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Cellular Respiration

Cellular Respiration. CR is the process by which cells convert the energy in food, in the form of glucose, into usable energy (ATP) Terms to know Oxidation=the loss of electrons, compound becomes more positive Reduction=the gain of electrons, compound becomes more negative

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Cellular Respiration

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  1. Cellular Respiration

  2. CR is the process by which cells convert the energy in food, in the form of glucose, into usable energy (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, 2 electrons for every 1 H+(Proton)

  3. Glycolysis • Two types of cellular respiration include aerobic (with O2) and anaerobic (without O2) • “glucose-breaking • Glycolysis is the first step in both forms of CR, thus it does not need oxygen

  4. Big Picture • Glucose, C6H12O6 (a 6 carbon molecule) is broken down into 2 molecules of (a 3 carbon molecule) pyruvate • Occurs in the cytosol • Releases about 2% of the energy in glucose

  5. Input • 2 ATP, ”charged batteries” to use • 2 NAD • Glucose, energy storage molecule from food, C6H12O6 • Output: • 4 ATP (2 net ATP) • 2 NADH from NAD+ • 2 pyruvates – also known as pyruvic acid • Glucose breaks in half forming 2, 3 carbons chains

  6. If oxygen is absent, anaerobic respiration occurs • Fermentation • If plants, bacteria, or yeast is alcoholic fermentation • If animals is lactic acid fermentation • If oxygen is present, aerobic respiration occurs

  7. Anaerobic Respiration: Fermentation • 2 major types: alcoholic and lactic acid • Fermentation is used as a way to dispose of H+ produced during glycolysis • If the supply of NAD+ runs out, then glycolysis would stop • Thus the purpose of fermentation is to recycle NAD

  8. Anaerobic Respiration: Fermentation • Alcoholic Fermentation Occurs in plans, bacteria, and yeast -Normal process -Carbon dioxide is released from pyruvate (3C) forming acetaldehyde (2C) -Acetaldehyde is reduced by NADH (gains an electron) forming ethyl alcohol (ethanol) -NAD+ is regenerate allowing glycolysis to continue -Used to produce beer and wine

  9. Anaerobic Respiration: Fermentation • Lactic Acid Fermentation • Occurs in animal cells • Normal process • Pyruvate is reduced by NADH (gains an electron), forming lactic acid • NAD+ is regenerated allowing glycolysis to continue • Occurs in muscle cells, causing muscle pain and fatigue during rapid exercise when the body cannot supply enough oxygen to tissues

  10. Aerobic Respiration • After glycolysis, most of the energy from glucose remains “locked” in 2 molecules of pyruvate • If oxygen is present, pyruvate enters the mitochondrial matrix to complete the Kreb’s Cycle/The Citric Acid cycle (TCA) • First pryuvate gets “groomed” in the mitochondria by removing 1 C (CO2) and adding Coenzyme A

  11. Aerobic Respiration

  12. Aerobic Respiration • Kreb’s Cycle • The next step in aerobic respiration occurring in the matrix of the mitochondria • It’s a series of redox reactions starting with Acetyl CoA • Acetyl CoA (2C) binds with oxaloacetate (4C) forming a 6C compound. • Eventually the carbons from acetyl CoA get released as CO2, allowing oxaloacetate to go through the cycle again

  13. Aerobic Respiration • Kreb’s Cycle • Named after Hans Krebs, Nobel prize winner 1953 for discovering the cycle • Also called the citric acid cycle • Yields per pyruvate molecule: • 4 NADH, 1 FADH2, 1 ATP • Yields per glucose: • 8 NADH, 2 FADH2, 2 ATP

  14. Aerobic Respiration

  15. Aerobic Respiration • Electron Transport Chain and Chemiosmosis • The ETC is the last step in aerobic respiration • It receives all the electron carriers (NADH, FADH2) from glycolysis and Kreb’s cycle • It then converts NADH and FADH2 into NAD+ and FAD+ • Occurs in the inner membrane of the mitochondria

  16. Aerobic Respiration • Electron Transport Chain and Chemiosmosis • 1 NADH -> 3 ATP • 1 FADH2 -> 2 ATP • The electrons from NADH and FADH2 are passed from one electron acceptor protein to another • Oxygen is the final electron acceptor and makes water when it combines with hydrogens

  17. Aerobic Respiration • Chemiosmosis • The energy the electrons lose along the way moves H+ (off of NADH and FADH2) out of the matrix and into the intermembrane space of the mitochondria • As H+ ions diffuse through the membrane, the enzyme ATP synthase uses the energy to join ADP and a phosphate group -> ATP

  18. Aerobic Respiration • Electron Transport Chain • 38% efficient (some energy lost as heat) • 62% is released as heat (why you feel warmer after exercise) • 1 glucose yields 34-38 ATP • ATP made from glucose provides energy to sleep, exercise, eat, and study – allows cells to function • Glycolysis: 2 ATP, 2 NADH -> 6 ATP in ETC • Kreb’s: 2 ATP, 8 NADH-> 24 ATP in ETC, 2 FADH2 -> 4 ATP in ETC

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