Mitochondrial structure and its function

1. Mitochondria
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2. Introduction to mitochondria
• First observed by Richard Altman (1894).
• Mito means thread
• chondrion means granule like
• It is a double membrane bound organelle found eukaryotic
cells.
• Found in cytoplasm of the cell.
• Also known as power house of cell.
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3. Introduction to mitochondria
• Term mitochondria was coined by Carl Benda (1898).
• Mitochondria are responsible for the conversion of nutrients
into energy–yielding molecule ATP to fuel the cells activities.
• The function known as aerobic respiration is the reason
mitochondria are frequently referred to as the powerhouse of the cell.
• Mitochondria are derived from bacteria by a process termed as
endosymbiosis.
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4. Morphology
Size: Mitochondria range from 0.5 to 1.0 μm in diameter.
Shape: normally Sausage shaped.
Number: Depends on type size and functional state of cell. Like in liver cells around 1500
mitochondria are present.
Location: Cells with high energy requirements Eg:Sperm tail, Muscle, Flagella
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5. Structure
Mitochondrial structure consists of
• Outer Membrane
• Intermembrane Space
• Inner Membrane
• Cristae
• Matrix
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6. 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.
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7. 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.
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8. CRISTAE
• Are 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.
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9. MITOCHONDRIAL MATRIX
• Gel like consistency
• Dense ,homogenous
• 2/3rd of total protein of mitochondria
Mitochondria have
• Ribosomes
• DNA
• mRNA
• Granules
• Fibrils
• tubules
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10. MITOCHONDRIAL MATRIX
Major enzymes include enzymes involved in
• Synthesis of nucleic acid and proteins
• Fatty acid oxidation
• TCA CYCLE (except succinate dehydrogenase)
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11. 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
• Not absolutely autonomous depends on
nuclear DNA.[partially autonomous]
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12. FUNCTIONS OF MITOCHONDRIA
• Energy transducer of the cell- synthesis of ATP
Krebs'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.
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13. Sites of several metabolic reactions
Outer membrane
• Oxidation of epinephrin
• Degradation of tryptophan
• Elongation of fatty acid
Inner membrane
• Oxidative phosphorylation
Matrix
• Krebs cycle
• Beta oxidation
• Ammonia detoxification
• Calcium ion storage
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14. 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.
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