subcellular organelles-par t1

8/13/2019 subcellular organelles-par t1

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Cell Structure

& Function


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Cell Theory

All living things are made up of cells.

Cells are the smallest working units of all

living things.

All cells come from preexisting cells

through cell division.


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Definition of CellThe cell is the structural and

functional unit of life.

A cell is the smallest unit that is

capable of performing lifefunctions.


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Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria


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Two Types of Cells

Prokaryotic

Eukaryotic


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Prokaryotic

Smaller in size 1-10m

Rigid cell wall

Do not have membranebound organelles

Few internal structure

Anaerobic / aerobic

Eg: Bacteria


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Eukaryotic

Larger in size 10-100 m Contains membrane and membrane bound organelles

(little organs) .

Plant Animal


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PROKARYOTIC EUKARYOTIC

SIZE 1-10m 10-100 mTYPE UNICELLULAR MULTICELLULAR

OUTER COVERING RIGID CELL WALL LIPID BILAYER WITH

PROTEINS

CYTOSKELETON ABSENT PRESENT

MEMBRANE BOUND

ORGANELLES

NO EVOLVED

RIBOSOMES FREE IN CYTOPLASM STUDDED ON ER

GOLGI APPARATUS STORAGE GRANULES FLATTENED MEMBRANE

LYSOSOMES ABSENT VESICLE CONTAININGHYDROLYTICENZYMES

CELL DIVISION FISSION MITOSIS


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Cells are surrounded by cell membrane

The interior of the cell is divided:1. Nucleus

2. Cytoplasm

The Cytoplasm contains two components

1. Cell organelles

2. Cytosol


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Cell Parts


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Cell Membrane

Function of cell membrane

1. Seperates the cell from

external environment.

2. Selective permeability.

3. Link adjacent cells together

4. Exocytosis and endocytosis.


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The Cell Membrane Structure

(Fluid mosaic model)


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Phospholipids

Fatty acid

Phosphate

Fatty acid tails

hydrophobic

Phosphate group head

hydrophilic

Arranged as a bilayer


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Phospholipid bilayer

polarhydrophilic

heads

nonpolarhydrophobic

tails

polarhydrophilic

heads


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More than lipids In 1972, S.J. Singer & G. Nicolson proposed that membrane

proteins are inserted into the phospholipid bilayer.

Two types of membrane protein

1. Integral membrane

2. Peripheral membrane


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Membrane Proteins

Proteins determine membranes specific functions cell membrane & organelle membranes each have

unique collections of proteins

Membrane proteins: peripheral proteins

loosely bound to surface of membrane

integral proteins penetrate lipid bilayer, usually across whole membrane

transmembraneprotein


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Proteinsdomainsanchormolecule

Within membrane

nonpolaramino acids hydrophobic

anchors proteininto membrane

On outer surfaces of

membrane polaramino acids hydrophilic

extend into extracellular

fluid & into cytosol

Polar areasof protein

Nonpolar areas of protein


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Membrane carbohydrates

Play a key role in cell-cell recognition ability of a cell to distinguish one cell from

another

important in organ &

tissue development


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Membrane Junctions

Some cell not anchored to other cells butsuspend in the fluid.

Most cells are packaged into tissues and

are not free to move. Many cells physically joined by

specialized types:

1. Desmosomes2. Tight junctions

3. Gap junctions


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Inside the Cell


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Nucleus

Almost all cells contain a single nucleus.

Directs cell activities

Separated from cytoplasm by nuclear membrane

Function-Stores and transmits genetic information in theform of DNA. Genetic information passes from the

nucleus to the cytoplasm


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Nuclear Membrane

Double membrane structure.

Separates nucleus from the

cytosol.

Inner membraneperinuclearmembrane

Outer memebrane continuous

with rough ER

NUCLEAR PORE COMPLEX:Controls movement of proteins

and ribo nucleic acid (RNA)

across nuclear envelope


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Chromosomes

DNA is coiled into a

dense mass Chromatin.

Contain instructions for

traits & characteristics

http://library.thinkquest.org/12413/structures.html


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Nucleolus

Site of RNA processing and ribosome synthesis.


E d l i R ti l


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Endoplasmic Reticulum

Moves materials around in

cell.

Smooth type (Agranular):lacks ribosomes. Site of lipid

molecule synthesized.

Rough type (Granular):

ribosomes embedded in

surface. Packaging of

proteins to be secreted or

distributed.

