Cell membranes are composed of lipids (45%), proteins (45%), and carbohydrates (10%). Lipids form a bilayer with hydrophilic heads facing out and hydrophobic tails facing inward. Membrane proteins can be peripheral or integral. Peripheral proteins attach to lipid heads while integral proteins span or embed within the membrane. Together, lipids and proteins give cell membranes a fluid mosaic structure and allow them to perform important functions like selectively regulating transport into and out of the cell.

1. CELL BIOLOGY
BY
Streaks

2. • BIOCHEMISTRY IS A SCIENCE
CONCERNED WITH THE CHEMICAL BASIS
OF LIFE

3. Cell is structural and functional unit of living
system
Thus Biochemistry concerned with the
chemical constituents of living cells, with the
reactions and processes they undergo.

4. Therefore biochemistry covers large areas of
• CELL BIOLOGY
• MOLECULAR BIOLOGY
• MOLECULAR GENETICS

5. Aims and Objectives
• Aim of biochemistry is to describe and explain
in molecular term, all chemical processes of
living cells.
• The major objective is, the complete
understanding at molecular level, of all the
chemical processes associated with living cells.

6. Cell
All organisms are built from cells,
The cell is the fundamental unit of life.
In general two types of cells exist in nature.
►prokaryotic cells bacteria and cyano bacteria (blue
green algae)
►Eukaryotic cells (protists,( including all single cell
organism, fungi, Algae, molds, protozoa) plants, and
animals. Differences are shown in table

9. Human Cell

10. Plasma (cell) membrane
STRUCTURE
• This is the boundary between
the cell cytoplasm & the
environment
• Is partially permeable
• Made up of 45% proteins &
45% phospholipids with the
remaining 10% cholesterol,
glycoprotein & glycolipids
FUNCTION
• Controls movement of
substances in & out of the
cell
• Act as recognition sites so
that the body’s immune
system can recognize its
own cells
• Acts as receptor sites for
attachment of specific
hormones &
neurotransmitters

11. Cell Wall:- (only in plants)
– It is the outer most boundary in plant cells
– It is absent in animal cells.
– Its thickens varies in different cells of the plant
• Structure:- is composed of
– (1) Primary wall
– (2) middle lamella
– (3) Secondary wall
• (1) Primary wall:- is composed of cellulose whose
molecules are arranged in criss cross arrangement.
Some amount of pectin is also present.
• (2) Middle Lamella:- is first to be formed in
between the primary walls of the neighboring cells.

12. • (3) Secondary wall:- is formed on inner surface of
primary wall. It is thick and chemically it is
composed of inorganic salts,
• Silica
• Waxes
• Lignin and cutin etc
• Functions:-
• It provides definite shape to the cell.
• It makes cell rigid
• It provides protection to inner parts of cell
• It does not act as a barrier to the materials
passing through it.

13. A) Cell organelles
1. Nucleus
2. Mitochondrion ( is the power house of cell)
3. Endoplasmic reticulum (ER)
4. Golgi complexes (Golgi apparatus)
5. Lysosomes
6. Peroxisomes
7. Cytoskeleton
a) Microtubules b) Microfilaments c)Micro
trabeculae
B) Cytoplasm (cytosol)

14. Nucleus
STRUCTURE
• Largest organelle - 10um diameter
• Surrounded by a nuclear membrane
Double membrane – outer is
continuous with the ER
• Nuclear pores in the membrane allow
the passage of large molecules in & out
(e.g. mRNA)
• Material inside the nucleus is called
nucleoplasm – contains chromatin
which makes up DNA of the cell
• A spherical structure called the
nucleolus is found in the nucleus – this
makes ribosomal RNA and assembles
the ribosomes
FUNCTION
• Acts as the control centre of the cell
through the production of mRNA and
protein synthesis
• Retains the genetic material in the
cell in the form of DNA /
chromosomes
• Manufactures ribosomal RNA (rRNA)
& ribosomes
• Starts the process of cell division

