The document provides information about cells and cell organelles. It discusses the key components of cells, including the nucleus that houses DNA, mitochondria which generate energy, the endoplasmic reticulum that modifies proteins, Golgi apparatus that packages proteins, lysosomes for digestion, peroxisomes that break down hydrogen peroxide, and the plasma membrane that encloses the cell. It describes the structures and functions of these organelles and compares prokaryotic and eukaryotic cells. The document also discusses the fluid mosaic model of the cell membrane and its role in transport.

1. CELL
&
CELL ORGANELLES
Dr. AREEBA GHAYAS
TUTOR
DEPTT. OF BIOCHEMISTRY

2. CHEMICAL MOLECULES OF LIFE
 Life is composed of lifeless chemicals molecules.
 Mainly six elements:
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous, And Sulfur.
(90%) of the dry weight of the human body.
 A single cell of the bacterium E.coli contains about 6,000
different organic compounds.
 Human beings contains 1,00,000 different types of organic
compounds.

3. COMPLEX BIOMOLECULES
BIOMOLECULES BUILDING BLOCK MAJOR FUNCTIONS
1) Protein Amino acids Fundamental basis of
structure and function cell
2) DNA Deoxyribonucleotides Repository of hereditary
information
3) RNA Ribonucleotides Protein biosynthesis
4) Polysaccharide Glucose Storage form of energy to
meet short term demands

4. Chemical Composition of Man
Constituent Percent Weight(kg)
Water 61.6 40
Protein 17.0 11
Lipid 13.8 9
Carbohydrates 1.5 1
Minerals 6.1 4

5. The Cell
 The cell is the structural and functional unit of living
organisms; proposed by Schleiden & Schwann
 All animal tissues including human are also organized from
collections of cells. Thus cell is the fundamental unit of life.
 Modern cell theory can be divided into the following
fundamental statements:
1. All living things are made of cells.
2. Cells carry out the functions needed to support life.
3. Cells come only from other living cells.

6. TYPES OF CELLS
 The cells of the living kingdom may be divided into two
categories.
1) Prokaryotes: pro-before ,karyon- nucleus Ex: bacteria
2) Eukaryotes: Eu-true , karyon- nucleus Ex: animals and plants

7. COMPARISON BETWEEN
PROKARYOTIC & EUKARYOTIC CELLS
Characteristic Prokaryotic Cell Eukaryotic Cell
1) Size Small Large
2) Cell Membrane Cell Is Enveloped By A Rigid
Cell Wall
Flexible Plasma Membrane
3) Sub Cellular Absent Present
4) Nucleus No defined nucleus. DNA
present but not separated from
rest of the cell; Histone absent.
Present
5) Energy
Metabolism
Absent Present
6) Cell Division By binary division Mitosis
7) Cytoplasm Undifferentiated Contains various membrane
bound organelles ; such as
Mitochondria, Golgi bodies ,
Lysosomes & Peroxisomes

8. Cell has three major components:
1. Nucleus
2. Cytoplasm with its organelles
–– Mitochondria
–– Endoplasmic reticulum
–– Golgi apparatus
–– Lysosomes
–– Peroxisomes
3. Plasma membrane
(cell membrane)
THE CELL ORGANELLES

9. 1) NUCLEUS
1) Nucleus was first discovered by ROBERT BROWN
2) Nucleus is the control centre of the cell; it contains the DNA
organized into chromosomes which carry genetic information.
3) The nucleus is surrounded by a double membrane called
nuclear envelope.
4) The outer membrane is fused with the endoplasmic reticulum at
multiple sites.
5) Nuclear pores (multiprotein complexes) occur at points where
the outer and inner membranes are connected.

11.  DNA replication and RNA transcription of DNA occur in the
nucleus.
 The nucleolus is non-membranous and contains RNA polymerase,
RNAase, ATPase and other enzymes but no DNA polymerase.
 Nucleolus is the site of—
- Synthesis of ribosomal RNA (r-RNA).
-Assembling of ribosome subunits
FUNCTION OF NUCLEUS

12. 2) MITOCHONDRIA
1) They are spherical, oval or rod-like bodies.
2) Erythrocytes are an exception which derive their ATP from
glycolysis due to lack of mitochondria.
3) Mitochondria are the powerhouse of the cell, where energy
released from oxidation of food stuffs is trapped as chemical
energy in the form of ATP.

