Semi-autonomous nature of mitochondria
Mitochondria contain all requirements of protein synthesis.
2.DNA molecules(rich in G-C ratio) to form mRNA and also replicate.
ATP molecules to provide energy.
The mitochondria can form some of the required proteins but for most of proteins,these are depedent upon nuclear DNA and cytoplasmic ribosomes,so the mitochondria are called semi-autonomous organelles.
According to endosymboitic origin of mitochondria were intially a free living.aerobic bacteria which during to the process of evolution entered an anaerobic cell and become established as mitochondria.This theory is supported by many similarities which exist between bacteria and mitochondria.
Chemical composition of Mitochondria
Cohngave the chemical composition of mitochondria:
Protein=65%-70%; Lipids=25-30%(90%phospholipids and 10% cholestrol,Vit.E,etc); RNA=5-7%;Some amount of DNA 2-5%.
The mitochondria matrix has many catabolic enzymes like cytochrome oxidase and reductase, fatty acid oxidase ,transaminase,etc.
Enzymes of Mitochondria:
Monoamine oxidase,glycerophosphatase, acyltransferase ,phospholipase A.
Cytochrome b,c1,c,a (cyt.b,cyt.c1,cyt.c,cyt.a, cyt.a3) NADH,dehydrogenase, succinate, dehydrogenase,ubiquinone ,flavoprotein,ATPase.
Adenylate kinase,nucleoside diphosphokinase.
Pyruvate dehydrogenase, citrate synthase,aconitase, isocitrate dehydrogenase, fumerase, malate dehydrogenase, dehydrogenase.
Mitochondria are self-duplicating organelles due to presence of DNA molecules so new mitochondria are always formed by growth and division of pre-existing mitochondria by binary fission.
Function of Mitochondria:
1.Mitochondria are called power house or storage batteries or ATP mills formation of ATP is called oxidative phosphorylation.
2.Intermediate products of cell respiration are used in the formation of steroids,cytochromes, chlorophyll etc.
3.These are also seat of some amino acid biosynthesis.
4.Mitochondria also regulates th calcium ion concentration inside the cell.
5.Site of thermiogenesis.
6.Yolk nucleus(a mitochodrial cloud and golgi bodies) controls vitellogenesis.
7.Mitochodria of spermatid form nebenkern(middle piece) of sperm during spermiogenesis
8.Mitochondria release energy during respiration.
9.Mitochodria contain electron transport system.