15. Endoplasmic Reticulum
STRUCTURE
• Complex system of double
membranes continuous with the
nuclear membrane
• Fluid filled sacs between the
membranes called CISTERNAE
which allow materials to be
transported through cell
• Two types of ER –
– smooth – has no ribosomes
attached (SER)
– rough – has ribosomes attached
(RER)
FUNCTION
• Forms an extensive transport
system
• Site of protein synthesis (Rough ER)
• Site of lipid, steroid and
carbohydrate synthesis (smooth
ER)
• Stores and transports these
materials
• Calcium ions

16. Mitochondria
STRUCTURE
• Rod shaped organelle with
double membrane
– The outer controls the entry
& exit of materials
– Inner has many folds called
cristae
• Surface of each crista is covered
with stalked particles where ATP
is made
• Mitochondria are filled with a
jelly like matrix containing
proteins, lipids, ribosomes and
loops of DNA
• Mitochondria can replicate
themselves when the cell divides
FUNCTION
• Site of aerobic respiration (Krebs
cycle)
• Responsible for production of
energy rich ATP molecules
(oxidative phosphorylation)
• No. of mitochondria reflects the
metabolic activity of the cell – so
large numbers are found in
muscle and liver cells

17. Golgi apparatus
STRUCTURE
• Small pieces of rough ER form
vesicles which join to make a Golgi
body
• Chemicals made in the ER collect in
the Golgi body where they are
modified
• Small vesicles can then be
‘pinched’ off the Golgi body
carrying new chemicals away which
are secreted when the vesicle
reaches the cell membrane
• Some of the vesicles become
lysosomes
FUNCTION
• Assembling glycoproteins (such as
mucin) by combining carbohydrate
and protein
• Transporting and storing lipids
• Formation of lysosomes
• Producing digestive enzymes

18. Ribosomes
STRUCTURE
• Small dense structures found in
huge numbers
• attached to the rough ER or free
floating in the cytoplasm
• Are about 20 – 25 nm in diameter
in eukaryotic cells
• Made up of two sub units
FUNCTION
• Synthesize proteins
• Synthesize enzymes

19. Lysosomes
STRUCTURE
• Small vacuoles formed when small
pieces of Golgi body are pinched
off
• Contain hydrolytic enzymes which
digest materials in the cell
FUNCTION
• Release enzymes which destroy
worn out organelles
• Digest materials taken into the
cell by phagocytosis
• Release enzymes to the outside
of the cell which digest materials
around the cell
• Completely break down cells
after they have died – autolysis

20. Peroxisome
Function
They have a single membrane and are small (0.3 -1.5 µm
)spherical or oval with fine network of tubules in their matrix .
Over 50 enzymes catalyzing oxidative and biosynthetic reactions
have been identified in peroxisomes from different tisssues .
Oxidation of very long chain fatty acids and synthesis of
glycerolipids ,glycerol ether lipids (plasmalogens) and
isoprenoids .
Catalase ,heme enzyme present in peroxisomes catalyses the
conversion of H2O2to water and oxygen and oxidation of
various compounds by H2O2

21. • Cytoskeleton.
Non muscle cell perform mechanical work like self
propulsion, morphogenesis, cleavage, endocytosis, Ic
transport and changing cell shape. These cellular
function are carried out by extensive Ic network of
filamentous structures constituting cytoskeleton.
Three type of filamentus structure,
1. Microfilaments (actin and myosin filaments)
2.Microtubule are composed of tubulin, a protein which
assembles into tubular structures
3. Intermediate filaments: keratins, neurofilaments

22. • Functions:
• Maintain cellular morphology, Intracellular
cellular transport, cell motility and cell division.
Cytosol:
The contents of a eukaryotic cell within the cell
membrane (excluding the cell nucleus), is referred to
as the cytoplasm.

23. The concentrations of ions such as sodium and
potassium are different in the cytosol than in the
extracellular fluid; these differences in ion levels
are important in processes such as
osmoregulation and cell signaling.
Function
Enzymes of glycolysis,
gluconeogenesis, fatty acid synthesis
etc.