14. Structure Of Mitochondria
 The mitochondrion is bounded by two concentric membranes that
have different properties and biological functions.
Mitochondrial Membranes
(a) Outer mitochondrial membrane:
Consists mostly of phospholipids , cholesterol & protein (Porin).
(b) Inner mitochondrial membrane:
Are very rich in proteins. The inner membrane projects inwards
into folds that are called cristae .

15. (c) Intermembrane space:
is the space between the outer and inner membranes. The
outer membrane is freely permeable to small molecules, the
intermembrane space has about the same ionic composition as
the cytosol.
(d) Mitochondrial matrix: The region enclosed by the inner
membrane is known as the mitochondrial matrix.

17. Functions Of Mitochondria
The inter-membrane space contains several enzymes involved in
nucleotide metabolism.
 The gel-like matrix (mitosol) consists of enzymes required for the
metabolic pathways (Glycolysis) of oxidation of pyruvate
(pyruvate dehydrogenase).
 The mitochondrial matrix is the site of most of the reactions of the
citric acid cycle and fatty acid oxidation.

18.  Components of electron transport system and oxidative
phosphorylation that are responsible for the synthesis of ATP are
embedded in inner membrane.
 Mitochondria contain their own DNA, (mtDNA), which in human
encodes 13 respiratory chain proteins, small and large rRNAs and
enough tRNAs to translate all codons.
 Mitochondria have a key role in aging; cytochrome c,an initiator
of apoptosis.

19. MITOCHINDRIA-CLINICAL ASPECTS
 Mitochondrial DNA can be damaged by free radicals.
 Age related degenerative disorders –Parkinson’s disease,
cardiomyopathy.
 Mutational defects leading to Mitochondrial myopathies-
 Leber’s hereditary optic neuropathy (LHON)
 Mitochondrial encephalomyopathy, lactic acidosis and
stroke-like episodes (MELAS)
 Myoclonus epilepsy with ragged red fibers (MERRF)

20. 3) ENDOPLASMIC RETICULUM
 Eukaryotic cells are characterized by several membrane complexes
that are interconnected by separate organelles.
 These organelles are involved in protein synthesis, transport,
modification, storage and secretion.
 It is a network of interconnecting membranes enclosing channels
or cisternae, that are continuous from outer nuclear envelope to
outer plasma membrane.

21. TYPES OF ER
There are two kinds of endoplasmic reticulum (ER):
(i) Rough surfaced ER, They are coated with ribosomes. Near the nucleus, this
type of ER merges with the outer membrane of the nuclear envelope.
(ii) Smooth surfaced ER: They do not have attached ribosomes.

22. Functions of ER
(a) Function of rough ER:
Rough ER synthesises membrane lipids, and
secretory proteins. These proteins are inserted through
the ER membrane into the lumen of the cisternae where
they are modified and transported through the cell.
(b) Function of smooth ER:
Smooth endoplasmic reticulum is involved:
(i) In lipid synthesis
(ii) Modification and transport of proteins synthesised in the
rough ER.

23. ER STORAGE DISEASES
ERSD are defects in the secretory protein encoded by
mutated gene-
 Lipoprotein lipase deficiency
 Abetalipoproteinemia
 Disorders of lipid metabolism
 Growth hormone receptors deficiency
 Hereditary hypothyroidism

24. 4) GOLGI APPARATUS
 Camillo Golgi described the structure in 1898.
 The Golgi organelle is a network of flattened smooth
membranes and vesicles.
 In Golgi apparatus proteins are processed, modified and
prepared for export from the cell.
 It works in association with endoplasmic reticulum, where
proteins for certain destinations are synthesized.

