membrane proteins actually attach to each other
producing a zipper like fastening .
 These junctions between cells from an impermeable barrier and
prevent the flow of materials in intercellular space .
e.g. in the kidneys the urine stays within kidney tubules because the cells
are joined by tight junctions .
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3. Gap junction : It allows cells to communicate , and is formed when two in
identical plasma membrane channels join .
 The channel of each cell is lined by six plasma membrane proteins
(Hexamers) .
Functions :1. It lends strength to the cells
2. It allows small molecules and ions to pass between them .
Gap junctions are important in heart muscle and smooth muscle because they
permit a flow of ions that is required for the cells to contract .
Apical Modification of Plasma Membrane
 Microvilli :
Finger like extensions of plasma membrane that are particularly abundant on
the surface of the cells , involved in the absorption . such as the epithelial cells
lining the intestine.
 Stereocilia :
- Specialized forms of microvilli .
- The stereocilia of auditory hair cells , are responsible for hearing by
detecting sound vibrations .
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