24. COMPOSITION,STRUCTURE OF CELL
MEMBRANE
LECTURE 2

25. BIOLOGICAL MEMBRANES
• Major concept. To study structure, composition and
functions of plasma membrane.
• Specific objectives:
chemical composition and functions of individual
constituents (lipids, protein, carbohydrate) .
• Fluid mosaic model of memb.
• Transport function:
• Inherited disorders:

26. The cell membranes are composed
Lipids (45%) which account for almost all
the mass of biological membranes,
proteins (45%)
carbohydrates present as part of
glycoprotein's and glycolipids
• The relative proportions of proteins and lipids
vary with the type of membrane, reflecting the
diversity of biological roles

27. • Each type of cell membrane has characteristic
set of membrane lipids
• The protein composition varies
• Some membrane proteins are covalently linked
to complex carbohydrates, or one or more lipids

28. Lipids
• Lipids are the basic structural components of cell membrane.
Lipid molecules have a polar or ionic head hence hydrophilic
and the other end is a nonpolar and hydrophobic
• Types of lipids present in Bio-membranes are
• Fatty acids:- are oleic acid, archidonic acid, linoleic and
linolenic acids (50% saturated 18C and 50% unsaturated).
• Gylcero phospho lipids:- are phosphatidyl ethanol amine
(cephalin), phosphatidyl choline (lecithin), and phosphatidyl
serine.
• Sphingophospholipids:- are sphingomyclin, cerebrosides and
gangliosides
• Phospholipids & cholesterols form a lipid bilayer in which the
non-polar regions of the lipid molecules face each other at the
core of the bilayer and their polar head groups face outward

29. Proteins in the cell membrane are
• 1. Peripheral membrane proteins:-
– also called extrinsic proteins
– Exist on the surface of membranes and they are
attached by ionic and polar bonds to polar heads
of lipid.
They can be easily removed from the
membrane.
Example:
The special peripheral membrane proteins
participate in the stability of red cells are
• Spectrin
• Actin
• Ankyrin and band 4,1protein

30. • 2. Integral Membrane Proteins:-
–also called intrinsic membrane proteins)
,these proteins are deeply embedded in the
membrane
– portions of these proteins are in
vanderwaals contact with the hydrophobic
region of the membrane
–EXAMPLE
–GLYCOPHORIN
–BAND -3-PROTEIN

31. The num of protein varies from dozen to 100 in
different memb.
Many of these function as
channels, transporters, enzymes and structural
components .
• 3. Trans Membrane Proteins:-
• Some of the integral proteins span the whole
breadth of the membrane and are called trans
membrane proteins. These proteins can serve as
receptors for hormones, neurotransmitters,
tissue specific antigens, growth factors etc.

32. • An important disease that
occurs due to genetic
mutations in transmembrane
proteins is :
Cystic fibrosis, which is a
recessive genetic disorder.

34. Clinical aspects
Hereditary spherocytosis, Hereditary elliptocytosis.
There is genetic defect in shape of RBCs which lead
to inc haemlytic anaemia and jaundice
These are due to mutation in genes coding for
proteins of the membrane

35. Carbohydrates:
Many memb proteins and lipids are
glycosylated, (glycoprotein, glycolipids ) with
one or more covalently attached
oligosaccharides chains, called glycocalyx are
present.
They are attached to the protein either by
1. N-glycosidic linkage b/w
N-acetylglucosamine & Asparagine.

36. 2. O-glycosidic linkage b/w
N-acetylglucosamine & Ser or Thr.
• The variable carbohydrates components of the
glycolipids and glycoproteins on the cell surface
participate in molecular targeting and cell-cell
recognition.

37. 1. Lipid Bilayer Model:-
• Was proposed by Daveson and Danielli in 1935.
• According to this model, the plasma membrane is composed of
lipid bilayer sandwitched between two protein layers.
• This basic structure is found in all the membranes such as
those of mitochondria, chloroplasts etc.
• Lipids bilayers are oriented with their hydrophobic tails inside
the bilayer while hydrophilic polar heads are in contact with
the aqueous solution on each side.
• Not all the lipids can form bilayers.
• A lipid bilayer can form only when the cross sectional areas of
the hydrophobic tail and hydrophilic polar head are about
equal.
• Glycerophospho lipids and sphingo lipids fulfill this criteria and
hence can form bilayer.
• A lipidbilayer is about 6nm across and this is so thin that it may
be regarded as a two dimensional fluid.

