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Cellular Respiration Chapter 9 Cellular Respiration • Process by which mitochondria break down food molecules to make ATP • C6H12O6 + O2 CO2 + H2O + Energy • Three Stages: – Glycolysis – Citric Acid Cycle (Krebs Cycle) – Electron Transport Chain Anaerobic vs. Aerobic Anaerobic • Without oxygen • Glycolysis, Fermentation • Obligate Anaerobe – Cannot survive in the presence of oxygen – Tetanus • Facultative Anaerobe – Can use oxygen, but can survive in its absence – Yeast Aerobic • Uses Oxygen • Krebs and e- transport chain • Produces a lot more energy Glycolysis • Occurs in the cytoplasm of the cell • Breaks down glucose ( 6-Carbon) into 2 pyruvic acid (3-Carbon) • Makes 4 ATP, but uses 2 ATP = 2 ATP • NAD+ accepts electrons to become NADH – Those e- move to the e- transport chain Summary: Glycolysis makes 2 ATP, NADH, and 2 pyruvic acid. Citric Acid Cycle • Begins after pyruvic acid is transformed into acetyl-CoA (this rxn also makes NADH) • Occurs in the matrix of the mitochondria • For every turn of the cycle the following are made: – – – – 1 ATP 2 CO2 3 NADH 1 FADH2 • This cycle happens twice for each glucose Electron Transport Chain • Located in the inner membrane of the mitochondria • Similar to the e- transport chain in photosynthesis • NADH and FADH2 supply the energized e• ATP is produced and H+ is pumped into the matrix of the mitochondria • As the ATP moves out of the mitochondria more ATP is made • Oxygen is the final e- acceptor at the end of the chain – results in the formation of water • Makes 32 ATP Summary of Cellular Respiration Glycolysis ATP NADH 2 net (4 total) 2 Pyruvate 2 CO2 AcetylCoA Pyruvic acid to Acetyl-CoA Krebs (In 2 turns) 2 Electron Transport Chain 32 6 FADH2 2 Other Products CO2 H2O The 36 ATP produced in cellular respiration represent only about 38% of the energy stored in the sugar – the rest of the energy is released as heat What if no oxygen is available? • Glycolysis will continue, but if NAD+ is not recycled it will stop, too. • Less energy is produced – only 2 ATP • Fermentation – cycles the NAD back to glycolysis, but does not produce energy Fermentation Lactic Acid Fermentation • Makes lactic acid, CO2, and NAD+ • Occurs in muscles when an oxygen debt is created Alcoholic Fermentation • Makes alcohol, CO2, and NAD+ • Yeast and some bacteria