* Introduction:-> Mitochondria are double membrane bound cell organelle found in almost all eukaryotes.
-> They are known as "POWER HOUSE OF THE CELL" because they generate energy in the form of ATP through cellular respiration. -> It was discovered by Albert von kolliker in 1857 and was named mitochondria by Carl Benda in 1898.
-> It can clearly observed with an electron microscope by Palade in 1952.
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* Introduction:
-> Mitochondria are double membrane bound cell organelle found in almost all eukaryotes.
-> They are known as "POWER HOUSE OF THE CELL" because they generate energy in the form of ATP through cellular respiration.
-> It was discovered by Albert von kolliker in 1857 and was named mitochondria by Carl Benda in 1898.
-> It can clearly observed with an electron microscope by Palade in 1952.
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* GENERAL FEATURES OF MITOCHONDRIA:
1) SHAPE: Oval or rod shape .
2) SIZE: About 0.5 to 1.0 micrometer in diameter and upto 10cm long.
3) NUMBER PER CELL: Varies with energy need (they are few in number in resting cells , thousands in number in active cell (E.g. Muscle and liver cells) .
4) COLOUR: They are colourless or semi - transparent .
5) PRESENCE: Only present in eukaryotes and absent in prokaryotes.
* ORIGIN OF MITOCHONDRIA:
-> Mitochondria arise by growth and divisioning pre existing mitochondria .[ I.e. self replication].
-> According to Endosymbiotic theory mitochondria originates from free living aerobic bacteria that enters the ancestral cells and form a symbiotic relationship.
* STRUCTURE OF MITOCHONDRIA:
-> Mitochondria is surrounded by two membranes and has four main parts :
1) OUTER MEMBRANE:
A) It is a smooth and continuous membrane .
B) It contains porein proteins making it permeable to the small molecules and ions.
C) It acts as a protective layer .
D) Also helps in exchange of materials with in cytoplasm.
2) INNER MEMBRANE:
A) It is highly folded into finger like projections , called Cristae it folds increases surface area for enzymes .
B) It contains enzyme for electron transport chain (ETC) and ATP synthase.
C) The membrane is selectively permeable , allow passage of specific ions and molecules .
3) INTER MEMBRANE SPACE:
A) It is a narrow space between outer membrane and inner membrane .
B) It is rich in enzymes like Adenylate kinase that help transfer energy molecules ( ATP/ADP) .
4) MATRIX:
A) It is the inner space enclosed by the inner membrane .
B) It consists of mitochondrial DNA ( mt DNA ) - circular , double standard , ribosomes (70 s type) for protein synthesis , enzymes for kerb's cycle ( TCA CYCLE) and t-RNA , ATP , ions and metabolites .
* FUNCTIONS OF MITOCHONDRIA:
1) ENERGY PRODUCTION( ATP Synthesis) :
-> Mitochondria perform aerobic respiration ( oxidation of glucose , fatty acids and amino acids).
-> The energy released is stored as ATP (Adenosine Triphosphate) .
# MAIN STEPS FOR ENERGY PRODUCTION:
-> Glycolysis in cytoplasm to produce pyruvate .
-> Kreb's cycle / TCA cycle in matrix .
-> Electron transport chain in inner membrane.
-> OXIDATIVE PHOSPHORYLATION - produce ATP by ATP synthase enzyme .
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)
2) SELF REPLICATION:
-> Mitochondria contains its own DNA , RNA and ribosomes .
-> They can replicate independently like the cell of bacteria .
3) REGULATION OF CELLULAR MECHANISM:
-> It provides intermediates for fatty acids , amino acids and steroid synthesis .
4) CALCIUM IONS STORAGE:
-> Helps in storage and regulation of calcium ions within the cell.
5) ROLE IN APOPTOSIS:( Program cell death)
-> It is a natural process.
-> Release of cytochrome-c from mitochondria activates cascades leading to controlled cell death.
6) THERMOGENESIS: (Heat production)
-> In adipose tissue specially in infants (new borns) mitochondria generates heat instead of ATP through uncoupling proteins.
7) ROLE IN AGEING AND DISEASE:
-> Damage to mitochondrial DNA can lead to ageing and neuromuscular diseases.
E.g: Parkinson's disease
Alzeihmer's disease.
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