Network of interconnect ing membranes enclosing

channels/c isternae that are con t inuous from per inuclear

envelope to outer plasma memb rane


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PEROXISOME

Small organellesmicrobodies

formed by budding from smooth er

Carries out oxidation reaction.

Toxic H2O2broken down by catalase

Oxidation of fatty acids can also occur

in peroxisomes.


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Ribosomes

Composed of proteins

and several RNA

molecules

Proteins synthesisingmachinery of the cell

Either bound to the

organelle or found

free in the cytoplasm



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Golgi Apparatus

Italian biologist CamilloGolgi discovered thesestructures in the late1890s.

Also called dictyosomes.

Curved flattened fluid

filled sacs.

Unique protein sortingdevice (packaging &

secretion). http://library.thinkquest.org/12413/structures.html


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On the proximal or cis concave side, golgi complex receives newly

synthesized protein from rough ER as vesicles.

Postranslational modification takes place in the golgi lumen lipid

precursors are added

Distal transside releases modified proteins through secretory vesicles

These fuse with the plasma membrane and the contents expelled

exocytosis


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Lysosome

(organel les w ith packet o f enzyme)

Involved in intracellulardigestion

Suicidal bag of cell

Ph lower than cytosol(ph=5)

Lysosomal enzymes are

acid hydrolases-digestion

of carbohydrates,proteins, lipids and

nucleic acid


Si ifi f l


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Significance of lysosomes:

Death of the cell

Disintegration of lysosomal bodies

Release of lysosomal enzymes

Autolysis of the cell

Gout- urate crystals depositon

around the kenee joints.

Phagocytosis of these crystals

Damage to vacuoles &

release of enzymes

I cell disease: lysosomes lack enzymes

MITOCHONDRIA


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MITOCHONDRIAPOWER HOUSE OF THE CELL

A spherical rod like structure

OUTER MITOCHONDRIAL MEMBRANEConsists of phospholipids and cholesterol.

Contains the protein porin.

Forms channels. Substances < 10,000 m.w.

Diffuses freely

INNER MITOCHONDRIAL MEMBRANE

Rich in proteins- high proportion of cardiolipin

impermeable to polar and ionic substances

enters only through specific transport proteins

CRISTAE:

folded inner mitochondrial membrane

Inter memb rane space:


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Inter memb rane space:

Space between outer and inner membrane

Mitochond rial matr ix :

Region enclosed by inner membrane

Site of TCA cycle, fatty acid oxidation

Matrix contains several strands of DNAenzymes, ribosomes for protein synthesis


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Function:

1. Houses enzymes of TCA cycle, fatty acid

oxidation, electron transport chain, oxidative

phosphorylation- generation of ATP.

2. Steroidogenesisusing cyt P450

3. Part of urea cycle and heme synthesis.

CYTOSKELETON


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CYTOSKELETON

Complex array of subcellular organelles dispersed throughout

the cell.

Major components are:

1. Microtubules: role in the assembly and disassembly of the

spindle structures during mitosis.

2. Microfilaments: slender cylinder like structures made up of

contractile protein actin3. Microtrabeculae - fragile tubes forms a trasient network in

the cytosol

Maintain shape of cell

Produces cellular and subcellular movementsCYTOPLASM (CYTOSOL)

Soluble material of cytoplasm

site of many metabolic reactions


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LYSOSOMES ACID PHOSPHATASE HYDROLASES

PLASMA

MEMBRANE

Na+, K+ ATPASE

5' NUCLEOTIDASE

TRANSPORT OF MOLS

IN AND OUT OF CELLS.

INTERCELLULAR

ADHESION AND

COMMUNICATION

GOLGI

APPARATUS

(DICTYOSOMES)

GALACTOSYL

TRANSFERASE

INTRACELLULAR

MODIFICATION OF

PROTEINS.

GLYCOSYLATIONSULFATION

REACTION.


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PEROXISOME CATALASE / URIC

ACID OXIDASE

DEGENERATION OF

FATTY ACID AND

AMINO ACID.

PRODUCTION ANDDEGENERATION OF

H2O2.

CYTOSKELETON NO SPECIAL ENZYME

MARKERS

MICROFILAMENTS,

MICROTUBULES

CYTOSOL LDH ENZYME OF

GLYCOLYSIS, FATTY

ACID SYNTHESIS.

NUCLEOULUS RNA POLYMERASE SITE OF SYNTHESIS

OF r RNA


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