25. FUNCTION
1. Golgi bodies are secretory cell organelles.
2. The modified proteins are sorted, packaged and
transported to destination inside or outside the cell. Golgi
apparatus plays the role of post office mail sorting room, the
mail in this case being newly synthesized proteins.
3. Post- translational modification of proteins occurs in golgi
lumen.
4. Golgi bodies & ER give rise to primary lysosomes &
peroxisomes.
5. Acrosome of sperm cell is derived from golgi bodies.

26. Golgi bodies-clinical aspects
 Wilson's disease
 Menkes disease
 Duchenne muscular dystrophy

27. 5) LYSOSOMES
 Lysosomes contain packet of enzymes.
 Lysosomes are digestive tract of the cell, they are involved in
digestion of proteins, lipids, carbohydrates and nucleic acids.
 The lysosomal enzymes have an optimum pH around 5.
These enzymes are
a. Polysaccharide hydrolysing enzymes
(alpha-glucosidase, alpha-fucosidase, beta-galactosidase, beta-
glucuronidase, hyaluronidase, lysozyme)
b. Protein hydrolysing enzymes
(cathepsins, collagenase, elastase, peptidases)
c. Nucleic acid hydrolysing enzymes (ribonuclease,
deoxyribonuclease)

29.  Lysosomal enzymes destroy the foreign substances and
pathogens like bacteria ,virus that are engulfed by the cells of
immune system.
 Destroys aging cell organelles that are no longer required by
the host cell.
 They are capable of self-destruction of the cell (autophagy).
 Lysosomes are also called ‘suicide bags’ and play an important
role in apoptosis
 After death, they play role in postmortem autolysis.
 During development, play an important role in the formation
of specialized tissues such as fingers and toes.
For example, lysosomes digest the webbed tissues that join
fingers and toes in the embryo.
FUNCTION

32. 6) PEROXISOMES
1) Peroxisomes ,also known as microbodies, are single
membrane cellular cell.
2) These vesicles are concerned with the metabolism of
hydrogen peroxide (H2O2),hence the name peroxisome.
3) They contain such enzymes that forms, uses and destroy the
H2O2.
4) The H2O2 produced in the cell are highly toxic & is
decomposed into H2O and oxygen by the enzyme Catalase
present in them.

33. FUNCTION OF PEROXISOME
 Contains Catalase which causes breakdown of H2O2.
 They are present in hepatic cells takes part in breakdown
(oxidation) of-
Long chain fatty acid
D-amino acid to ethanol
Uric acid to allantoin
 They also help in synthesis of glycolipids, plasmalogens,
isoprenoids & bile.

34. 7) CYTOSOL AND CYTOSKELETON
1) The cellular matrix is collectively referred to as cytosol.
2) The cytoplasmic filaments are of three types:
1) microtubules
2) micro filaments
3) intermediate filaments.
The cytoskeleton play a role in movement of cell organelles from
one position to other within the cell.

37.  The plasma membrane is an envelop surrounding the
cell.
 It separates and protect the cell from the external
environment.
 Plasma membrane also provide a connecting system
between the cell and its environment .
BIOLOGICAL MEMBRANES

38. Chemical Composition
 The membranes are composed of lipids, proteins, and
carbohydrates.
 The actual composition differs from tissue to tissue.
 Large globular protein molecules are interspreaded in
this lipid bilayer.

40. Structure Of Membranes
 A lipid bilayer model originally proposed for membrane
structure in 1935 by Danielle and Davson has been
modified.

41. FLUID MOSAIC MODEL
 The membrane is sometimes referred to as a fluid mosaic.
 The membrane mosaic is fluid because most of the interactions
among its components are non-covalent, leaving individual
lipid and protein molecules free to move laterally in the plane
of the membrane

43.  The lipid of the membrane provides a barrier that obstructs the
movements of water and water-soluble substances from one cell
compartment to another.
 The integral protein molecules in the membrane do penetrate all
the way through the membrane, organized into actual pores, for
passage of specific substances through the membrane.

44. The approximate composition of cell membrane is:
 Protein: 55%
 Phospholipids: 25%
 Cholesterol: 13%
 Other lipids: 4%
 Carbohydrate: 3%

45. Lipid of the membrane
 The basic lipid bilayer is composed of phospholipid
molecules.
 One end of each phospholipid molecule (head group) is
soluble in water that is it is hydrophilic, the phosphate
end.
 The other end (tail group) is soluble only in fats; that is,
it is hydrophobic, the free fatty acid end.

