3. CELL
The cell is the living, structural and functional unit of
body.
Division of cell into three main parts
1. Plasma membrane
2. Cytoplasm
3. Nucleus
1. Plasma membrane
It forms the cell’s flexible outer surface.
It seperates the cell’s internal environment from the
external environment.
It is a selective barrier that regulates the flow of
materials into and out of a cell.
The plasma membrane has key role in communication
among cells and their external environment .
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5. CYTOPLASM
Cytoplasm consists of all the cellular containts between the
plasma membrane and the nucleus.
Two components
i) Cytosol
ii) organells.
i) Cytosol – fruid portion of cytoplasm contain
i) Water
ii) Dessolve solntes
iii) Suspended particles
Surrounded by cytosol are several different types of
organells.
ii) Nucleus
It is a large organnlle that covers most of cells DNA.
within the nucleus, each chromosome, a single 5
7. THE PLASMA MEMBRANE
It is a flexible barrier that surrounds and contains the
cytoplasma of a cell called fluid mosaic model.
The molecular arrangement of plasma membrane
contains of many proteins and lipids
The membrane lipids allow passage of several
types of lipid soluble molecules but acts on barrier
to entry or exit of charged or polar substances
Some of proteins in plasma membrane allow
movements of polar molecules and ions into and
out of the cell.
Other proteins acts as signal receptors or adhesion
molecules 7
9. THE LIPID BILAYER
The Basic Structural framework of the plasma
membrane is the lipid bilayer.
Made by Three types of lipid molecules –
(i) Phospholipids
(ii) cholesterol
(iii) Glycolipids
That contains phosphate groups
The bilayer arrangements occurs due to both polar
and nonpolar parts.
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10. ARRANGEMENT OF MEMBRANE PROTEINS
Membrane proteins are categorized as integral,
wether they are firmly enbaded in the membrane.
Integral Proteins –
Extended through the lipid Bilayer and firmly
embaded in it.
Peripheral proteins are not as firmly embaded in the
proteins.
Many glycoproteins are protrude into extracellular
fluid.
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12. FUNCTIONS OF MEMBRANE PROTEINS
Some integral membrane proteins for ion channels,
poles or holes through which specific ions, such as
K+ can flow to get into or out of the cell. Most ions
channels are selective. They allow only a single
type of ion to pass through.
Other integral proteins acts as transporters,
selectively moving a polar substance or ion from
one side of the membrane to other.
They are called receptors serve as cellular
recognition sites, as Insulin receptors bind the
hormone insulin.
Membrane glycoproteins and glycolipids serve as
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13. MEMBRANE FLUIDITY
Membranes are fluid structures, the lipids and
many of proteins easily rotate and move sideways.
Membrane fluidity is excellent compromise for the
cell.
When a needle is pushed through a plasma
membrane and pulled out, the puncture site seals
spontaneously, and cell does not burts.
Despite the great mobility of membrane lipids and
proteins in their own half of the Bilayer.
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14. MEMBRANE PERMEABILITY
A membrane is said to be permeable to substances that can
pass through it and impermeable to those that cannot.
Although plasma membrane are not completely permeable to
any substance, they permit some substance to pass more
readily than others. This property of membrane is termed
selective permeability.
Lipid layer protein of the membrane is permeable to
Nonpolar
Uncharged molecules
Such as Oxygen
Carbon dioxide
Steroids
But it is impermeable to
Ions
Large unchanged polar molecules
such as glucose
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15. It is also slightly permeable to small uncharged
polar molecules such as
- Water
- Urea a waste product from the breakdown of
Amino acids.
Transmembrane proteins that acts as channels and
transports, increase the plasma membrane’s
permeability to variety of ions and uncharged polar
molecules.
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16. GRADIENTS ACROSS THE PLASMA MEMBRANE
The selective permeability of plasma membrane allows a
living cell to maintain different concentration of certain
substance on either side of plasma membrane.
A concentration gradient is a difference in concentration
of chemical from one place to another, such as from the
inside to outside of the plasma membrane.
Oxygen molecules and sodium ions (Na+) are more
concentrated in the extracellular fluid than the cytosol.
Carbon dioxide and potassium ions (K+) are opposite.
The inner surface of the plasma membrane is more
negatively charge and the outer surface is more
positively charge. It constitutes electrical gradients.
This charged difference is termed the membrane 16
17. TRANSPORT ACROSS THE PLASMA MEMBRANE
Transport of material across the plasma membrane is
essential to the life of a cell.
Certain substances must move into the cell to support
metabolic reactions.
Other substance that have been produced by the cell for
export as
Cellular waste products
Most move out of the cell.
Classification of Transports
(i) Active process
(ii) Passive process
Substances generally move across cellular membrane.
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19. (I) ACTIVE PROCESS
In active process, cellular energy is used to drive
the substance ‘Uphill’ against its concentration or
electrical gradients.
The cellular energy used is usually in the form of
A.T.P.
(II) PASSIVE PROCESS
In passive process, a substance move down its
concentration or electrical gradient to cross the
membrane using only its own kinetic energy.
There is no energy input from the cell.
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21. KINETIC ENERGY TRANSPORT
Some substances cross cellular membrane
simply by moving through the lipid layer or
membrane channels using their own kinetic
energy (Energy of motion)
Kinetic energy is intrinsic to the particles that
are moving.
