Anaerobic Energy-Releasing Pathways AP Biology Fall 2010
Jan 21, 2016
Anaerobic Energy-Releasing Pathways
AP BiologyFall 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 diverseMany die when exposed to oxygenOthers 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 fermentationSupporting quick, non-sustained demands
for energy
1. T/F Yeast is used in bread making because it produces carbon
dioxide2. T/F In lactate fermentation FAD is
regenerated 3. T/F Fast twitch muscles are dark red
and support steady, prolonged material
1. True2. False NAD+ is regenerated 3. False This describes slow twitch
muscles