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Ch. 9-1 Chemical Pathways

Ch. 9-1 Chemical Pathways. Chemical Energy and Food. One gram of the sugar glucose, when burned in the presence of oxygen, releases 3811 calories of heat energy. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius

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Ch. 9-1 Chemical Pathways

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  1. Ch. 9-1 Chemical Pathways

  2. Chemical Energy and Food • One gram of the sugar glucose, when burned in the presence of oxygen, releases 3811 calories of heat energy. • A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius • The Calorie (capital “C”) that is used on food labels is a kilocalorie, or 1000 calories.

  3. Chemical Energy and Food • This process begins with a pathway called glycolysis.

  4. Overview of Cellular Respiration • In the presence of oxygen, glycolysis is followed by the Krebs cycle and the electron transport chain. • Glycolysis, the Krebs cycle, and the electron transport chain make up a process called cellular respiration.

  5. Overview of Cellular Respiration • Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

  6. Glycolysis • Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound

  7. ATP Production • Even though glycolysis is an energy-releasing process, the cell needs to burn 2 molecules of ATP to get things going. • Although the cell uses 2 ATP molecules to start glycolysis, when glycolysis is complete, 4 ATP molecules have been produced.

  8. NADH Production • One of the reactions of glycolysis removes 4 high-energy electrons and passes them to an electron carrier called NAD+, or nicotinamide adenine dinucleotide. • Like NADP+ in photosynthesis, each NAD+ accepts a pair of high-energy electrons. • By doing this, NAD+ helps to pass energy from glucose to other pathways in the cell.

  9. fermentation • Fermentation releases energy from food molecules by producing ATP in the absence of oxygen. • Because fermentation does not require oxygen, it is said to be anaerobic. The term anaerobic means “not in air”. • The 2 main types of fermentation are alcoholic fermentation and lactic acid fermentation.

  10. Alcoholic fermentation • Yeasts and a few other microorganisms use alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes. The equation for alcoholic fermentation after glycolysis is:

  11. Alcoholic fermentation • Pyruvic acid + NADH  alcohol + CO2 + NAD+ • Alcoholic fermentation produces carbon dioxide as well as alcohol.

  12. Lactic acid fermentation • In many cells, the pyruvic acid that accumulates as a result of glycolysis can be converted to lactic acid. • Because this type of fermentation produces lactic acid, it is called lactic acid fermentation. • This process regenerates NAD+ so that glycolysis can continue.

  13. Lactic Acid Fermentation • The equation for lactic acid fermentation after glycolysis is: • Pyruvic acid + NADH  lactic acid + NAD+ • Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues. • Unicellular organisms also produce lactic acid as a waste product during fermentation.

  14. Lactic Acid Fermentation • Cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut, and kimchi are also produced by lactic acid fermentation.

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