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Bioenergetics

Bioenergetics. Obtaining Energy. Organisms must be able to transform energy from one form to another. Autotrophs —can transform energy from sunlight into chemical energy (can make food). Then use the food energy for life processes.

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Bioenergetics

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  1. Bioenergetics

  2. Obtaining Energy • Organisms must be able to transform energy from one form to another. • Autotrophs—can transform energy from sunlight into chemical energy (can make food). Then use the food energy for life processes. • Heterotrophs—obtain energy for life processes by eating food.

  3. Photosynthesis • Photosynthesis is the process that converts light energy into chemical energy. • Uses a biochemical pathway. • Overall reaction is: 6CO2 + 6H2O C6H12O6 + 6O2

  4. The Stages of Photosynthesis • There are two stages to the process • Light Reactions —light energy is converted to chemical energy, which is temporarily stored in ATP and the energy carrier molecule NADPH • Dark Reactions (Calvin Cycle)—organic compounds are formed using CO2 and the chemical energy stored in ATP and NADPH http://bioweb.uwlax.edu/bio203/s2009/schroeer_paul/images/484px-Simple_photosynthesis_overview_svg.png

  5. Light Reactions • Require lightand chlorophyll. • Take place in thylakoid membranes of the chloroplast. • Products of the light reactions are NADPHand ATP. • These are sent to the Calvin Cycle (dark reactions) • The oxygenreleased by photosynthesis comes from the splitting of water. • A hydrogen ion gradient through ATPsynthasedrives the synthesis of ATP. • The electron transport chain drives the synthesis of NADPH.

  6. The Calvin Cycle • Does not require light. • Happens in the stromaof the chloroplasts and requires CO2. • Uses the energy stored in the ATP and NADPH from the light reactions to produce organic compounds in the form of sugars. • Most common pathway for carbon fixation (changing CO2 into carbohydrates)

  7. Alternate Pathways • Plants that use photosynthesis to fix carbon are called C3 plants. • Alternate pathways include C4 plants and CAMplants. • C4 plants: corn, sugar cane and crab grass. • This pathway uses an enzyme to fix CO2 into a four carbon sugar and conserves water. • CAM plants: cactuses, pineapples, and jade plants • Open stomata at night and close during day to prevent water loss.

  8. Cellular Respiration • Cellular Respiration —the process by which cells get energy from carbohydrates; oxygen combines with glucose to form water and carbon dioxide C6H12O6 + 6O2 6CO2 + 6H2O + energy (ATP)

  9. Aerobic and Anaerobic Respiration • Aerobic Respiration —oxygen is present: most efficient • Anaerobic Respiration —no oxygen is present: less efficient. • Both types start with glycolysis.

  10. Glycolysis • One glucose (6C) is broken into two molecules of pyruvic acid (3C). Occurs in cytosol. No oxygen is needed. 2% efficient. • If oxygen is available, the pyruvic acid will move into the mitochondria and aerobic respiration will begin. • 4 ATP molecules are produced. Two are used to break apart the next glucose molecule and keep glycolysis going. • This leaves a net yield of 2 ATP molecules for use by the cell. • Two NAD+ are converted into 2 NADH and 2H+. These go to Electron Transport.

  11. Aerobic Respiration • In most cells, the pyruvic acid produced in glycolysis enters the pathway of aerobic respiration. • More efficient than glycolysis. • Oxygenis required. • There are two major stages: The Krebs Cycle and the Electron Transport Chain

  12. The Krebs Cycle • The Krebs Cycle --occurs in the mitochondrial matrix. Two turns of the Krebs Cycle produce: • 2 ATP molecules • 4 CO2 molecules • 6 NADH molecule • 2 FADH2 molecules

  13. http://www.methuen.k12.ma.us/mnmelan/Respiration%20L2.htm

  14. Electron Transport Chain • The Electron Transport Chain, linked with chemiosmosismakes up the second stage of aerobic respiration. • Electrons are transferred from one molecule to another by several electron carrying molecules located in the membrane of the mitochondria. • All steps occur in the cristae(inner membrane) • This step generates the most amount of ATP: 32-34 molecules.

  15. Efficiency of Cellular Respiration • Through Aerobic Cellular Respiration, a maximum of 38 ATP molecules can be produced from one glucose molecule. • 2 from Glycolysis • 2 from Krebs cycle • 32-34 from the Electron Transport Chain

  16. Anaerobic Respiration • If no oxygen is present, the Krebs Cycle and Electron Transport Chain are not utilized. • Fermentation is used instead.

  17. Fermentation • Fermentation is the chemical pathway that recycles NAD+ in the absence of oxygen. It keeps glycolysis going. No additional ATP is made. Therefore, you still have the 2% efficiency rate for energy release. • Two types of fermentation: • Lactic Acid Fermentation • Alcoholic Fermentation

  18. Click to reveal COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION

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