Lec 3-Biochemical composition of cells.pptx

Biochemical composition of cell

Modern Cell theory-
• Cells make up all living matter.
• All cells arise from other cells.
• Chemical reactions of cell, anabolism and catabolism
take place inside the cell.
Thus, cell is the fundamental unit of life.

Types of cells
 Prokaryotic - lack a well defined nucleus or
membrane-bound organelles
 Example - Bacteria.
 Eukaryotic - have a well defined nucleus and
membrane-bound organelles.
 Example - Fungi, Plants, Animals.

Prokaryotic cells
Lacks a membrane
bound nucleus
Circular DNA , no histones
Few internal structures
Has a cell membrane
(cell wall)
Has ribosomes

Eukaryotic Cell
• Membrane bound Nucleus.
• Contains Cell Organelles.
• Linear DNA, Histones
• Unicellular to multicellular
.

Prokaryote Cell Eukaryote Cell
99. Cytoskeleton – absent
Ex- bacteria
1. Size – small 1- 10 μm
2. Unicellular
3. No nucleus
4. Circular DNA
5. No Histones.
6. No cell organelles
7. Ribosomes – free in
cytoplasm with size
50S +30S {70S}
8. Cell division – Binary fission
1. Large- 10 – 100μm
2. Uni/Multicellular
3. Nucleus –well defined.
4. Linear DNA.
5. Histones protein present
6. Membrane bound
Organelles.
7. Ribosomes – on the
surface of E.R. with size 60S
+40S {80S}
8. By mitosis.
9. Present.
Ex- fungi,plants,animals

Nucleus – control centre
 Prominent organelle.
 Most cells have a single nucleus. Mature RBCs have none.
skeletal muscle cells have multiple nuclei.
 Nuclear envelope – 2 membranes
 outer – in continuity with E.R.
 inner Peri nuclear membrane , with nuclear pores.
 Nuclear pores - consists of a circular arrangement of proteins
surrounding a large central opening
 Control movement of proteins and RNA across envelope.

Nucleus – Information centre
 Contains DNA – chromatin.
 Nucleolus - dense body.
 Ribosome Synthesis and r-RNA processing.
 Nucleoplasm- Sticky material that support
chromatin material.
 enzymes .ex-DNA Polymerase.
 Site for DNA Replication and RNA synthesis.

Details of the nucleus
Rough endoplasmic
reticulum
Nucleolus
Chromatin Polyribosome
Functions
1. Contains DNA.
2. Directs cellular activities.
3. Produces ribosomes in nucleoli.
Nuclear
envelope
Nuclear pore
Nuclear
pore
The nuclear envelope

Mitochondria
Elongated or rod shaped.
Powerhouse of Cell.
Number of mitochondria
varies depending on the activity
of the cell.

2 membranes-
Outer – continuous
Lipid in nature.
Selectively permeable (allows movements
of specific molecules)
Inner – protein in nature .
 High content (20%) of Cardiolipin.
impermeable.
folds to form cristae.( ↑ surface area )
 Inter-membrane space – adenylate kinase

Matrix- has specific Circular DNA , ribosomes and
enzymes.
Mitochondrial DNA –maternally inherited.
Functions –
Site of energy production – E.T.C.
Site of metabolic pathways.- TCA cycle, Urea Cycle,
F.A Oxidation etc.
Chloroplasts- in plant cells.
-Convert light energy into ATP by Photosynthesis.

Outer mitochondrial
membrane
Inner mitochondrial
membrane
Matrix
Cristae
Ribosome
Enzymes
Function
Generate ATP through oxidative
phosphorylation.
Helps in Biochemical reactions. Such as
oxidation of fatty acids, TCA, etc
Mitochondria

 Sites of protein synthesis.
 Made up of
 Protein
 rRNA
Present free in cytoplasm in prokaryotes
or attached to RER in eykaryotes.
consists of two subunits.
- large subunit
- small subunit.
 Prokaryotes- 70S-> 50S +30S
Eukaryotes- 80S-60S + 40S

interconnected network of
tubules– cisternae
 Extend from nucleus to
plasma membrane .
 Two types
-Rough ER
-Smooth ER

 RER- synthesizes proteins.
 SER- synthesizes phospholipids, cholesterol (in many tissue)
& steroid hormones (adrenals, gonads).
 In liver & Kidney - Detoxifies drugs, toxins &
Carcinogens.
 SER - site of Glycogen metabolism.
 Removes the phosphate group from G-6-P; and release
free glucose in blood.
 Sarcoplasmic reticulum - Stores & releases Calcium ions in
the cells (that trigger contraction in muscle cells.)

