the presetation ppt is useful for medical students of MBBS , BDS , and for Paramedics

1. The Cell Structure and Function
By
Dr: Muhammad Muqeem Mangi
MBBS, MPhil. Physiology
Associate Professor
Suleman Roshan Medical College
Tando Adam

2. OBECTIVES
• STUDENTS SHOULD LEARNT THE BASIC STRUCTURE
AND FUCTIONS OF CELL BY OBSERVING THESE
SLIDES
• AND ALSO UBDERSTAND THE BASIC FUNCTIONS OF
CELL ORGANELLS
• STUDENTS CAN DISTINGUESH DIFFERENT
STRUCTURE EASILY OF CELL
• THEY MAY UNDERSTAND THE BASIC CELL THEORY.
• AND LEARN THE DISEASES OF ORGANELLS

3. Organization of the Cell
• Water: 70% to 85%
• Ions: Na:(ecf) 142 (icf) 10, Cl:103-04, K:04-140, Ca:2.4-0.0001
• Proteins: 10% to 20%
• Lipids: 02%
• Carbohydrates: 01%
icf= extra cullular fluid icf= intracellular fluid
The cells are basic building blocks of the
body, forms tissues , organs , converting
nutrients into energy and perform its
functions , having hereditary code that
controls coping of themselves and
processes required substances by cell.
There are 100 trillion cells in human
being.
That can survive for months or years.
Provide appropriate nutrition's to its
surrounding fluid.
The different
substances that
makes the cell are
collectively called
Protoplasm

4. Robert Hooke -An English Mathematician & Physicist.
Robert Hooke, in 1665 took a piece of cork of Spanish Oak and prepared
thin slices which was then observed under a microscope.
Honey – Comb structure was observed with a number of box-live
compartments, each having a pore & separated from others by
diaphragms.
He called these compartments Cellulae (singular- cellula), now known as
Cells
(Latin – cella, meaning hollow space or compartments).
1. The CELL THEORY All organisms are composed of one or more cells.
2. Cells are the basic unit of structure and function in organisms.
3. All cells come from other cells.

5. Eukaryotic cells contain well cellular organelles
such as:
Nucleus
Mitochondria
Endoplasmic reticulum
Golgi apparatus
Peroxisomes
lysosomes
Cell Organells

6. i. Also called cell membrane / plasma lemma / bio membrane.
ii. Quasifluid (acts partially like fluid and partially like solid),
elastic, pliable & film-like thin partitions over and inside
cytoplasm.
iii.Average is 75 A(50-100A).
iv.Selectively permeable for solutes but semi permeable for
water.
v. Dynamic in nature. Any injured part of Membrane is repaired
within no time.
vi.Appear trilaminar or tripartite under electron microscope.
• Composition:-
a) Lipids (20-79%)
b) Proteins (20-70%)
c) Carbohydrates (1-5%)
d) Water (20%)
Plasma Membrane
i. Also called cell membrane / plasma lemma / bio membrane.
ii. Quasifluid (acts partially like fluid and partially like solid), elastic, pliable & film-
like thin partitions over and inside cytoplasm.
iii. Average is 75 A(50-100A).
iv. Selectively permeable for solutes but semi permeable for water.
v. Dynamic in nature. Any injured part of Membrane is repaired within no time.
vi. Appear trilaminar or tripartite under electron microscope.
Composition:-
a) Lipids (20-79%)
b) Proteins (20-70%)
c) Carbohydrates (1-5%)
d) Water (20%)

7. . Lipids
• Phosphoglycerides or phospholipids.
• Lipid molecules are amphiatic or amphipathic
i.e: they posses both hydrophilic & non polar
hydrophobic ends.
• Hydrophilic region is the head & hydrophobic part
contains 2 tails of fatty acids.
• Hydrophobic tail usually occur towards the centre
of members resulting in formation of a lipid bilayer

9. • They can be fibrous or globular, structural, carrier,
receptor or enzymatic.
• These also posses both polar & non polar side
chains.
• Polar hydrophilic linkages are towards outer side.
• Non polar hydrophobic linkages are either kept
folded inside or used to established connections
with hydrophobic part of lipids.
Proteins

11. Carbohydrates
• These are branched
or unbranched
oligosaccharides
• e.g.-
hexose,fucose,
hexoamine,
sialic acid etc.

12. FLUID – MOSAIC MODEL
1. The plasma membrane has 2 layers (a bilayer) of phospholipids (fats
with phosphorus attached) which at body temperature is like
vegetable oil.
2. Membrane is not solid but Quasifluid.
3. Protein molecules occur at places both inside ( intrinsic, integral
proteins) and on outer side of lipid bilayer (extrinsic, peripheral
protein )
4. Protein icebergs in a sea of lipids.
5. Integral proteins pass into lipid bilayer & establish hydrophobic bonds
with lipid molecules. Some run through out the lipid bilayer called
tunnel protein or transmembrane proteins.
6. These tunnels from channels for passage of water and water soluble
substance which passes selective properties for passage of different
ions.

