Chapter 5

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Biological Sciences
David Harrison

Chapter 5 – Cell Biology ‘Mitochondria’ - Anaerobes – organisms that captured and utilized energy by means of oxygen independent (anaerobic) metabolism. I.e. Glycolysis and fermentation. - 2.7 billion years ago Cyanobactera – carried out photosynthetic process - Over time, species evolved that were protected from damaging effects of molecular oxygen, and possessed metabolic pathways that utilized the molecule to great advantage. - Incorporated oxygen into metabolism so could completely oxidize such compounds to CO2 an d H2O - Organisms became dependent on oxygen are aerobes - Eukaryotes used oxygen as means of energy extraction takes placed in mitochondrion - Mitochondria have evolved from ancient aerobic bacterium that took up residence inside cytoplasm of anaerobic host cell 5.1 Mitochondrial Structure and Function - Mitochondria are large enough to be seen in light microscope - Can be sausage shaped or highly branched tubular network - Occupy 15 to 20 percent of volume of liver cell - Primary suppliers of ATP - There two membranes outer and inner mitochondrial membranes - Out membrane completely encloses the mitochondrion (outer boundary) - Interior of organelle contains series of double layered membranous sheets or cristae that meet up with inner mitochondrial membrane at the boundary of the organelle - Role as energy transducers is intimately tied to membranes of cristae - Cristae contain large amount of membrane surface needed for aerobic respiration and ATP formation - Inner boundary membrane and internal cristal membranes are functionally distinct, although they are joined by narrow connections - Membrane divides into two aqueous compartments o Interior of the mitochondrion called matrix o Between outer and inner membrane called intermembrane space - Matrix has gel like consistency in presence of high concentration of water soluble proteins - Intermembrane space proteins initiate cell suicide Mitochondrial Membranes - Outer membrane is 50 percent lipid and contains mixture of enzymes - Inner membrane contains more than 100 different polypeptides and has high protein lipid ratio (75 percent protein/25 percent lipid) - Inner membrane is devoid of cholesterol and rich in unusual phospholipids - Outer mitochondrial membrane is homologous to an outer membrane - Outer mitochondrial membrane contain porins, integral proteins that have large internal channel surrounded by barerel of beta strands - Inner mitochondrial membrane is highly impermeable - All require special me
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