 Consists of 3 to 20 cisternae,
small, flattened membranous sacs.
Prominent in cells that secrete
proteins
 SORTING UNIT- Modifies,
sorts, packages, & transport
proteins from RERE

Small Membrane-bounded vesicles
present in cytoplasm
SUICIDAL BAGS .
60 kinds of powerful digestive and
hydrolytic enzymes.
They break down excess or
worn-out cell parts.
They may be used to destroy
invading viruses and bacteria.
Lysosomes

A peroxisome is a membrane-bound organelle
(formerly known as a microbody), found in the cytoplasm
of virtually all eukaryotic cells.
Contain several oxidases. – Peroxidase Also
known as Catalase
Functions :-
 Oxidation of amino acids.
 oxidation of long chain fatty acids.
 Protects cell from the toxic effects of H2O2.
 Dysfunction of Peroxisomes leads to Zellweger syndrome

Fluid content of cell.
Cytoplasm is a thick solution that fills each
cell and is enclosed by the cell membrane.
It is mainly composed of water, salts, and
proteins.
Site for many metabolic pathways.
ex- Glycolysis, fatty acid synthesis, purine
synthesis.

A network of protein filaments that extends throughout the
cytoplasm.
 anchored to plasma membrane.
Three types of filamentous proteins -
Microtubules
Intermediate filaments
Microfilaments
Provides shape to cell. Acts as internal framework.
 Helps in uptake of materials into cell.
Helps in internal movement of cell organelles , movement of
cells and muscle contraction.
Helps in Cell division.

 Long, Hollow, unbranched cylinders.
 made up of protein “tubulin”,
FUNCTIONS:
 Microtubuleshelpin structural support and maintainthe
shapeofthe cell.
 Helps inmovementoforganelles,secretoryvesiclesetc.
 Formationand function ofmitotic spindlesohelpincelldivision
 Movementofciliaandflagella.

INTERMEDIATE FILAMENTS
Polymers of long rod like proteins.
These filaments are thicker than microfilaments but thinner
than microtubules.
Made up of – Keratin,Desmin etc.
FUNCTIONS:
Provide mechanical support to the cell.
Help in intercellular attachment.

Thinnest elements of the cytoskeleton.
Composed of the protein actin
 Form a meshwork under plasma membrane
Functions :-
Mechanical support for the cells.
Example – Microvilli is rich in microfilaments
involved in muscle contraction, cell division,
and cell locomotion.

Mitochondria-ATP production , metabolic pathways
Nucleus-contains genetic material
Ribosome- proteins formation
Endoplasmic Reticulum-protein translation, folding
Golgi Apparatus-modification, sorting and
transport of proteins.
Transport network- E.R ,Golgi.
Vacuole-Storage, secretory
Lysosomes -digestion, cell death
Peroxisome – breaks toxic substances.

 Selectively permeable barrier that surrounds the cytoplasm of a
cell.
 Lipid bilayer – Davson & Danielle.
 Is described by the fluid mosaic model- Singer and Nicolson.
 Made up of 3 macromolecules………
 Lipids
 Proteins
 Carbohydrates.

Integral (transmembrane)
proteins
Cholesterol
Glycolipid:
Carbohydrate
Lipid
Glycoprotein:
Carbohydrate
Protein
Extracellular
fluid
Channel protein
Phospho
Lipid
bilayer
Cytosol

 75% - Phospholipids
 20% - Cholesterol
 5% - Glycolipids.
( polar & nonpolar)
 Most of them are - Amphipathic
 Acts as Permeability barriers.
Membrane Lipids

Head
Tail
“Head” – Polar part – phosphate group
“Tail” – Non polar part – long chain fatty acids
include……
Glycero, Sphingo P.L –
phosphptidylcholine,
phosphptidylinositol,
plasmalogens &
sphingomyelin.
Phospholipids
Phosphate gr.
fatty acid

Cholesterol –
 weakly amphipathic
 interspersed among other lipids in both layers of the
membrane.
 Stability to membrane .
 alters Fluidity of membrane.
Fatty Acids-
 unsaturated cis fatty acids - ↑ fluidity.
Glycolipids -
 present only on the outer surface of membrane.