38. Depending upon the nature of lipids, three types of
aggregates are formed:
• 1. Micelles; Which are spherical aggregates, having
hydrophobic groups clustered in the interior and
hydrophilic outwards. They are important in intestinal
digestion and absorption of fat.
• 2. Liposome;
In this lipid bilayer will close in on itself to form
spherical vesicles which are called liposomes.

39. Functions.
Carriers of drugs, enzymes & DNA e.g.
antibiotics, antimalarial, antiviral,
antifungal and anti-inflammatory agents .
Some drugs have longer effectiveness
when encapsulated in liposomes

41. FLUIDITY
• The fluidity of a membrane significantly affects its
functions.
• As membrane fluidity increases, so does its
permeability to water and other small hydrophilic
molecules.
• The lateral mobility of integral proteins increases as the
fluidity of the membrane increases.
The degree of fluidity depends on lipid composition &
temperature.
The cholesterol content of membranes is important.
Its insertion prevents the highly ordered packing of
fatty acyl chains and thus regulate the membrane
fluidity.

42. 2. Fluid Mosaic Model:-
• Of membrane structure proposed by singer and Nicholson
in 1972 which revealed that lipid bilayer is not
sandwithched between two protein layers.
• Instead proteins are embedded in the lipid bilayer in a
mosaic manner.
• The membrane proteins. Intrinsic proteins (integral)
deeply embedded and peripheral proteins loosely
attached, float in an environment of fluid phospholipid
bilayers.
• It can be compared like icebergs floating in sea water.
• According to this, cell membrane also contains charged
pores through which movements of material takes place
both by a active and passive transport.
• The cholesterol content of the membrane maintains the
fluidity.

45. • Specialized structure of plasma mamb.
1.Lipid rafts.
The exoplasmic leaflet of the lipid bilayers
enriched in cholesterol, sphingolipids and
certain proteins. It plays role in signal
transduction.

46. • 2. Caveolae.
• are flask shape indentation derived from lipids
rafts and contains protein (caveoline-1). This
protein detected in caveolae include various
components of the signal transduction system
e.g insulin receptor, G protein, folate receptor
and endothelial nitric oxide synthase (eNos).

48. LECTURE 3
OSMOSIS ,TRANSPORT ACROSS CELL
MEMBRANE

49. TRANSPORT OF MATERIALS ACROSS CELL
MEMBRANE
• The compound must enter and leave the cells in an orderly
manner for normal functioning of cells.
• The plasma membranes contain proteins that specifically
recognize and carry solutes into the cell e.g. sugars, amino
acids & inorganic ions

50. • In some cases, these components are
transported against
a) The concentration gradient,
b) Electrical charge or both
• Many materials are pumped out to keep their
concentrations in the cytosol lower than in the
surrounding medium

51. • Molecules to be transported are
1. Micromolecules 2. Macromolecules.
Types of transport mechanism :
A) Passive Transport (Diffusion)
• Passive or simple diffusion
• Facilitated diffusion
B) Active transport
(a) primary active transport
(b) secondary active transport

52. Membrane Transport:-
• Lipid – soluble molecules pass through the
plasma membrane readily by dissolving in the
lipid bilayer.
• Small molecules pass through membrane pores.
The pores are positively charged and allow
anions and neutral molecules to pass through
more readily than cations.
• Large polar substances (e.g. glucose, and
aminoacids) are transported through the
membrane with the help of carrier molecules.

53. MEDIATED TRANSPORT MCECHANISMS:-
• Mediated transport is the movement of a
substance across a membrane by means of a
carrier molecules, the substances transported
are large, water soluble molecules.
• The carrier molecules have active sites that bind
with either a single molecule or a group of
similar molecules.
• Similar molecules compete for carrier molecules.
• Once all the carrier molecules are in use,
saturation occurs.

54. •Types of Mediated Transport:-
• Passive or simple diffusion
• Facilitated diffusion
• Active transport

55. • Diffusion describes the spread of particles through
random motion from regions of higher
concentration to regions of lower concentration
(down a concentration gradient).
• The concentration gradient is the difference in
solute concentration between two points divided by
the distance separating the points.
• The rate of diffusion increases with an
– increase in the concentration gradient.
– increase in temperature.
– Decrease in molecule size.
– Decrease in viscosity.
Diffusion

57. • The end result of diffusion is a uniform
distribution of molecules.
• Simple diffusion requires no expenditure of
energy nor any carrier proteins. It operates
unidirectionally.
• Small uncharged molecules such as O2 , CO2,
H2O and lipid soluble substances get
transported across the membrane through the
process of diffusion.

