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Cellular Respiration

Cellular Respiration. C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6H 2 O + 38 ATP. Cellular Respiration: An Overview. Process by which cells convert the energy in food (usually glucose) into usable ATP. Terms to Know… Oxidation = the loss of electrons Compound becomes more positive

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Cellular Respiration

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  1. Cellular Respiration C6H12O6 + 6 O2 6 CO2 + 6H2O + 38 ATP

  2. Cellular Respiration: An Overview Process by which cells convert the energy in food (usually glucose) into usable ATP. • Terms to Know… • Oxidation = the loss of electrons • Compound becomes more positive • Reduction = the gain of electrons • Compound becomes more negative • Electrons and protons (H+) travel TOGETHER • NAD+ = coenzyme derived from niacin; acts as a H+ and e- acceptor. AN ENERGY CARRIER!

  3. Cellular Respiration: An Overview

  4. Substrate-Level Phosphorylation • An enzyme transfers a phosphate group directly from an organic molecule to ADP to form ATP • The ATP produced in Glycolysis & the Krebs Cycle is produced by this method.

  5. Oxidative Phosphorylation(ETC + Chemiosmosis) • The production of ATP by using energy derived from the redox reactions of the Electron Transport Chain. • The enzyme ATP synthase is needed to phosphorylate the ADP to produce ATP. • Almost 90% of the ATP produced from cellular respiration is produced this way.

  6. Cellular Respiration Glucose ATP Glycolysis ATP Oxygen Absent Oxygen Present Anaerobic Respiration (Fermentation) Aerobic Respiration (Krebs Cycle & ETC)

  7. Glycolysis • “glucose-splitting” • Big Picture: • Glucose (6-C) is broken down into 2 molecules of pyruvate (3-C) • Occurs in the cytosol • Occurs with or without oxygen • Made up of 2 phases: • Energy investment phase • Energy yielding phase

  8. Glycolysis: Energy Investment Phase • Glucose is converted into 2 G3P (Glyceraldehyde-3-phosphate) • Requires 2 ATP

  9. Glycolysis: Energy-Yielding Phase • 2 G3P are converted into 2 Pyruvate (3C) molecules. • Dehydrogenase enzymes remove H from intermediate compounds and attach them to 2 NAD to produce 2NADH

  10. Net Gain in Glycolysis • 2 ATP - 2 ATP (Energy investment phase) + 4 ATP (Energy yielding phase) + 2 ATP • 2 NADH • Electron carriers • Will be used to make ATP later 

  11. Choices, Choices!  • If oxygen is absent, anaerobic respiration occurs • Fermentation • Yeast & some bacteria  alcoholic fermentation • Animal muscle lactic acid fermentation • If oxygen is present, aerobic respiration occurs • Krebs Cycle and Electron Transport Chain

  12. Cellular Respiration Glucose ATP Glycolysis ATP Oxygen Absent Oxygen Present Anaerobic Respiration (Fermentation) Aerobic Respiration

  13. Fermentation • 2 major types: • Alcoholic and lactic acid fermentation • NAD+ acts as a hydrogen acceptor during glycolysis • If the supply of NAD+ runs out, then glycolysis would have to stop. • Fermentation occurs as simply a means of recycling the NAD+, so that glycolysis can occur again.

  14. Alcoholic Fermentation • Occurs in some BACTERIA and YEAST • 2 step process: • Carbon dioxide is released from pyruvate (3-C), forming acetaldehyde (2-C) • Acetaldehyde is reduced by NADH (gains an electron), forming ethyl alcohol (ethanol) • NAD+ is regenerated, thereby allowing glycolysis to continue • Used to produce beer and wine

  15. Lactic Acid Fermentation • Occurs in ANIMALS • 1 step process: • Pyruvate is reduced by NADH (gains an electron), forming lactic acid • NAD+ is regenerated, thereby allowing glycolysis to continue • Occurs in muscle cells, causing muscle pain and fatigue

  16. Cellular Respiration Glucose ATP Glycolysis ATP Oxygen Absent Oxygen Present Anaerobic Respiration (Fermentation) Aerobic Respiration

  17. Aerobic Respiration • After glycolysis, most of the energy from glucose remains “locked” in 2 molecules of pyruvate • If oxygen is present, the pyruvate enters the mitochondrial matrix to complete the Krebs Cycle • Pyruvate (3-C) is converted to Acetyl CoA (2-C) • CO2 is released as a waste product • NADH is produced

  18. The Krebs Cycle • Yield per pyruvate molecule: • 4 NADH • 1 FADH2 • 1 ATP • 2 CO2 • Yield per glucose molecule (two turns of Krebs Cycle): • 8 NADH • 2 FADH2 • 2 ATP • 6 CO2 • CO2 released as a waste product

  19. Electron Transport Chain • The ETC converts the NADH and FADH2from glycolysis and the Krebs Cycle into ATP • Occurs in inner membrane of mitochondrion • The energy in each NADH molecule moves enough protons (H+) into the mitochondrial matrix to create 3 ATP • 1 FADH2  2 ATP

  20. The Electron Transport Chain • The electrons from NADH and FADH2 are passed from one electron acceptor molecule to another. • Each electron acceptor is more electronegative than the last. • Oxygen is the final electron acceptor e- ETC oxygen

  21. Chemiosmosis • Similarly to photosynthesis, the energy the electrons lose along the way moves H+ out of the matrix and into the intermembrane space of the mitochondrion • As H+ ions diffuse through the membrane, ATP synthase uses the energy to join ADP and a phosphate group  ATP

  22. Oxidative Phosphorylation: ETC & Chemiosmosis

  23. Aerobic Respiration: Total Energy Yield • Glycolysis: • 2 ATP (Net) • 2 NADH  6 ATP • Krebs Cycle: • 2 ATP • 8 NADH  24 ATP (ETC) • 2 FADH2  4 ATP (ETC) • TOTAL: • 8 ATP + 30 ATP  38 ATP

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