Cellular Respiration and Fermentation

1. Cellular Respiration and Fermentation Chapter 7, Sections 5 and 6

2. The Cellular isms • Metabolism: is the set of chemical reactions that occur in living organisms in order to maintain life. • These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. • Usually divided into two categories. • Catabolism and Anabolism • Catabolism: breaking down & releasing energy • Anabolism: building up & requires energy

3. A Metabolic Pathway called Cellular Respiration Cells harvest energy by breaking bonds and shifting electrons from one molecule to another. • aerobic respiration - final electron acceptor is oxygen • anaerobic respiration - final electron acceptor is a molecule other than oxygen

4. Aerobic Respiration Occurs in 3 Stages: • Glycolysis • The Kreb’s Cycle • Electron Transport Chain and ATP Synthase

5. Stage One - Glycolysis • Occurs in the cytoplasm • For each molecule of glucose that passes through glycolysis, the cell nets 2 ATP molecules and 2 pyruvic acid molecules • NADH carries 2 high energy electrons 2 NADH Glucose → 2 Pyruvic Acid 2 ATP

6. Stage Two – The Kreb’s Cycle • Occurs in the matrix of the mitochondrion where the needed enzymes are dissolved • As pyruvic acid diffuses into the mitochondrion, each 3C molecule loses a molecule of CO2 and is converted into acetyl coenzyme A, or acetyl CoA 1 NADH 2 NADH Glucose → 2 Pyruvic Acid 2 Acetyl CoA 2 ATP 2 CO2

7. Stage Two – The Kreb’s Cycle (con’t) • Acetyl CoA is oxidized in a series of reactions • Named after biologist Hans Krebs who first explained the steps in the 1930s

8. Stage Two – The Kreb’s Cycle (con’t) Acetyl CoA 3 NADH + 1 FADH2 KREB’SCYCLE ATP CO2 CO2 After 2 cycles, 6 NADH, 2 FADH2, 4 CO2, and 2 ATP molecules are produced

9. Stage Three: The Electron Transport Chain • NADH molecules carry electrons to the inner mitochondrial membrane, where they transfer electrons to a series of membrane-associated proteins (electron carriers). • Eventually the electrons are pulled towards OXYGEN and combine with hydrogen ions, forming water

10. Stage Three: ATP Synthase Action • The ATP released in the ETC is used to move H+ ions across the membrane from low to high concentrations • This stores potential energy (positive side vs negative side) • ATP synthase is a protein in the membrane that spins like a mini turbine as H+ ions flow back across the membrane • The spinning ATP synthase generates 32-34 ATP molecules from ADP per original glucose molecule

11. ATP Synthase

12. Adding up the ATP from Cellular Respiration Mitochondrion Glycolysis 2 Acetyl- CoA Krebs Cycle 2 Pyruvic acid Electron Transport Glucose Maximum ATP per glucose: ATP Synthase

13. Harvesting Energy WITHOUT Oxygen • If oxygen is not available to capture the 2 low energy electrons at the end of the ETC, the Kreb’s cycle and the ETC will stop producing ATP • Glycolysis will continue to generate 2 ATP molcules, 2 NADH, and 2 Pyruvic Acid molecules • NADH reacts with the pyruvic acid, making NAD+ available to carry electrons so glycolysis can continue making ATP

14. ALCOHOLIC Pyruvic Acid → CO2 + ethyl alcohol Occurs in yeast CO2 makes dough rise and bubbles in beer & champagne Ethyl alcohol makes alcoholic beverages LACTIC ACID Pyruvic Acid → Lactic Acid Occurs in muscles during vigorous exercise (can feel “burn”) Occurs in prokaryotes used to make cheese, yogurt, sour cream, and sauerkraut Two Types of Fermentation