58. Osmosis:-
• Osmosis is the diffusion of a solvent across a selectively
permeable membrane or
• Osmosis is a term used for the diffusion of water through
cell membranes.
• When two solutions of different concentrations are
separated by a semi-permeable membrane which is
permeable to solvent molecules (water) but not to the
solute molecules.
• The solvent diffuses across the membrane from the less
concentrated to the more concentrated solution, till the
concentration of the solutions on both sides of the
membrane becomes equal. This process is called osmosis.
• Osmosis refers to the movement of solvent, but not of any
solutes present in the solution.

59. Osmotic pressure
• Osmotic pressure is a measure of the tendency of water (or
solvent) to move across the selectively permeable membrane
OR
• Osmotic pressure is the amount of hydrostatic pressure
required to prevent the osmotic transport of solvent across
the semi permeable membrane.
• The Osmotic Pressure depends on the number of solute molecules in
solution, irrespective of the size, shape or mass of the solute.
• Is- osmotic solutions have the same concentration of solute particles.
Cells placed in an isosmotic solution neither swell nor shrink.
• Hyperosomotic solutions have a higher concentration of solute
particles. Cells placed in it, they shrink.
• Hypoosmotic solutions have a low concentration of solute particles
than a reference solution and the cells placed in it swell and may lyse.

60. Facilited Diffusion:-
• (b) Facilited Diffusion:-
• It is similar to passive or simple diffusion in that solutes
move along the concentration gradient but it differs
from passive diffusion in that it require a “Carrier or
transport protein. Hence, the rate of diffusion is faster
than simple diffusion”. The process does not require
any energy.
• Mechanism of facilitated diffusion has been explained
by
• Ping – pong model. (in carbohydrates)
• Example:-
• D- fructose is absorbed from intestine by facilitated
diffusion

61. PING PONG MODEL
• Pong state
• Active sites are exposed to the exterior, when
solute binds conformational change occur ,
• Ping state
• Active sites are facing the interior of the cell
this will cause the release of solute molecules
and the protein molecule reverts to pong state
• By this mechanism inward flow is facilitated
and outward flow is inhibited

62. Transport of Glucose (Ping pong Model)

63. • Transport by Channels, Pores and Gap junction:-
• Membranes of most cells contain specific
channels..
• Membrane channels are differentiated from
membrane pores on the basis of their degree of
specificity for molecules crossing the membrane.
• Channels:-
• Channels are specific for inorganic cations and
anions.
– Channels allow the translocation of substances from
one side of the membrane to the other without
undergoing conformational changes.
– Voltage regulation, chemical regulation and regulation
by AMP are some ways in which channels function.

64. • Water Channels (Aquaporins) Aquaporins are
integral membrane proteins from a larger family of
major intrinsic proteins (MIP) that form pores in the
membrane of biological cells
Example; In collecting ductules of the kidney, the
movement of water by simple diffusion is enhanced
by movement of water through these channels.
Aquaporins are of Five types
Clinical Aspect: Mutation in gene encoding
Aquaporin-2 have been shown to be the cause of
one type of Nephrogenic diabetes insipidus
(Inheritance of two mutant genes for aquaporin-2)

65. • The mitotic acetylcholine channel is an example
of chemically regulated channel.
• Pores:- Pores are not so selective and will
allow sufficiently small molecules to pass freely
through them
– The gap junction between endothelial muscle and
neuronal cells is a cluster of small pores. Small
molecules pass between cells through gap junction..
The pores are usually maintained in an open state.
– Movements of large molecules is permitted through
Nuclear pores which are usually 90˚ A in diameter.
– The plasma membrane of gram negative bacteria
contains protein pores called porins.

66. IONOPHORE
• An ionophore is a lipid-soluble molecule usually
synthesized by microorganisms to transport ions across the
lipid bilayer of the cell membrane. There are two broad
classifications of ionophores.
• Mobile ion carriers
• chemical compounds that bind to a particular ion,[1]
shielding its charge from the surrounding environment, and
thus facilitating its crossing of the hydrophobic interior of
the lipid membrane.
• Channel formers[2]
that introduce a hydrophilic pore into the membrane,
allowing ions to pass through while avoiding contact with
the membrane's hydrophobic interior.

