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Cellular Respiration

Learn about the process of cellular respiration, where glucose is broken down into carbon dioxide, water, and energy. Understand the four separate reactions involved in cellular respiration: Glycolysis, Transition Reaction, Krebs Cycle, and Electron Transport. This process requires oxygen and produces a total of 38 ATP.

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Cellular Respiration

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  1. Cellular Respiration Dr. Huq

  2. Chapter 5

  3. Respiration • Overview; • Glucose to Carbon dioxide + Water +Energy • C6H12O6 + O2 6CO2 + 6H2O + 38 ATP • Glucose is highly reduced; contains energy • Oxygen receives the electrons to form energy • 4 separate reactions • Glycolysis, Transition Reaction, Krebs Cycle, Electron Transport, Chemiosomosis • Requires Oxygen Chapter 5

  4. Chapter 5

  5. Chapter 5

  6. Cellular Respiration By cellular respiration the pyruvic acid molecules are broken down completely to form three carbon dioxide molecules, and three molecules of water. In glycolysis, a total of four molecules of ATP are produced, but two are used up in other steps in the process. Additional ATP is produced during the Krebs Cycle and the Electron Transport Chain, resulting in a grand total of 40 ATP molecules produced from the breakdown of one molecule of glucose via cellular respiration. Chapter 5

  7. Cellular Respiration Steps There are three steps in the process of cellular respiration: glycolysis, the Krebs cycle, and the electron transport chain. Chapter 5

  8. Glycolysis- 10 steps • Glucose is Phosphorylated to form Fructose 1,6-diphosphate • Split to form 2 Glyceraldehyde 3-phosphate • Final Products are: • 2 Pyruvic Acid (C3H4O3) • Compare to original glucose - C6H12O6 • 2 NADH • 2 ATP Chapter 5

  9. Glycolysis There are two important ways a cell can harvest energy from food: fermentation and cellular respiration. Both start with the same first step: the process of glycolysis which is the breakdown or splitting of glucose (6 carbons) into two 3-carbon molecules called pyruvic acid. Chapter 5

  10. Glycolysis • Glycolysis happens in the cytoplasm of cells, not in some specialized organelle. • Glycolysis is the one metabolic pathway found in all living organisms. • Glycolysis does not need oxygen as part of any of its chemical reactions. It serves as a first step in a variety of both aerobic and anaerobic energy-harvesting reactions. Chapter 5

  11. Kreb’s Cycle • Figure E.3, A29 • Acetyl CoA  Carbon Dioxide • C2H4O2 to CO2 • Energy produced/Acetyl CoA (x2 for /Glucose) • 3 NADH • 1 FADH • 1 ATP • Metabolic Wheel • Fats, amino acids, etc. enter or leave • Citrate is product of first reaction • Simmons Citrate Media Chapter 5

  12. In eukaryotes, the Krebs Cycle and Electron Transport Chain occur within the mitochondria. The pyruvic acid resulting from glycolysis is sent into the mitochondria for these reactions to occur. To move one molecule of pyruvic acid from the cytoplasm into a mitochondrion “costs” the cell one molecule of ATP (therefore two ATPs for a whole glucose), thus a net total of 36 ATP molecules per molecule of glucose is produced in eukaryotes as compared to only two in fermentation. The overall reaction for cellular respiration is C6H12O6 + 6O2        6CO2 + 6H2O (+ energy for the cell to use for other things). Chapter 5

  13. Krebs cycle In this cycle, discovered by Hans Krebs, the pyruvic acid molecules are converted to CO2, and two more ATP molecules are produced per molecule of glucose. First, each 3-carbon pyruvic acid molecule has a CO2 broken off and the other two carbons are transferred to a molecule called acetyl coenzyme A, while a molecule of NADH is formed from NAD+ for each pyruvic acid (= 2 for the whole glucose). These acetyl CoA molecules are put into the actual cycle, and after the coenzyme A part is released, eventually each 2-carbon piece is broken apart into two molecules of CO2. In the process, for each acetyl CoA that goes into the cycle, three molecules of NADH, one molecule of FADH2, and one molecule of ATP are formed (= 6 NADH, 2 FADH2, and 2 ATP per whole glucose). Chapter 5

  14. Chapter 5

  15. Pyruvic Acid + 2 H++ 3 O2 3 Carbon Dioxide + 3 H2O+ 34 ATP Chapter 5

  16. Fermentation Products fromPyruvate • Homolactic = Lactic Acid • Yogurt, Lactobacillus • Alcohol + CO2 • Propionic Acid • Butyric Acid • Acetic Acid • Succinic Acid • Butylene to Acetoin • basis for VP Test (Vogues-Proskauer) Chapter 5

  17. Fermentation Lactic acid fermentation is done by some fungi, some bacteria, in yogurt, and sometimes by our muscles. Under greater exertion when the oxygen supplied by the lungs and blood system can’t get there fast enough to keep up with the muscles’ needs, our muscles can switch over and do lactic acid fermentation. In the process of lactic acid fermentation, the 3-carbon pyruvic acid molecules are turned into lactic acid. Chapter 5

  18. Fermentation Products • Alcohol and Carbon Dioxide • Yeast mostly • Lactic Acid • Humans, muscles without oxygen • Bacteria (Lactobacillus-yogurt) • Butyric Acid • Rancid butter, Clostridium-gangrene • Acetoin • Butanediol fermentation in Klebsiella • Propionic Acid • Swiss Cheese Chapter 5

  19. Fermentation In fermentation pyruvic acid molecules are turned into some “waste” product, only two ATP molecules per molecule of glucose – against four are produced in glycolysis. two of the most common types are lactic acid fermentation and alcohol fermentation. Chapter 5

  20. Fermentation Alcohol fermentation is done by yeast and some kinds of bacteria. The “waste” products of this process are ethanol and carbon dioxide (CO2). Humans have long taken advantage of this process in making bread, beer, and wine. In bread making, it is the CO2 that causes the bread to rise. Chapter 5

  21. Transition Reaction • Pyruvic Acid  Acetyl - Co A + CO2 + NADH • C2H4O2 Chapter 5

  22. The electron transport chain is a system of electron carriers embedded into the inner membrane of a mitochondrion. As electrons are passed from one compound to the next in the chain, their energy is harvested and stored by forming ATP. For each molecule of NADH which puts its two electrons in, approximately three molecules of ATP are formed, and for each molecule of FADH2, about two molecules of ATP are formed. Chapter 5

  23. At the last step in the electron transport chain, the “used up” electrons, along with some “spare” hydrogen ions are combined with O2 (we finally got around to the O2) to form water as a waste product: 4e- + 4H+ + O2      2H2O. Chapter 5

  24. Summary of Respiration • Aerobic Respiration • Glycolysis • Transition Rx. • Kreb’s Cycle • Electron Transport Chain • Anaerobic Respiration • Pyruvate  • Lactic Acid • Mixed Acids • Alcohol + CO2 • Recycle NADH • 2 ATP / Glucose Chapter 5

  25. Chapter 5

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