47. A and B: Structure of phospholipid.
(A) A common glycerophospholipid;
(B) Diagrammatic representation of phospholipid.
A B

48. The principle phospholipids in the membrane are:
 Glycerophospholipids:
• phosphatidylcholine,
• phosphatidylethanolamine, and
• phosphatidylserine
 Sphinogophospholipid: sphingomyelin.

49.  The lipid composition varies among different cell types,
with phosphatidylcholine being the major plasma
membrane phospholipid in most cell types.
 Plasma membrane for example, is enriched in
cholesterol and contains no detectable cardiolipin
(diphosphatidylglycerol lipid)
 Mitochondrial membrane is very low in cholesterol and
sphingolipids but that contain cardiolipin.

50. CHOLESTEROL
 The cholesterol molecules in the membrane are also lipid in
nature, interspreaded between the phospholipids & maintains
membrane fluidity
 The presence of cholesterol and the cis unsaturated fatty
acids in the membrane prevent the hydrophobic chains from
packing too closely together.
 Loss of membrane fluidity affect integral proteins, such as
ion channels and receptors for neurotransmitters involved
conducting the nerve impulse.

51.  Most of the membrane proteins are glycoproteins.
 Two types of membrane proteins:
1. Integral membrane proteins- protrudes all the way
through the membrane. They are very firmly associated
with the lipid bilayer.
2. Peripheral membrane proteins: attached either to
membrane surface or to integral proteins.; do not penetrate
through the membrane.
MEMBRANE PROTEINS

52.  They are associated with the membrane through electrostatic
interactions and hydrogen bonding with the hydrophilic domains
of integral proteins and with polar head groups of membrane lipids

53. Functions of Membrane Proteins
 Peripheral proteins function as enzymes or as controllers of transport of
substances through the cell membrane.
 Integral membrane proteins –
1. Function as channels (pores) through which water molecules and water
soluble substances, especially ions, can diffuse between extracellular
and intracellular fluids.
2. Act as carrier proteins transporting substances that could not penetrate
the lipid bilayer.
3. As receptors for hormones and neurotransmitter.
4. Role in cell signalling.

54. Membrane carbohydrates
 Membrane carbohydrates occur in combination with proteins or
lipids in the form of glycoproteins or glycolipids.
 Some of the proteins and lipids on the external surface of the
membrane contain short chains of carbohydrate
(oligosaccharides) that extent into the aqueous medium.

56.  proteoglycans are loosely attached to the outer surface of
the cell.
 the entire outside surface of the cell has often a loose
carbohydrate coat glycoproteins and glycolipids called the
glycocalyx.
 Carbohydrate constitutes 2% to 10% of the weight of cell
membrane.

57. Functions of Membrane carbohydrates
 Many of the carbohydrates have a negative electrical charge,
which gives most cells an overall negative surface charge that
repels other negative objects and restricts the uptake of
hydrophobic compounds.
 The glycocalyx of some cell attaches to the glycocalyx of other
cells, thus attaching cells to one another.
 act as hormone receptor such as insulin
 involved in immune reactions.

58. Marker Enzymes For Different Organelles
 The purity of isolated subcellular fraction is assessed
by the analysis of marker enzymes.
 Marker enzymes are the enzymes that are located
exclusively in a particular fraction, and thus become
characteristic of that fraction.

60. Thank you

61. MEMBRANE
TRANSPORT
Dr. AREEBA GHAYAS
TUTOR
DEPTT. OF BIOCHEMISTRY

62. MEMBRANE TRANSPORT
 Cell membranes form closed compartments around the
cytoplasm to define cell boundaries.
 The cell membrane has selective permeability.
 Selective membrane permeability is conferred by specific
transporters/carriers and channels.

63. TRANSPORT ACROSS MEMBRANES

65. PASSIVE TRANSPORT
 Transport is from higher concentration to lower
concentration.( Downhill transport)
 The substance pass through the membrane from both
sides.
 Transport does not require energy in the form of ATP.

