Download MBBS Physiology Presentations 69 The Cell Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st Year, 2nd Year, 3rd Year and Final year Physiology 69 The Cell PPT-Powerpoint Presentations and lecture notes




THE CELL

Though chemical analysis of living things is

possible, because of its complex organization and

interaction of molecules Life in the form of living

cell can not be produced

Cell is the smallest living entity which serves living

building blocks for the immensely complicated

whole body.

THE CELL

Life in the form of living cell can not be produced
Cell theory ? relation between cell and life

? Cell is the smallest structural & functional

unit. Can carry out living processes

? Functional activities related to the specific

structural property

? Living building blocks of animal or plant

? Organism's structure and function depends

upon characteristics of its cells

? All new life & new cells are formed from

preexisting cell

? Cells of one organism are fundamentally

similar in structure & function

Observation of cell
?Cannot be seen by naked eye ? smallest visible

particle is 5-10 times larger than typical cell
?Seen by microscope ? middle of 17th century
?Better vision of cells in tissues with `soapy mixture'

of fluid inside ? early 19th century
?Electron microscopy ? internal structure of cell ?

1940
?Recently,- powerful microscopes, biochemical

techniques, cell culture technology, genetic

engineering
Overview of Cell structure ?Total trillion cells

- 200 different cell types

3 Subdivisions

Plasma membrane Nucleus

Cytoplasm

Encloses

Contain cells

Portion of

the cell

genetic

cell interior

material

not occupied

by nucleus
Plasma membrane ?
?thin membranous structure enclosing each cell
?Oily barrier bet. ECF & ICF
?Holds contents of cell
?Gated wall ? selective movement of mol. Bet

ICF & ECF

Nucleus ?
- Largest, single, organized compartment

- Spherical or oval, near the centre
- surrounded by double layered

nuclear membrane having nuclear pores
allowing traffic between nucleus and
cytoplasm
- Genetic material in nucleus ? DNA
Functions of nucleus

directs synthesis of proteins

- serves as genetic

blue print during cell

Structural and enzymes

duplication

controlling chemical reactions

- Continue

DNA provides

identical type of

`instructions' through

cell line within the

3types of RNA

body and in

reproductive cell

Messenger Ribosomal Transfer to transfer genetic

RNA

RNA

RNA

material to next

generation

Cytosol

Cytoplasm

Organelles

Complex gel

Site for compatible

like liquid

chemical reactions

I Cytosol

elaborate protein -gives shape

network

-Provides internal

(cytoskeleton)

organization
-Regulates its

movements
II Organelles

distinct,
highly organized,
membrane enclosed,
occupies about ? of total

cell volume

Each organelle

`Speciality shops' in cell
Separate compartment
Separate contents

6 main types of organelles- similar in all cells

v Endoplasmic

reticulum

- contain specific set

of chemicals

v Rough ER

required for

v Smooth ER

particular cellular

function

v Golgi complex

- can carryout

v Lysosomes

incompatible

v Peroxysomes

chemical reactions

simultaneously

v Mitochondria

v Vaults
Endoplasmic reticulum -- protein and lipid
manufacturing factory.

Elaborate, fluid filled

extensively distributed,

membranous system

SER

RER

2 types continuous with each other and their

relative amount varies with the function of

cell

SER ? network of tiny interconnected tubules

RER ? project outwards from SER as stacks of
flattened sacks
- outer surface of membrane studded
with ribosomes ? rough granular appearance

New protein on ribosomal RNA

Released in ER lumen

Exterior as

Construction of

hormones or

new cell

enzymes

membrane or

organelles

Synthesis of lipids by enzymes present in the

membrane released to lumen with protein

pressed attachment of carbohydrate buds off as

transport vesicle

Smooth ER -No ribosome, so not involved in

protein synthesis,
- serve as a central packaging &

discharge site for molecules which are

to be transported from ER
-formation of Transport vesicles which

contain new protein and lipid and is

membrane bound and passes to Golgi

complex , formation of peroxisomes
- Membrane used is replaced by newly

formed protein & lipid
Additional responsibilities in different cells

1) Steroid secreting cells have abundant SER

2) Liver cells ? membrane of SER contain

enzymes involved in detoxification

3) In muscle cells SER stores Ca++ which

plays imp. role in process of muscle

contraction

Golgi Complex Stacks of flattened, curved,

membrane bound sacs or cisterns
-may not be physically connected

with each other
-thin at the center and dilated at

the periphery
- Number varies ?cells

specialized in pr. synthesis may

have 100s of sacs
Mechanism of function

Transport vesicles containing Cargo from SER

fuses with the inner most sac of Golgi complex

material travel through the layers of sacs to the

outer sacs in the form of transport vesicles
During transit
1) raw material final finished product
2) sorting and directing the finished products
a) secretion to exterior of cell
b) construction of new plasma membrane

c) incorporated in other organelles e.g. lysosomes

Secretory vesicles
Membrane with

specific proteins

Recognition Coat proteins Docking

marker for

for curling of marker on

cargo on inner membrane

outer side

surface

inside coat

protein ?

Cargo ? conc. finished product with

v-SNARE

appropriate a.a. sequence acting as

sorting signal
Exocytosis

Budding off vesicles in cytosol seperating

specialized finished products from cytosol .