Membrane Proteins -
 Two types of proteins are present in membrane -
Integral proteins
Peripheral proteins
 Integral proteins - partially / totally immersed in it.
 Most integral proteins are transmembrane proteins- extend
through out the lipid bilayer.
 Most of them are glycoproteins.
 Peripheral proteins - bind loosely with the polar heads of
membrane lipids at the inner or outer surface of the membrane.

Functions
Transmembrane proteins –
Ion channels
Carriers (transporters)
Peripheral proteins –
Receptors
Enzymes

Membrane Carbohydrates
 covalently bound to lipids and proteins to form glycolipids and
glycoproteins.
 These are mostly - Glucose , Galactose , Mannose
 Proteoglycans- outer surface.
 Glycocalyx – loose CHO layer on outer surface of cell .
Functions –
 helps in inter-cellular attachment .

Special features –
 Fluid mosaic model – in a sea of lipid bilayer ,
proteins float
 Asymmetric – outer and inner face of membrane
have different components.
 Anchored to Cytoskeleton .

Functions of cell membrane
 Acts as a semi-permeable barrier.
 Associated with several enzymes.
Contain receptors for hormones.
Contain recognition sites for antibodies.

Transport across Cell membrane
support
 Essential to maintain equilibrium of cell
Certain substances must move into the cell to
metabolic reactions.
 Other substances produced by the cell for export
or as cellular waste products must move out of the cell.

Transport across Cell membrane
 Uniport
 Cotransport
Mechanisms –
Passive transport.
 Simple diffusion
 Facilitated diffusion
Active transport.
 Primary Active Transport
 Secondary Active Transport
Bulk Transport [MACROMOLECULES]
 Exocytosis.
 Endocytosis.

 Uniport- Transport of single type of molecule in one direction. E.g.
transport of glucose in RBC by GLUT.
 Cotransport-
 Symport – Transport of molecules in same direction.
ex- Na- glucose transporter.
 Antiport - Transport of molecule in opposite direction. E.g.
chloride-bicarbonate exchanger.
Uniport Antiport

Passive Transport
Simple Diffusion :-
Movement of particles from the area of higher conc. to an
area of lower conc. (i.e., along the conc. gradient).
It does not require energy and carrier proteins.
Ex. – Transport of -
 gases
 lipid soluble molecules

Facilitated diffusion
Movement of molecule from higher to lower
concentration with the help of transporter proteins.
Transporter Protein Diffusion of molecules through
membrane.
 Protein in nature.
 selective .
 Moves from high conc. to low conc.

Facilitated diffusion-
downtheconc. gradient
requirescarrierprotein.-carrier-mediateddiffusion
doesnotrequireenergy.
morerapidthansimple diffusion.
Dependson no. of carrier proteins.
worksasping-pongmechanism.
 uniportmechanisms
Ex.- transport ofGlucosebyGLUT,
aminoacids .

Osmosis.
 The diffusion of water through a semipermeable membrane.
Movement of water molecules occur from an area of lower
solute concentration to an area of higher solute
concentration.
 Clinical Significance-
 Decreased formation of urine in hypovolemic conditions.
 Edema due to high salt concentration.
 Tonicity and its effects on red blood cells (RBCs).

Active Transport.
 Transport against conc. Gradient .
 carrier mediated.
 requires energy.
 used directly from hydrolysis of ATP .
 Ex. – sodium-potassium pump,
- calcium pump / ca+2- ATP ase .

Endocytosis
 Engulfing large molecules by the cell.
 Two type of endocytosis.
 Phagocytosis-cell eating
ingestion of large molecules, such as bacteria into the cell.
- occurs only in specialised cells
ex- WBC – engulf bacteria
 Pinocytosis- cell drinking
Uptake of fluid / fluid contents into thecell.
- occurs in all cells.
ex- Uptake of proteins into cell

Exocytosis
Expulsing molecules out from the cell.
Fate of molecule released by exocytosis may be……..
Peripheral proteins
Part of extracellular matrix
Released to extracellular medium

Lec 3-Biochemical composition of cells.pptx

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