67. CARRIER IONOPHORES

68. Ionophores
• Ionophores disrupt transmembrane ion
concentration gradients, required for the
proper functioning and survival of
microorganisms, and thus have antibiotic
properties. They are produced naturally by a
variety of microbes and act as a defense
against competing microbes. Many antibiotics,
particularly the macrolide antibiotics, are
ionophores that exhibit high affinities for Na+
or K+

69. Gap Junction
It is made of protein called connexin.
Certain cells have specialized region on their memb for
intracellular communication which are in close
proximity.
They mediate and regulate the passage of ions and
small molecules through a narrow hydrophilic core
connecting the cytosol of adjacent cells.
Mutations in genes encoding connexin is a associated
with the number of conditions like cardiovascular
abnormalities, a type of deafness.

70. GATED CHANNELS
• . These channels permit facilitated diffusion by
opening or closing according to the needs of the
cell, hence are called gated channels. They are;
• (i) ligand – gated
• (ii) mechanical gated
• (iii) voltage gated
• All the channels are selective that is the structure
of the protein admits only specific types of
molecules through the pores.

71. (i) Ligand – gated channels:-
• In this a specific molecule binds to a receptor and opens the
channel. The binding site may be on the extracellular or
intracellular side of the channel.
• External ligands bind to a site on the extracellular side of the
channel protein. Example are acetycholine receptor is present in
post synaptic membrane.
• It is a complex of five subunits having a binding site for
Acetylcholine
• Acetylcholine released from the pre – synaptic region binds with
the binding site of post synaptic region, which triggers the
opening of the channel and influx of Na+.

72. • Internal ligands bind to a site on the
intracellular side of the channel protein.
Examples are “Second messengers” such as
cyclic AMP (cAMP) and cyclic GMP (cGMP)
that regulate channels involved in the
initiation of impulses in neurons that respond
to odours and light respectively

73. • Voltage Gated Channels:-
• These channels open or close in response to changes
in membrane potential. As impulse passes down a
neuron, the reduction in the voltage opens sodium
channels in the adjacent portion of the membrane.
This allows the influx of Na+ in to the neuron and
thus the nerve impulse is propagated.
• Mechanically Gated Channels:-
• Mechanical deformation of the cells induces the
stretch receptors to open up ion channels that result
in generation of nerve impulse. A good example is
bending of the cilia like projections on the hair cells
of the inner ear by sound waves which opens up ion
channels that lead to the generation of nerve
impulses. The brain interprets the nerve impulse as
sound.

74. Transport of Macromolecules:-
• The mechanism of transport of
macromolecules such as proteins, hormones
immunoglobulins, LDL and even viruses takes
place across the membrane by two
mechanisms
• Exocytosis
• Endocytosis

75. Exocytosis:-
• Most cells release macromolecules to the exterior by the
process called exocytosis
• Mechanism:- the inner membrane of the vesicle fuses with the
outer plasma membrane while cytoplasmic side of vesicle
fuses with the cytoplasmic side of plasma membrane thus the
contents of vesicles are externalized
• The process induces a local and transient change in Ca++
concentration which triggers exocytosis. They fall in 03
catagories.
• i) They can attach to the cell surface and become peripheral
proteins e.g. antigens.
• ii) They can become part of extracellular matrix e.g. collagen
and glucosaminoglycans (GAGI)
• iii) Hormones like insulin, parathormone (PTH) and
catacholamines are all packaged in granules, processed with in
cells to be released upon appropriate stimuli.