A. Diffusion
B. Osmosis
Other substance must bind to specific
transporter proteins to cross a cellular
membrane as in facilitated diffusion and
Active transport. 21
22. DIFFUSION
Def : - Diffusion (Spreading ) is a passive process in
which the random mixing of the particles in solution
occurs because of the particles kinetic energy.
Both the solutes, the dissolved substance and
solvent, the liquid that does the dissolving, undergo
diffusion.
If a particular substance is present in high
concentration in one area of a solution and in low
concentration in another area, solute molecules will
diffuse to the area of lower concentration.
They move down their concentration gradient.
After some time the particles is evenly distributed
throughout the solution & it is equilibrium. 22
23. FACTORS INFLUENCE THE DIFFUSION RATE
OF SUBSTANCES ACROSS PLASMA MEMBRANE
1. Steepness of the concentration gradient
Greater concentration greater rate of diffusion
2. Temperature
Higher the temperature faster the rate of diffusion
3. Mass of the diffusing substance
Smaller molecules more rapidily & larger the mass,
slower rate.
4. Surface Area
Larger the membrane surface area faster the rate of
diffusion.
5. Diffusion distance
Diffusion across a plasma membrane taken only a
fraction of seconds because membrane is thin. 23
24. OSMOSIS
Def : - Osmosis is the net movement of a solvent
through a selective permeable membrane
Like diffusion it is passive process
In living systems, the solvent is water which moves
by osmosis across plasma membranes from an area
of higher water concentration to an area of lower
water concentration
During osmosis, water molecules pass through a
plasma membrane in two ways.
a. Moving through lipid layer
b. Moving through integral membrane proteins that
function as water channels.
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26. TRANSPORT BY TRANSPORTER PROTEINS
FACILITATED DIFFUSION
Solutes that are too polar or highly charged diffuse
through lipid bilayer
Solutes too big to diffuse through membrane
channels can cross plasma membrane by
facilitated diffusion
Solute binds to a specific transporter on one side of
membrane & released on other side. It is passive
process
Substance transported are glucose, frauctore,
galactose and some Vitamins.
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27. ACTIVE TRANSPORT
Some polar or charged solutes that must enter or leave
body cells cannot cross the plasma membrane through any
form of passive trans part
They move Uphill against their concentration gradients by Active
transport
In this energy is required
A. Primary Active transport
Energy obtained from hydrolysis of ATP is source of primary active
transport.
Solutes actively transported are
Na+ , K+, H+, Ca2+
I - (Iodine ions), Cl-
Amino acids
It is also called pumps
Expels Na+ from cells and brings K+ in.
This transport is called sodium-potassium pump, also called Na+/K+
ATP ase. 27
28. SECONDARY ACTIVE TRANSPORT
The energy stored in Na+ or H+ Concentration
gradient is used to drive other substances across
the membrane against their own concentration
gradient, drive other substances across the
membrane
Secondary active transport from Hydrolysis of ATP.
Antiports move Na+ (or H+) and another substance
in opposite directions across the membrane.
symports move Na+ (or H+) and another substace in
same direction across the membrane.
Antiport : Ca2+ , H+ out of cells.
Symport : Glucose, amino acids into cells. 28
29. CYTOPLASM
Cytoplasm consists of all the cellular contents within the plasma
membrane except for the nucleus.
two components
1. Cytosol
2. Organells
Tiny structures that performs different functions of the cells.
CYTOSOL
The cytosol (Intracellular fluid) is fluid portion of the cytoplasm that
surrounds organelles and constitutes about 55% of the total cell
volume.
Cytosol is 75-90% water plus various dissolved and suspended
components.
These are different types of
Ions Proteins
Glucose Lipids
Amino Acids ATP
Fatty acids, Water products. 29
30. ORGANELLES
Organelles are specialized structures within
the cell that have characteristic shape.
They perform specific functions in
Cellular growth
Maintenance
Reproduction
Each types of organ has its own set of
enzymes that carry out specific reaction &
serves in Biochemical processes.
Co-oprate in Homeostasis.
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31. CYTOSKELETON
The cytoskeleton is a network of protein
filaments that extends thoughout the cytosol
Three types of filamentous proteins
1. Microfilaments
2. Intermediates filaments
3. Microtubules.
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33. CENTROSOME
Centrome located near the nucleus, of two
components: a pair of centrioes and
pericentrioles material.
Two centrioles are cylindrical structures
The tubulin complexes are the organizing
centers for he growth of the mitotic spindle,
which plays a critical role in cell division and
for microtubules formation in non-dividing cell
During cell division centrosomes replicate so
that succeeding generations of cells have the
capacity for cell division 33
34. ENDOPLASMIC
RETICULUM
A.k.a. “ER”
Connected to nuclear
membrane
Highway of the cell
Rough ER: studded
with ribosomes; it
makes proteins
Smooth ER: no
ribosomes; it makes
lipids
35. RIBOSOME
Site of protein
synthesis
Found attached to
rough ER or floating
free in cytosol
Produced in a part of
the nucleus called the
nucleolus
36. GOLGI APPARATUS
Looks like a stack of
plates
Stores, modifies and
packages proteins
Molecules transported
to and from the Golgi
by means of vesicles
38. MITOCHONDRIA
“Powerhouse of the
cell”
Cellular respiration
occurs here to
release energy for the
cell to use
Bound by a double
membrane
Has its own strand of
DNA
