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Cellular Respiration

Cellular Respiration. How much energy is present in food?. One gram of the sugar glucose (C 6 H 12 O 6 ) 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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Cellular Respiration

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  1. Cellular Respiration

  2. How much energy is present in food? • One gram of the sugar glucose (C6H12O6) 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 that is used on food labels is a kilocalorie or 1000 calories. • Cell don’t “burn” glucose, but gradually release energy from glucose and other food compounds. This process begins with a pathway called glycolysis.

  3. Glycolysis only releases a small amount of energy. If oxygen is present, glycolysis leads to two other pathways that release a lot of energy. If no oxygen is present, glycolysis leads to another pathway. • 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.

  4. Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. 6O2+C6H12O66CO2+6H2O+Energy

  5. Glycolysis • Glycolysis is the process by which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound. • During glycolysis, 2 ATP molecules are used up, but 4 ATP molecules are produced= net gain of 2 ATP. • *Glycolysis does NOT require oxygen

  6. Fermentation • When oxygen is not present, glycolysis is followed by fermentation. Fermentation releases energy from food molecules by producing ATP in the absence of oxygen. • Cells convert NADH to NAD+ passing the electrons back to pyruvic acid. This allows glycolysis to continue producing ATP. • *This is an anaerobicprocess • The two main types of fermentation are alcoholic fermentation and lactic acid fermentation.

  7. Alcoholic Fermentation • Yeasts and other microorganisms use alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes. • Pyruvic acid+ NADHalcohol+ CO2 + NAD+ • Causes bread dough to rise. When the dough runs out of oxygen, it begins to ferment, giving off bubbles of CO2 that form the air spaces you see in a slice of bread. The small amount of alcohol produced evaporates.

  8. Lactic Acid Fermentation • In many cells, the pyruvic acid that accumulates as a result of glycolysis can be converted to lactic acid. • The process regenerates NAD+ so that glycolysis can continue. 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. Without oxygen, the body is not able to produce all of the ATP required. • When your exercise by running, swimming, or riding a bike as fast as you can, the large muscle cells quickly run out of oxygen. Your muscle cells rapidly produce ATP by lactic acid fermentation.

  9. The Krebs Cycle • In the presence of oxygen, pyruvic acid produced by glycolysis passes into The Krebs Cycle. • During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. • The ATP produced directly in the Krebs cycle can be used for cellular activities. • What does the cell do with all those high-energy electron carrier like NADH? • In the presence of oxygen, the high-energy electrons can be used to generate huge amounts of ATP.

  10. Electron Transport • The high-energy electrons produced in the Krebs cycle are passed to NADH and FADH2. The electrons are then passed from those carriers to the electron transport chain. • The electron transport chain uses high-energy electrons from the Krebs cycle to convert ADP into ATP. • At the end of the electron transport chain an enzyme combines the electrons with hydrogen ions and oxygen to form water. • Oxygen serves as the final electron acceptor of the ETC therefore oxygen is essential for getting rid of low-energy electrons and hydrogen ions, the wastes of cellular respirations. • Every time a pair of high-energy electrons moves down the ETC, the energy is used to move H+ ions across the membrane. These ions then rush back across the membrane, producing enough force to spin the ATP synthase and generate enormous amounts of ATP.

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