Anaerobic glycolysis and mitochoondria

Anaerobic glycolysis is the sole source of energy for erythrocytes because these cells do not contain mitochondria Both the brain and gastrointestinal tract also produce much of their energy from glycolysis Under aerobic conditions pyruvate can be transported into the mitochondria and participate in the TCA cycle in which it becomes completely oxidized to CO2 and H2O Complete oxidation is accompanied by the release of relatively large amounts of energy much of which is captured in ATP molecules by the mechanism of oxidative phosphorylation

The glycolytic enzymes function within the cytosol of the cell But the enzymes catalyzing the TCA cycle reactions are located within the mitochondrion for complete oxidation Oxidative phosphorylation is the culmination of energy yielding metabolism in aerobic organisms All oxidative steps in the degradation of carbohydrates fats and amino acids converge at this final stage of cellular respiration in which the energy of oxidation drives the synthesis of ATP In eukaryotes oxidative phosphorylation occurs in mitochondria Each cell contains one to ten mitochondria dependent on the various cell types Mitochondria have two membranes The outer mitochondrial membrane is readily permeable to small molecules (Mr 5,000) and ions which move freely through transmembrane channels formed by a family of integral membrane proteins called porins The inner membrane is impermeable to most small molecules and ions including protons (H+) the only species that cross this membrane do so through specific transporters The inner membrane bears the components of the respiratory chain and the ATP synthase The mitochondrial matrix enclosed by the inner membrane contains the pyruvate dehydrogenase complex and the enzymes of the citric acid cycle the fatty acid beta-oxidation pathway and the pathways of amino acid oxidation all the pathways of fuel oxidation except glycolysis which takes place in the cytosol