13. 8. The extrinsic proteins are located more so on cytosolic face than on external face ( e.g.
spectrin)
9. Extrinsic proteins are attached covalently to phospholipid head or non-covalently to
transmembrane protein.
10. Proteins provide structural & functional specificity to
membranes
11. Proteins may shift laterally hence providing flexibility & dynamism to
membrane.
12. Proteins may function as enzymes, permeases, carriers.
13. Some lipids & extrinsic proteins present on outer side possess small carbohydrate molecule to
form glycolipids & glycoproteins. They constitute glycocalyx or cellcoat.
14. Conjugated oligosaccharides function as :-
a) Recognition centres.
b) Sites of attachments.
c) Antigens.
d) Provide negative charge to outer surface.
FLUID – MOSAIC MODEL

14. FLUID – MOSAIC MODEL

15. 1.Compartmentalisation.
2.Protection from injury
3.Providing organic connections between adjacent
cells (plasmodesmata & gap junctions)
4.Providing selective permeability barrier.
5.Transporting solutes.
6.Responding to external stimuli.
7.Energy transduction.
8.Secretory, excretory & waste products thrown out by
exocytosis.
FUNCTIONS OF CELL MEMBRANE

16. • In electron micrographs of cells, mitochondria
appears as – rods, spheres or filamentous bodies.
• Size: 0.5µm -1µm in diameter
up to 7µm in length.
MITOCHONDRIA

17. Cont: Mitochondria
• Mitochondria has got an inner
membrane and an outer membrane.
The space between these two is
called intermembranous space.
• Inner membrane convolutes into
cristae and this increases its surface
area.
• Both the membranes have different
appearance and biochemical
functions:

18. • Inner membrane:
• It surrounds the matrix.
• It contains components of electron transport system.
• It is impermeable to most ions including H, Na, ATP,
GTP, CTP etc and to large molecules.
• For the transport special carriers are present e.g.
adenine nucleotide carrier(ATP –ADPtransport).
• Complex II i.e. Succinate dehydrogenase .
• Complex Vi.e. ATP synthase complex.
Cont: Mitochondria

20. • Outer membrane:
•It is permeable to most ions and molecules
which can move from the cytosol to
intermembranous space.
• Matrix:
• It is enclosed by the inner mitochondrial
membrane.
• Contains enzymes of citric acid cycle.
Cont: Mitochondria

21. • Enzymes of β-oxidation of fatty acids.
• Enzymes of amino acids oxidation.
• Some enzymes of urea and heme synthesis.
• NAD
• FAD
• ADP,Pi.
• Mitochondrial DNA.
• Mitochondrial cytochrome P450 system- it
causes:
Cont: Mitochondria

22. a. Hydroxylation of cholesterol to steroid
hormones (placenta, adrenal cortex, ovaries
and testes)
b. Bile acid synthesis (liver)
c. Vitamin D formation( kidney).
Cont: Mitochondria

23. • Mitochondria plays a key role in aging-
•Cytochrome c component of ETC plays a main
role in cell death and apoptosis.
• have a role in its own replication- they contain
copies of circular DNA called mitochondrial
DNA, this DNA have information for 13
mitochondrial proteins and some RNAs.
• This is DNA inherited from mothers.
Cont: Mitochondria

24. • Most mitochondrial proteins are derived from
genes in nuclear DNA.
• Mutation rate in mt DNA is 10timesmore.
• Mitochondrial Diseases:
i. Fatal infantile mitochondrial myopathy and
renal dysfunction
ii.MELAS(mitochondrial encephalopathy, lactic
acidosis and stroke).
iii. Lebers hereditary optic neuropathy
iv.Alzheimer’s disease, Parkinson’s ,
Cardiomyopathies and diabetes.
Cont: Mitochondria

26. ENDOPLASMIC RETICULUM
 Discovered by Porter & Thompson (1945).
 Its a 3-D, complicated & inter
connected system of membrane–lined channels
running through cytoplasm, called Cisterns.(Flat
interconnected sac-like).
 Smooth E.R.: Ribosomes absent.
• Agranular E.R.
 Rough E.R. Ribosomes
present.
Granular E.R.