Movement towards membrane on appropriate signals

Attachment with special pr. marker on target

membrane ? t SNARE

Fusion of membrane

Opening of vesicle

Release of secretion

Peculiarities of secretary process

1) Once pr. is synthesized does come in

contact with cytosol
2) Synthesis and storage are well ahead

of time of requirement
3)Diffferent secretory vesicles for

different destination
Lysosomes

?Membrane enclosed sacs containing powerful

hydrolytic enzymes
?Average number ? 300 per cell
?No fixed structure- vary in size and shape
?0.2 ? 0.5 m in diameter
?Granular when inactive
?Membrane protects rest of the cell
?Membrane and enzymes from Golgi complex

Extracellular material to be tackled by

lysosome is brought into the cell by

endocytosis

3 types

pinocytosis

phagocytosis

Specialised

All cells

Receptor

cells

mediated

endocytosis
A.Pinocytosis - Cell drinking nonselective
B. continuous process seen in all

?Me ce

m lls

brane deforming protein attached to membrane

?Formation of pouch by dipping of membrane
?Sealing of ends
?Endocytic vesicle with ECF
?Vesicle is pinched off by protein Dynamin
?ECF to the cell and loss of extra plasma membrane

added during exocytosis

Pinocytosis

ECF

ECF

dynamin

Membrane deforming

coat protein

Endocytic

vesicle
B. Receptor mediated endocytosis ? highly

selective process to import imp. specific large

molecules. Requires energy & Ca++

Coated pit Cathrin, actin,

myosin

C. Phagocytosis

? Internalization of large

multimolecular particles by

specialized cells e.g. certain

types of w.b.c.s ( Professional

phagocytes)
bactebactium

Pseudopodia

internalization

Phagoso-

some

Fusion

Residual

body

absorption

digestion

Phagocytosis

Autophagy ?
Role in regression of organ ? uterus, mammary glands
Removal of aged or damaged organelles
Rupture of lysosomal membrane CAUSES SELF

DESTRUCTION but minimal damage because

optimum pH for hydrolytic enzymes is acidic.
Damage to nuclear DNA alters genetic properties

Deficiency of one or more enzymes lead to

storage disease e.g. TAY SACHS disease-
Peroxisomes

?Several hundreds
?? to 1/3 size of lysosomes
?Transport of H+ across membrane so acidic pH
?Membrane enclosed sacs with powerful oxidizing

enzymes which use O2 to remove hydrogen from

organic molecules and detoxify wastes produced in the

cell or foreign toxic compound by formation of H2O2

which is oxidant but accumulation is prevented by

catalase which is antioxidant
?H2O2 H2O + O2

Mitochondria

Outer membrane

Electron

transport

Inner membrane

protein

Crista

Matrix

Intermembrane space

Dissolved enzymes for citric

acid cycle

Chemiosmotic

reactions
?100s-1000s in single cell

?Energy organelle or power plant

?Extract energy from nutrient and transfer in to

usable form

?Number and location in cell varies

?Round shaped or oval

?Possess their own DNA which produces molecules

required for generating energy

?Defect in DNA lead to degenerative diseases or

ageing

?Double membrane ? outer smooth, inner folded

forming cristae



Energy release from the nutrients and its storage

Dietary food

Energy in carbon bonds

digestion

Smaller absorbable molecules

Through cell

In the cell through membrane
1 mol. Of glucose

2 pyruvic acid

2 ATP

Cytosol

mol.

+

Anaerobic glycolysis

2Acetyl co A

Matrix

Citric acid cycle 4NADH+2FADH2

2 ATP

+

Cristae

Low energy

-

Electron transport

O

compounds

2 + e

+

-

+ electron

H+ e

Intermembrane space

Chemiosmotic reaction ADP + Pi

32 ATP

Synthesis of ATP- Oxidative phosphorylation
? Release of energy during electron transport

reactions used for active uptake of H+ by inner

membrane
? Accumulation of H+ in intermembrane space
? Transport of H+ through channels in inner

membrane
? Activation of ATP sythetase attached to

channel protein
? ADP + Pi ATP (32mol) with utilization of

O2 from atm.
Chemiosmotic reactions

H+ H+ H+ H+ H+ H+ H+ H+

H+ H+ H+

H+

ATP

synthetase

ADP + Pi

ATP

Uses of ATP

1. Synthesis of new chemical compounds for

secretion and growth

2. Membrane transport

3. Mechanical work
Vaults

? 3 times larger than ribosomes
? Octagonal barrels with hollow interior
? Not seen with ordinary stain
? Pass through nuclear pore
? transporting messenger RNA and other material
across nuclear membrane
? May be responsible for multi drug resistance in
cancer cells.

Cytosol

? Semi liquid surrounding organelles
? Highly organized gel like mass with different
composition at diff. sites
? Cytoskeleton is dispersed through out
? enzymes regulating intermediary reactions
? Ribosomal protein synthesis (used for cell)
? Storage of fats, glycogen ( Inclusions),
secretory vesicles
Cytoskeleton

Complex protein network portion of cytosol which

act as `bones and muscles ` of the cell.giving shape ,

support and control their movements

3 elements

Microtubules microfilament intermediate filaments

Microtubules

Largest skeletal element, slender, long

hollow unbranched tubes

Functions

A) Maintains asymmetric cell shape e.g.

B) axon

B) Transport of secretary vesicles and

other materials in any direction by

use of motor protein and energy



? Movement of specialized cell

projection such as cilia, flagellum

Tubulin

subunit ? Distribution of chromosomes during

mitosis of spindles
Microfilament

- Smallest element of cytoskeleton
- Actin is present in most cells
- 2 strands of globular actin

Actin - Role in the cell -

subunit Cellular contractile system

Mechanical stiffener for
cellular projection-microvilli

Intermediate filaments
Tough, maintain structure integrity of cell and

resist mechanical stress
e.g. microfilaments in axon
Keratin in skin cells
Functional systems of cells

I. Ingestion
II. Digestion of foreign substances
III.Synthesis and formation of new

structures

IV.Energy extraction
V. Locomotion ? ameboid movement,
VI. ciliary movement

This post was last modified on 08 April 2022