Mitochondria

Angel Anna LalMsc Biotechnology1st year.

INTRODUCTION The mitochondrion (plural mitochond

ria) .[greek]; It is a double membrane-

bound organelle found eukaryotic cells.

mito= threadchondrion = granule like

Found in cytoplasm of the cell. Power house of cell.

First observed by Richard Altman (1894).

Term mitochondria was coined by Carl Benda (1898).

SIZE: Mitochondria range from 0.5 to 1.0 μm in diameter.

SHAPE: normally Sausage shaped,

In fibroblasts-elongated and thread like

NUMBER: Depends on type size and functional state of cell.Eg: An average liver cells contain around 1500 mitochondria.

LOCATION: Cells with high enrgy requirements;Eg:Sperm tail, Muscle, Flagella

In most animals ,

oozyte mitochondria [maternal] are the only

mitochondria that is inherited

.

Spermatazoa mitochondria [paternal] also

enters oocyte during fetilization,but destroyed

during early embryonic development.

Mechanism not yet ellucidated.

1. Outer Membrane

2. Intermembrane Space

3. Inner Membrane

4. Cristae

5. Matrix

OUTER MEMBRANE

Simple phospholipid bilayer.

It encloses the mitochondrion.

Containing protein structures called porins.

Ions, nutrient molecules, ATP, ADP, etc. can pass through the outer membrane

with ease.

INNER MEMBRANE

Is freely permeable only to oxygen, carbon dioxide, and water.

Contains complexes of the ETC, the ATP synthase complex, and transport

proteins.

Presence of sophisticated ion transporters exist.

Several antiport systems exist, allowing exchange of anions between

the cytosol and the mitochondrial matrix.

It is devoid of cholesterol and rich in phospholipid & cardiolipin.

Intermembrane space

Matrix

the space between inner membrane and outer membrane {O cavity}

It has high proton concentration.

The space between inner and outer memebrane is approx 70 angstrom.

Conc is same as that of the cytosol.

CRISTAEAre folds of inner mitochondrial membrane.

Stalked particles or inner membrane spheres: cristae is

covered with this inner membrane spheres called stalked

particles or knobs or heads.

They contain protein called F1 portion & F0 portion. For

ATP synthesis and ATO oxidation.

MITOCHONDRIAL MATRIX:

Gel like consistency

Dense ,homogenous

2/3rd of total protein of mitochondria

Mitochondria have: - enzymes

-ribosomes

-DNA

-mRNA

-granules

-fibrils

-tubules.

Major enzymes include enzymes involved in:

-Synthesis of nucleic acid and proteins

-Fatty acid oxidation

-TCA CYCLE (except succinate dehydrogenase)

MITOCHONDRIAL DNA (mt DNA):

Double stranded, covalently closed,

circular molecule.

Occurs in multiple copies.

Most usually remains attached to inner

mitochondrial membrane.

Stores biological info required for growth

and multiplication of mitochondria.

Can undergo replication and duplication.

Human mt DNA 2 rRNA

22 tRNA

Not absolutely autonomous depends on

nuclear DNA.[partially autonomous]

FUNCTIONS OF MITOCHONDRIA:

Energy transducer of the cell- synthesis of ATP

Kreb’s cycle in matrix

ETC system

Phosphorylating system- ATPase

Extra mitochondrial inheritance:

mtDNA contains plasma genes (extra chromosomal genes)

Transmitted from mother to the offspring

Synthesis of mtDNA, RNA, protein.

Bring about gene expression through gene duplication

transcription and translation.

Synthesis 13 different polypeptides in human.

Site of several metabolic reactions

Outer membrane

Oxidation of epinephrine

Degradation of tryptophan

Elongation of fattyacid

Inner membrane : oxidative phosphorylation

Matrix

Kreb’s cycle

Beta oxidation

Detoxification of ammonia in urea cycle

Storage of calcium ions

OTHER FUNCTIONS:

production of heat ( non shivering thermogenesis).

[ The unharnessed potential energy of proton-electrochemical

gradient produced during ETC is released as heat.]

Role in apoptosis ( programmed cell death).

Synthesis of estrogen and testosterone.

Role in neurotransmitter metabolism.

Role on cholesterol metabolism.