28. Rough Endoplasmic Reticulum
Rough Endoplasmic Reticulum• Rough Endoplasmic Reticulum
• These membranes enclose a lumen.
• In this lumen newly synthesized
proteins are modified.
• Rough appearance is due to the presence
of ribosomes attached on its cytosolic
side(outer side).
• These ribosomes are involved in the
biosynthesis of proteins.

29. Rough and Smooth
ENDOPLASMIC RETICULUM

30. CONTI:(R) ENDOPLASMIC RETICULUM
• These proteins are either incorporated into
the membranes or into the organelles.
• Special proteins are present that are called
CHAPERONES. Theses proteins play a role in
proper folding of proteins.
• Protein glycosylation also occurs in ER i.e. the
carbohydrates are attached to the newly
synthesized proteins.

32. • Smooth endoplasmic reticulum is involved in
lipid synthesis.
• Cholesterol synthesis
• Steroid hormones synthesis.
• Detoxification of endogenous and
exogenous substances.
• The enzyme system involved in detoxification is
called Microsomal Cytochrome P450
monooxygenase system(xenobiotic metabolism).
Smooth Endoplasmic Reticulum

33. CONT (S) ENDOPLASMIC RETICULUM
• ER along with Golgi apparatus is involved inthe
synthesis of other organelles –lysosomes &
Peroxisomes.
Elongation of fatty acids e.g.
Palmitic acid 16C-
Stearic acid 18C.
Desaturation of fatty acids.
Omega oxidation of fatty acids.

34.  Made up of smooth membrane saccules or cisternae, a
• network of tubules with vesicles and vacuoles.
 First seen by George in 1867 but named after Camillo
Golgi who in 1898 recognized its reticular structure.
• Functions
• Secretion - All glandular cells depend upon Golgi
complex for concentrating & packaging their products
inside a soluble protein coat.
 Formation of glycoproteins & glycolipids.
 Formation of sialic acid and galactose.
 Fat transport.
 Mediation of hormones produced by endocrine glands.
 Formations of lysosomes & secretory vesicles.
GOLGI COMPLEX (APPARATUS)

36.  Small vesicles bounded by a single membrane
containing hydrolytic enzymes in form of minute
crystalline or semi crystalline granules of 5-8
nm.
 Are called suicide bags.
 Work in acidic pH (pH=5)
 Formed by Golgi complex.
LYSOSOMES

38. CONT: LYSOSOMES
 Intracellular Digestion :- food obtained via
• phagocytosis is digested by Lysosomes.
 Extracellular digestion by release of enzymes
via exocytosis.
 Defence- lysosomes of leucocytes devour
foreign proteins, bacteria & toxic substances.
• Autophagy:- In metamorphosis of many animals,
certain embryonic parts are digested for growth of
other parts.
• Autolysis:-
 Formation of Thyroxine- active hormone thyroxin
in thyroid is formed through hydrolysis of
thyroglobulin by lysosomes.

41. CONT: LYSOSOMES
• In some genetic disease individual lysosomal
enzymes are missing and this lead to the
accumulation of that particular substance.
• Such lysosomes gets enlarged and they interfere
the normal function of the cell.
• Such diseases are called lysosomal storage
diseases
• Most impt is I-cell disease.

42. PEROXISOMES
• Called Peroxisomes because of their ability
to produce or utilizeH2O2.
• They are small, oval or spherical in shape.
• They have a fine network of tubulesin
their matrix.
• About 50 enzymes have been identified.
• number of enzymes fluctuates
according to the function of the cells.

43. CONT: OF PEROXISOMES
• Xenobiotics leads to the proliferationof
Peroxisomes in the liver.
• Have an important role in the breakdown of
lipids, particularly long chain fatty acids.
• Synthesis of glycerolipids.
• Synthesis of glycerol ether lipids.
• Synthesis of isoprenoids.
• Synthesis of bile.

