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Respiration

nydailynews.com. Respiration. LECTURE #10. Redox Reactions. Oxidation The loss of electrons Reduction The gain of electrons * Oxygen is not always involved. * Electrons in Redox reactions travel down an energy hill. NAD.

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Respiration

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  1. nydailynews.com Respiration LECTURE #10

  2. Redox Reactions • Oxidation • The loss of electrons • Reduction • The gain of electrons * Oxygen is not always involved. * Electrons in Redox reactions travel down an energy hill.

  3. NAD The most important electron carrier in energy transfer • This coenzyme exists in 2 forms: • Empty: NAD+ • Oxidized (low energy) form • Carrying electrons: NADH • Reduced (high energy) form

  4. How NAD works

  5. Cellular Respiration • The formula for cellular respiration: C6H12O6 + O2 CO2 + H2O + energy • Many separate steps and three key phases are involved in the oxidization of glucose: • Glycolysis • Krebs cycle • Electron transport chain (ETC)

  6. Products of each phase • Glycolysis • Some ATP and NADH produced • Krebs cycle • Some ATP and NADH produced • Electron transport chain • NADH oxidized to produce 32 ATP

  7. Our bodies can use only ATP (rather than food or glycogen or fats) as a direct source of energy. The energy contained in food is transferred to ATP during respiration.

  8. Glycolysis • Cytosol • Glucose  2 pyruvate molecules • Pyruvate is slightly more oxidized than glucose • Net production of 2 ATP, 2 NADH

  9. Transition step • The 2 pyruvate molecules produced during glycolysis are combined with acetyl coenzyme A Products: • 2 acetyl CoA molecules • 2 CO2 molecules • 2 NADH molecules ** This brings the products of glycolysis into the mitochondrion.

  10. Krebs Cycle • Inner compartment of mitochondria • The 2 acetyl CoA produced in the transition step are fully oxidized to form CO2

  11. Krebs Cycle • Acetyl CoAcombines with oxaloacetate = Citric acid • Through multiple steps, citric acid is oxidized into oxaloacetate • Electrons captured • CO2 released

  12. Electron Transport Chain • Embedded within the inner membrane • Three large enzyme complexes • Two small mobile molecules

  13. Electron Transport Chain Reduced coenzymes (NADH) donate their high-energy electrons to an electron carrier in the ETC. They also donate hydrogen ions (H+). Movement of electrons along the ETC releases energy that powers the pumping of H+ across the membrane into the outer compartment of the mitochondrion.

  14. Electron Transport Chain • Oxygen is the final electron acceptor Oxygen atom accepts 2 electrons and 2 H+ from the ETC and forms one molecule of water: Oxygen atom + 2H+ + 2e- H2O

  15. ATP synthesis • H+ move back across the membrane into the inner compartment by a type of diffusion called chemiosmosis. • Moves down concentration gradient • Movement of H+ through the enzyme ATP synthase powers the production of ATP. • ATP synthase rotates, providing mechanical energy to push the third phosphate group onto ADP.

  16. Products of aerobicrespiration • 36 ATP are produced by the breakdown of a single glucose molecule.

  17. Other energy sources • Other molecules are converted into glucose, pyruvate, or another intermediate in cellular respiration.

  18. Discussion Glucose + O2 CO2+ H2O + energy • Where is each of the above usedor produced during cellular respiration?

  19. Fermentation • Some energy can still be harvested in the absence of O2 • In fermentation, glycolysis is the only energy-yielding process • Used by yeast, anaerobic bacteria, and sometimes our muscles stuffeducatedlatinoslike.wordpress.com

  20. Fermentation • Glycolysis produces 2 ATP, 2 NADH, 2 pyruvate • Pyruvate is converted to acetaldehyde and CO2 • Acetaldehyde (not oxygen) is reduced by NADH and thus forms ethanol! Acetaldehyde + NADH  ethanol + NAD+

  21. Wine production • Yeast is added to grape juice, and the mixture is placed in airless wine casks • Grape juice contains sugars • Yeast “ferment” these sugars • Ethanol concentrations lethal over about 14% winewithgraham.wordpress.com

  22. Lactate fermentation • Animal skeletal muscles are highly active • High demand for glucose and O2 • The speed of O2 delivery cannot meet the demand • Pyruvate is reduced by NADH to form lactic acid Pyruvate + NADH  lactic acid + NAD+ healthguide.howstuffworks.com

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