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Understanding Cellular Respiration: Redox Reactions & Energy Transfer

Explore the intricate process of cellular respiration, from oxidation to ATP synthesis, and learn how our bodies convert food into energy. Dive into Glycolysis, Krebs Cycle, and Electron Transport Chain for a comprehensive understanding of energy production in cells.

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Understanding Cellular Respiration: Redox Reactions & Energy Transfer

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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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