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