77. Endocytosis:-
•
• All eukaryotic cells are continuously ingesting
part of their plasma membrane. Endocytotic vesicles
are formed when segments of plasma membrane
invaginates enclosing a minute volume of
extracellular fluid (ECF) and its contents. The vesicle
then pinches off as the fusion of plasma membranes
seal the neck of the vesicle at the original site of in
vagination.
• Factors required are
– energy - usually derived from ATP hydrolysis,
– Ca++
– Contractile element in the cell probable the
microfilament system

78. Entry of material into
the nucleus through
endocytosis. The
phagosome travels
from the cell
membrane to the
nucleus, and then is
engulfed by the
nucleus, releasing its
contents

79. • Types:-
• 1) Phagocytosis
• 2) Pinocytosis
– Fluid phase pinocytosis
– Receptor mediated
• 1) Phagocytosis:-
• (Greek Word – Phagein – to eat) is the engulfment
of large particles like viruses, bacteria, cells or debris
by macrophages and granulocytes. They extend
pseudopodia and surround the particles to form
phagosomes which later fuse with lysosomes to
form phagolysosomes in which the particles are
digested. Biochemical mechanism is called
respiratory burst

80. Respiratory burst
• Respiratory burst (sometimes called oxidative burst) is
the rapid release of reactive oxygen species
(superoxide radical and hydrogen peroxide) from
different types of cells
• Usually it denotes the release of these chemicals from
immune cells, e.g., neutrophils and monocytes, as they
come into contact with different bacteria or fungi..
NADPH oxidase, an enzyme family in the vasculature
(in particular, in vascular disease), produces
superoxide, which spontaneously recombines with
other molecules to produce reactive free radicals.

81. • Respiratory burst plays an important role in the
immune system. It is a crucial reaction that occurs in
phagocytes to degrade internalized particles and
bacteria.
• To combat infections, immune cells use NADPH oxidase
to reduce O2 to oxygen free radical and then H2O2.
Neutrophils and monocytes utilize myeloperoxidase to
further combine H2O2 with Cl- to produce hypochlorite,
which plays a role in destroying bacteria. Absence of
NADPH oxidase will prevent the formation of reactive
oxygen species and will result in chronic granulomatous
disease

82. 82

83. • 2) Pinocytosis:-
• It is a property of all cells and leads to the cellular uptake
of fluids and fluid contents.
• (a) Fluid phase pinocytosis:-
• It is a non selective process in which uptake of a solute by
formation of small vesicles is simply proportionate to its
concentration in the surrounding extracellular fluid (ECF)
• (b) Receptors mediated absorptive pinocytosis:-
• The selective or absorptive pinocytosis is receptor
mediated ,LDL is good example ,LDL binds to LDL receptor
and complex is later internalized .,the cytoplasmic site of
these vesicles are coated with filaments mainly composed
of clathrin , these are called as clathrin coated pits .After
the LDL receptor complex is internalized the receptor
molecule are released back to cell surface but the LDL is
degraded by lysosomal enzymes .

85. • Clinical aspects: of receptor mediated
endocytosis with viruses are responsible for
many diseases like
Hepatitis virus affecting liver cells
Polio virus effecting motor neurons
AIDS effecting ‘’T’’ cells
Iron toxicity occurs due to excessive uptake by
endocytosis

86. Active Transport:-
• Active Transport is the transport of ions or
molecules across biological membrane, against
concentration gradient. Such transport requires
a transmembrane protein or carrier called
transporter and the energy derived from the
hydrolysis of ATP.
• Direct active Transport:-
• Some transporters bind ATP directly and use the
energy of its hydrolysis to drive active transport
they are called direct active transporters.

87. • Direct active Transport:-
– Na+/K+ AT Pase
– H+/K+ AT Pase
– Ca2+ ATpase of skeletal muscle
• Active transport results in solutes movement
against a concentration gradient or
electrochemical gradient and need energy.
• It is of two type
1. Primary active transport
2. Secondary active transport

88. PRIMARY ACTIVE TRANSPORT
• In primary active transport, the solute transportation is
coupled directly to the use of energy, from ATP.`
• The energy released by hydrolysis of ATP drives the solute
movement against an electrochemical gradient
Example:
• Sodium-potassium pump
• Primary active transport of Calcium (out side to inside)
• Primary active transport of Hydrogen ions in gastric gland and
renal tubules (distal and collecting tubules) The enzyme
hydrogen potassium ATPase (H+/K+ ATPase) is unique to the
parietal cells and transports the H+ against a concentration
gradient of about 3 million to 1, which is the steepest ion
gradient formed in the human body.

