The Krebs Cycle Occurs in the matrix of the mitochondrion Aerobic phase (requires oxygen) 2-carbon acetyl CoA joins with a 4- carbon compound to form a 6- carbon compound called Citric acid

Citric acid (6C) is gradually converted back to the 4-carbon compound -ready to start the cycle once more The carbons removed are released as CO 2 -enzymes controlling this process called decarboxylases The hydrogens, which are removed, join with NAD to form NADH2 -enzymes controlling the release of hydrogen are called dehydrogenases

The Cytochrome System 6 points along pathway where hydrogen is released and temporarily bound to NAD Reduced coenzyme NADH 2 transfers hydrogen to a chain of hydrogen carriers called cytochrome system These systems are attached to the cristate of every mitochondrion

Transfer of hydrogen from each NADH 2 along system -produces 3 ATP -process called oxidative phosphorylation Complete oxidation of glucose yields 38 ATP -2 during glycolysis -36 during oxidative phosphorylation

The role of oxygen Final hydrogen acceptor Combines to form water Controlled by enzyme cytochrome oxidase Presence of oxygen also essential for hydrogen to pass along the cytochrome system

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