44. CONT: OF PEROXISOMES
• Oxidation of D- amino acids.
• Oxidation of Uric acid to allantoin (animals)
• Oxidation of Hydroxy acids which leads to the
formationof H2O2.
• Contain catalase enzyme, which causes the
breakdown of H2O2.

45. CONT: OF PEROXISOMES
• Diseases associated:
•Most important disease is Zellweger
Syndrome. There is absence of functional
peroxisomes. This leads to the accumulation of
long chain fatty acids in thebrain, decreased
formation of plasmalogens, and defects of bile
acid formation.

46. NUCLEUS
 A specialized double membrane bound
protoplasmic body containing all the genetic
information for controlling cellular metabolism &
transmission to the posterity.
 Its the largest cell organelle.
 Found in the region of maximum metabolic
• activity. Commonly situated in the geometric centre
of cell .
 Spherical or oval in shape.

48. Nuclear Envelope:
• a.Nuclear Envelope:-
• separates nucleus from cytoplasm.
• Made up of lipoprotein & trilaminar membrane.
• Has pores or perforations which control passage of
substances to inside or outside of nucleus.
• b.Nucleoplasm
• its transparent semifluid & colloidal
• substances filling the nucleus.
• Contains nucleosides & enzymes.
• c. Nuclear matrix
• A network of fine fibrils of acid proteins functioning as
scaffold for chromatin.

50. • d. Chromatin
• Hereditary DNA - protein fibrillar complex.
• e. Nucleolus :-
• Naked, round or slightly irregular structure
attached to chromatin at the NOR (nuclear
organiser region).
• Has 4 components :-
I. Amorphous matrix.
II. Granular portion (proteins & RNA,2:1)
III.Fibrillar portion (nucleonema)
IV.Chromatin portion.
• Principal site for development of ribosomal

52. • I.Chromatin:-
• Hereditary material.
• Bear genes.
• Contains genetic information required for
growth & development.
II. Nucleus controls cell metabolism.
III.Formation of ribosomes in nucleolus.
IV.Directs cell differentiation.
V.Replication of nucleus essential for cell
replication.
CONT: OF NUCLEUS

54. • Chromosomes Rod shaped or thread-like
condensed chromatin fibres which are hereditary
vehicles as they store & transmit coded hereditary
information.
• There are 2 chromosome halves or chromatids
attached to each other by CENTROMERE.
• Chromosomes are of 4 types (based on
position of centromere) :-
(a)Telocentric – (centromere terminal at area of
telomere)
(b) Acrocentric – Centromere inner to telomere.
(c) Submetacentric – Centromere submedian
(d) Metacentric – Centromere median.
• Chromosomes contain a coiled filament called
• Chromonema.

55. CONT: OF CHROMOSOMES
Contains genes. All hereditary information
located in genes.
 Control synthesis of structural proteins thus
helping in cell division & cell growth.
 Control cellular differentiation.
 Can replicate themselves or produce their carbon
copies for passage to daughter cells & next
generation.
 Produce nucleoli for synthesis of ribosomes.

57. CONT: OF CHROMOSOMES
 Form a link between offspring & parents.
 Determine the sex of individual.
 By process of crossing over, they introduce
variations.
 Mutations are produced due to change in gene
Chemistry.

59. • Extremely minute, fibrous & tubular structures
which form the structural frame-work inside cell.
• 3 main types of protein filaments:-
i. Microfilament.
ii. Intermediate filaments.
iii. Microtubules.
• Function:-
a. Maintain the integrity of cells.
b. Cause Cyclosis.
c. Responsible for change in plasma membrane
during endocytosis & exocytosis.
CYTOSKELETON

62. • Ameboid Movement
a. Mechanism of ameboid
locomotion
b. Control of movement
c. Types of cells involved
• Cilia and Ciliary Movements

63. • R Orban’s – “ histology and embryology”,11th edition.
• GUYTON and HALL 13th Edition
• Gangnon review PHYSIOLOGY
• Robbins and Cotran’s Pathologic Basis of Disease, 8th
edition.
• Santos A. Susin; Daugas, E; Ravagnan, L; Samejima, K;
Zamzami, N; Loeffler, M; Costantini, P; Ferri, KF et al.
(2000).
• Two Distinct Pathways Leading to Nuclear Apoptosis".
Journal of Experimental Medicine 192 (4): 571–80.
doi:10.1084/jem.192.4.571. PMC 2193229. PMID 10952727
REFERENCES

64. Thankyou