89. The H+/K+ ATPase
• H+/K+ ATPase is the proton pump of the stomach
and, as such, is the enzyme primarily responsible
for the acidification of the stomach contents
• The H+/K+ ATPase transports one hydrogen ion
(H+) from the cytoplasm of the parietal cell in
exchange for one potassium ion (K+) retrieved
from the gastric lumen. As an ion pump the H+/K+
ATPase is able to transport ions against a
concentration gradient using energy derived from
the hydrolysis of ATP

90. Na+ K+ ACTIVE COTRANSPORT
• The concentration of Na+ is lower in the cell than
outside, while K+ concentration is higher within the
cell
• This imbalance is established and maintained by a
primary active transport system in the plasma
membrane. The enzyme ‘Na+ K+ ATPase’ couples
breakdown of ATP to simultaneous movement of
both Na+ and K+ against their electrochemical
gradient

92. • For each molecule of ATP converted to ADP, the
transporter moves two K+ ions inward and three Na+
ions outward across the membrane
• The Na+ K+ ATPase is an integral protein which is
inhibited by
• Digitalis is a drug used to treat congestive cardiac
failure. It inhibits Na+ efflux leading to higher
concentration of Na+ in cells. This activates Na+ Ca+
co-transporter in cardiac muscle, which increases
influx of Ca+ , thus strengthening cardiac contractions

93. ATP-DRIVEN Ca2+ PUMPS
• The cytosolic concentration of Ca+ is slightly lower
than surrounding medium. Calcium ions are pumped
out of the cytosol by a ATPase,
The plasma membrane Ca+ pump
• It is an integral protein. The transporter binds Ca+ on
the side of membrane where its conc is low and
releases it on the side where its conc is high. The
energy released by ATP hydrolysis drives Ca+ across
the membrane against a large electrochemical
gradient

94. SECONDARY ACTIVE TRANSPORT
• Secondary active transport occurs when uphill
transport of one solute is coupled to the downhill
flow of a different solute that was originally pumped
uphill by primary active transport
• A gradient of an ion e.g. Na+ has been established by
primary active transport. Now movement of Na+ ion
down its electrochemical gradient then provides
energy to drive co-transport of a second solute
against its concentration gradient

96. • Transport system can be describe in a functional
sense according to
Num of mol moved and the direction of the
movement.
Or Whether movement is toward or away from
equilibrium. So they are a two types.
• UNIPORT
• Transport system that carry only one substrate
(e.g. glucose transporters) are called ‘Uniport
systems’ e.g Glucose out from the intestinal
mucosal cell to blood.

97. • CO-TRANSPORT
1. When the two solutes or ions move in opposite directions, the
process is ‘Antiport’ (Counter transport) In antiport two species
of ion or other solutes are pumped in opposite directions
across a membrane. One of these species is allowed to flow
from high to low concentration which yields the entropic
energy to drive the transport of the other solute from a low
concentration region to a high one. An example is the sodium-
calcium exchanger or antiporter, which allows three sodium
ions into the cell to transport one calcium out
2. When the two solutes move in the same directions, the process
is ‘Symport’ example is the glucose symporter SGLT1, which co-
transports one glucose (or galactose) molecule into the cell for
every two sodium ions it imports into the cell. This symporter is
located in the small intestines, trachea, heart, brain, testis, and
prostate.

99. Examples of Inherited Diseases of Ion Channels
• An increasing number of human diseases have
been identified as inherited mutations in
genes encoding ion-channels proteins. Some
examples are as follows.
• 1. Chloride-channel Diseases
• 2. Potassium-channel Diseases
• 3. Sodium-channel Diseases

100. • 1. Chloride-channel Diseases:
• Cystic Fibrosis.
• Inherited tendency for renal stones formation is caused
by a different kind of chloride channel than one involved
in cystic fibrosis.
• 2. Potassium-channel Diseases:
• Some inherited life-threatening defects in the heartbeat.
• A rare, inherited tendency to epileptic seizures in the
newborn.
• Several types of inherited deafness.
• 3. Sodium-channel Diseases:
• Inherited tendency to certain types of muscle spasms.
• Liddle’s syndrome. characterized by early, and frequently
severe, hypertension , Inadequate sodium excretion
through the kidneys because of a mutant sodium
channel.