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Chapter 8

Chapter 8. Cellular Respiration. Chemical Pathways. One gram of the glucose, releases 3811 calories of heat energy when burned aerobically A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius

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Chapter 8

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  1. Chapter 8 Cellular Respiration

  2. Chemical Pathways • One gram of the glucose, releases 3811 calories of heat energy when burned aerobically • A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius • Cells release the energy from glucose and other food compounds

  3. Cellular Respiration • Process that releases energy by breaking down food molecules in the presence of oxygen • Takes place in the mitochondria • C6H12O6 + 6 O2----> 6 CO2 + 6 H2O + ATP • Occurs in three main stages: glycolysis, Krebs Cycle, and ETC

  4. Glycolysis • Is the first step of cellular respiration • It is an anaerobic process which means that it does not require oxygen to proceed • Requires an input of energy (ATP) • Occurs in the cytoplasm • Is the splitting of sugar (glucose) • Releases only a small amount of energy but the process is fast; can produce thousands of ATP molecules in a few milliseconds • Produces two molecules of a 3 carbon compound, PGA • The net yield is 2 ATP, 2 NADH, and 2 molecules of pyruvate

  5. Fermentation • Anaerobic process that follows glycolysis when oxygen is not available to the cell. • Converts pyruvate and NADH into NAD+ so that glycolysis can continue

  6. Alcoholic Fermentation • Another way in which NADH is converted back to NAD+ • Produces alcohol and CO2 • The CO2 produced by yeast makes the dough rise and bubbles appear in beer and sparkling wines • Pyruvic acid + NADH–> Alcohol +CO2+ NAD+ • Is useful to the brewery and baking industry

  7. Lactic Acid Fermentation • One way in which NADH is converted back to NAD+ • Lactic acid is produced • Occurs when we exercise, and our body has used up all of the ATP. Our muscles start burning and are sore after exercising. It also causes muscle fatigue. • Pyruvic Acid + NADH—>Lactic Acid + NAD+

  8. The CAC, Krebs Cycle, or TCA Cycle(2nd Step of Cellular Respiration) Follows glycolysis if oxygen is available to the cell Pyruvic acid travels from the cytoplasm to the mitochondria and is broken down into carbon dioxide in a series of energy extracting reactions Is an aerobic process (requires oxygen)

  9. Steps of the CAC Cycle, Krebs Cycle, or the TCA Cycle • Pyruvic acid is broken down into CO2 and 2C Acetyl groups which is bound briefly to acetyl CoA • 2 Carbons are passed into the Kreb Cycle to combine with a 4 carbon compound, (Oxaloacetate), to produce a 6C compound, citric acid. • 2 C atoms are removed (in 2 molecules of CO2)

  10. Steps Cont’d • 3 Molecules of NAD+ are converted to NADH • 1 Molecules of FAD converted to FADH2 • 1 Molecule of ADP converted to ATP or GDP to GTP Cycles through twice to breakdown down both molecules of pyruvate

  11. Electron Transport in the Mitochondria (3rd Step of Cellular Respiration) • Is a series of molecules along which electrons are transferred, releasing energy • Carrier molecules bring electrons from glycolysis and the Krebs Cycle to the ETC • The molecules are located on the inner membranes of the mitochondria • Is an aerobic process because oxygen is the final electron acceptor

  12. Electron Transport in the Mitochondria (3rd Step of Cellular Respiration) • Carrier molecules NADH and FADH2 give up electrons that pass through a series of reactions • At least 15 carrier proteins are involved in the ETC • At the top of the chain, the electrons have high energy, as they pass through the ETC, the energy given off is captured in molecules of ATP

  13. Electron Transport in the Mitochondria (3rd Step of Cellular Respiration) • High Energy electrons from NADH and FADH2 are passed along a series of E.T. enzymes in the inner membrane of the mitochondria • At the end of the chain, an enzyme combines electrons from the ETC, H+, and O2 from H20 • Produces 34 molecules of ATP

  14. ATP formation • H+ ions are pumped from the inside of the IM to the outside • The outside is more positively charged than the inside • The difference in charge supplies energy to make ATP from ADP

  15. Adenine Ribose Phosphate Groups ATP Molecule

  16. Energy in Balance • Photosynthesis-deposits energy • Respiration-withdraws energy • The equation from photosynthesis and the complete breakdown of glucose are the reverse of each other • The products of photosynthesis are the reactants of cellular respiration and vice versa

  17. Total ATP Production • Glycolysis-net gain of ATP =2 ATP • 2 NADH x 3 =6 ATP • Pyruvate into Acetyl CoA • 1 NADH x 3 x 2 cycles =6 ATP • Krebs Cycle =2 ATP • 3 NADH x 3 x 2 cycles =18 ATP • 1 FADH2 x 2 x 2 cycles =4 ATP • Total =38 ATP

  18. Overview of Cellular Respiration • Begins with glycolysis • Krebs Cycle is 2nd stage • Electron Transport Chain is the 3rd stage; transports e- • Results in the formation of 36-38 molecules of ATP • C6H12O6 + 6O2 ------> 6CO2 + 6H2O + ATP

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