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Cell Respiration

Learn why food is crucial, how it fuels cell respiration, and the energy conversion process, including glycolysis, fermentation, the Krebs Cycle, and Electron Transport Chain. Discover short-term vs. long-term energy sources.

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Cell Respiration

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  1. Cell Respiration Jennifer Naples DI Biology

  2. Why Do We Need Food? • How do you feel when you are hungry? • Stomach growls • Tired • Weak • Dizzy • Why do you feel that way? • Take 2 minutes to write down why your body acts the way it does when you are hungry?

  3. Why Do We Need Food? • Why do we need food? • Food provides our bodies with the chemical building blocks that we need to grow and reproduce. • Food is a source of raw materials from which our bodies make new molecules • Food is a source of energy

  4. Chemical Energy and Food • How much energy is in food? • A lot! • One gram of sugar (glucose)when burned 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 celcius • The calorie(capital “C”) that is used on food labels is a kilocalorie or 1,000 calories

  5. The Process of Cell Respiration • Cell respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. • The equation cell respiration is: • 602+C6H12O6 6CO2+6H2O+Energy • oxygen+glucose carbon dioxide+water+energy

  6. The Process of Cell Respiration • Cell respiration requires oxygen and glucose • Cell respiration releases carbon dioxide, water and energy • There are three stages of cell respiration: • Glycolysis • Krebs Cycle • Electron Transport Chain

  7. Glycolysis • The first stage of cell respiration • One molecule of glucose is broken in half • Produces 2 molecules of pyruvic acid • Occurs in the cytoplasm of a cell • Requires 2 molecules of ATP to start • Makes 2 molecules of ATP

  8. No Oxygen? • If there is no oxygen present glycolysis is followed by a pathway called fermentation • Fermentation releases energy from food molecules by producing ATP in the absence of oxygen • Fermentation is anaerobic – it requires NO oxygen

  9. Two Types of Fermentation • There are two types of fermentation • Alcoholic Fermentation and Lactic Acid Fermentation • Alcoholic Fermentation produces carbon dioxide and alcohol • Causes dough to rise • Gives of bubbles of carbon dioxide that form the air spaces that you see in bread.

  10. Lactic Acid Fermentation • Lactic acid fermentation produces lactic acid • Produced in your muscles during rapid exercise when the body can not supply enough oxygen to the tissues • Without oxygen your body is not able to produce all of the ATP required. • When you do vigorous exercise your body quickly begins to produce ATP through Lactic Acid Fermentation.

  11. Check for Understanding • What is Cell Respiration? • What are the products of glycolysis? • What are the two main types of fermentation? • What is a calorie? A Calorie?

  12. The Krebs Cycle • The second stage of cell respiration in the presence of oxygen • Pyruvic acid is broken down into carbon dioxide in a series of energy extracting reactions • Also called the citric acid cycle because citric acid is one of the compounds formed during this cycle

  13. The Krebs Cycle • The Krebs cycle occurs in the Mitochondrion • The Krebs Cycle produces high energy electrons that are used in the next cycle of cell respiration to create large amounts of ATP • The Krebs Cycle produces ATP

  14. Electron Transport Chain • High energy electrons that are produced in the Krebs Cycle are passed on to Electron Transport Chain. • Converts ADP into ATP

  15. ATP Totals • Glycolysis produces 2 ATP molecules per glucose • The Krebs Cycle produces 1 molecule of ATP • The Electron Transport Chain produces 33 molecules of ATP • Cellular Respiration produces 36 molecules of ATP and uses only 2 to get started

  16. Short VS. Long Term Energy • Quick energy like that used for a sprint is usually obtained through lactic acid fermentation • About a 50 meter mark ATP store are used up • Lactic acid build up is a by product of fermentation • The only way to get rid of the build up is through a chemical pathway that requires oxygen • That is why we breathe heavily after exercise

  17. Short VS. Long Term Energy • What happens when you are exercising for a long period of time? • Cell respiration is the only way to generate a continuing supply of ATP. • Cell respiration releases energy more slowly that fermentation • Energy is stores in muscle tissue and other tissues in the body(glycogen) which last for 15-20 minutes • After that your body begins to break down other stored molecules including fats for energy • That is why aerobic forms of exercise are beneficial for weight control

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