1. Fermentation & Anaerobic Respiration Chapter 9.5-9.6

2. LEARNING TARGET 5 I can explain how fermentation and anaerobic respiration allow cells to produce ATP without the use of oxygen.

4. With Oxygen = Aerobic When O 2 is present in the cell… Glycolysis  “prep” step  Krebs cycle  ETC

5. Without Oxygen = Anaerobic When no O 2 is present in the cell, glycolysis is followed by fermentation Pyruvate  Fermentation Regenerates NAD+ carriers to allow glycolysis to continue ◦ This changes NADH back to NAD+ so it is available for removing H and e- from PGAL. This keeps glycolysis going! Plants undergo alcoholic fermentation Animals undergo lactic acid fermentation

6. Lactic Acid Fermentation Pyruvate → lactic acid + NAD + Human muscle cells when oxygen is low during exercise Lactic acid builds up in muscle tissue, causing soreness

7. Alcoholic Fermentation Pyruvate → CO 2 + alcohol + NAD + Used by microorganisms to make beer/wine Used by yeast to make bread ◦ CO 2 causes the “holes” in bread; why bread rises Facultative anaerobes ◦ Can switch back and forth between fermentation/respiration depending on O 2 availability

8. So why be able to do both? Isn’t aerobic CR better than fermentation?

9. Evolutionary Links Glycolysis = Most widespread metabolic pathway Earliest fossil bacteria (3.5 billion years ago) but large amounts of oxygen not present until 2.7 BYA Works without oxygen ◦ Suggests ancient prokaryotes probably used glycolysis to make ATP before oxygen was present Happens in cytoplasm without mitochondria ◦ Suggests it was in early prokaryotic cells before eukaryotes appeared ◦ Eukaryotes appeared 1 billion years after prokaryotes (endosymbiotic theory)

10. Other Fuel Molecules Fats, proteins, and carbohydrates can be broken down to release energy ◦ 1g of fat  twice as much ATP as 1g of carbohydrate Beta oxidation of fats ◦ Breakdown of fatty acids into 2 carbon fragments that can enter the Krebs cycle as Acetyl CoA Protein is broken into amino acids ◦ Most used by cell to build protein ◦ Excess amino acids converted into intermediates of glycolysis and Krebs and enters respiration that way Carbohydrates broken down to monomers to fuel respiration