66. TYPES OF PASSIVETRANSPORT
A. Simple Diffusion
B. Facilitated Diffusion
1) Channel mediated
2) Carrier mediated
C. Osmosis

68. A. Simple Diffusion
 It is a passive transport.
 From High concentration to low
concentration. (downhill transport).
 Kinetic energy used for the movement of
molecules.
 Small& unchargedmolecules likeO2, CO2,
salts , urea, ammonia & amino acids.
 No channel proteins or carrier proteins
required (movement through the bilayer).
 Diffusion stops when equilibrium is
achieved

70. 1) Solute moves along the concentration gradient from
higher to lower concentration (downhill transport).
2) No energy is required.
3) Occurs through the mediation of carrier or channel
proteins.(hence,2 types)
4) Sometimes regulated by hormones. E.g. GLUT4
regulated by insulin in muscle and adipose tissue.
5) Follows Saturation kinetics contrast from simple
diffusion.
ex: glucose, galactose, leucine, phenylalanine
B. FACILITATED DIFFUSION:

71.  A ping pong model is put forth to explain the occurrence
of facilitated diffusion.
Mechanism Of Facilitated Diffusion:

72. According to this mechanism, :-
 carrier / channel transport protein exists in two
conformation, in the ping conformation it is exposed to
the side with high solute concentration.
 This allow the binding of solute to specific sites on the
carrier protein.
 The protein changes in pong conformation , exposed to
the side with low solute concentration where the solute
molecule is released.

73. C. OSMOSIS
 Osmosis is the diffusion of
water across the semi
permeable membrane.
 The direction of osmosis
depends on the concentration
of solutes inside and outside
the cell.

76. OSMOTIC PRESSURE

77. ACTIVE TRANSPORT
 Active transport occurs against a
concentration gradient from low to high
concentration (uphill transport).
 Energy in the form of ATP is required.
 Carrier mediated process like facilitated
diffusion.
 Follows Saturation kinetics contrast from
simple diffusion.
 The most important primary Active
transport systems are ion pumps.

78. Types Of Active Transport

84.  Ouabain
 Digoxin
Clinical Aspect of Na-K ATP Pump

86. Examples of Symport

88. Co-transport system

90. VESICULAR TRANSPORT
 Occurs by fusion of formed vesicles or formation of new
vesicles.
 Macromolecules (such as sugars, amino acids, hormones,
neurotransmitters, cellular secretions, etc) cannot be
transported by diffusion or active transport process.
 Clathrin, coating proteins, dynamin & docking
proteins are the vesicular transport proteins used for
formation & transport of vesicles.

91. Types Of Vesicular Transport
1) Endocytosis: formation of vesicle from the cell
membrane (intake)
2) Exocytosis: fusion of vesicle from the cell membrane
(release)

93. 1) Endocytosis: Intake of macromolecules by the cells.
 Approximately 2% of the exterior surface of plasma
membrane possesses characteristic Coated-pits.
 The pits can be internalized to form coated vesicles
which contain an unusual protein called Clathrin.
 E.g., The uptake of LDL molecules by the cells.
 Occurs by constitutive pathway

94. Uptake Of LDL Molecules

95.  Endocytosis occurs when the plasma membrane is
pulled inwards and will form a “pocket” around a particular
substance.
 The substance will become
enclosed in the vesicle which
is then pinched off and begins
moving through the cytoplasm.
 Cells can bring in solids and
liquids using this process.

96. Types of endocytosis

98. 2. Exocytosis: Release of macromolecules from the cells to
outside.
1. In golgi bodies, Macromolecules are packaged into a
vesicle.
2. The vesicles in cytoplasm are transported to the
plasma membrane.
3. Vesicles fuses with plasma membrane
4. Contents of the vesicle are released into the external
environment of the cell.
 Role of exocytosis is to secrete substances being
produced or excrete waste products.
 The secretion of hormone occur by Exocytosis. e.g.
Insulin

100. Diseases due to loss of membrane
transport systems:
 Hartnups disease
 Cystinuria
 Rickets