Anaerobic Energy-Releasing Pathways AP Biology Fall 2010

Anaerobic pathways operate when oxygen is absent (or limited) Pyruvate from glycolysis is metabolized to produce molecules other than acetyl- CoA

Organisms that carry out fermentation (fermentors) are diverse Many die when exposed to oxygen Others use oxygen but switch when it becomes scarce Fermentation yields enough energy for many single-celled anaerobic organisms Sufficient for some aerobic cells when oxygen levels drop Insufficient for large, multi-celled organisms Lactose fermenting bacteria turn bright pink!

Fermentation begins with glucose degradation to pyruvate Cellular enzymes convert pyruvate to acetaldehyde, which then accepts electrons from NADH to become alcohol

Yeasts are valuable in the backing industry and in alcoholic beverage production Carbon dioxide by-product makes dough rise

Certain bacteria (as in milk) and muscle cells have the enzymes capable of converting pyruvate to lactate No additional ATP beyond the net two from glycolysis is produced NAD + is regenerated

When muscle cells are very active, they convert to producing lactate temporarily Slow stitch muscle fibers (dark red) Support steady, prolonged activity because they have many mitochondria making large quantities of ATP Fast twitch muscle fibers (light colour) have few mitochondria and produce small amounts of ATP by lactate fermentation Supporting quick, non-sustained demands for energy

1. T/FYeast is used in bread making because it produces carbon dioxide 2. T/FIn lactate fermentation FAD is regenerated 3. T/FFast twitch muscles are dark red and support steady, prolonged material

1. True 2. FalseNAD + is regenerated 3. FalseThis describes slow twitch muscles