Bioenergetics Obtaining Energy Organisms must be able to
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. ◦ Heterotrophs —obtain energy for life processes by eating food.
Photosynthesis � Photosynthesis is the process that converts light energy into chemical energy. � Uses a biochemical pathway. � Overall reaction is: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2
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 CO 2 and the chemical energy stored in ATP and NADPH http: //bioweb. uwlax. edu/bio 203/s 2009/schroee r_paul/images/484 px. Simple_photosynthesis_overview_svg. png
Light Reactions � Require light and chlorophyll. � Take place in thylakoid membranes of the chloroplast. � Products of the light reactions are NADPH and ATP. � These are sent to the Calvin Cycle (dark reactions) � The oxygen released by photosynthesis comes from the splitting of water. � A hydrogen ion gradient through ATP synthase drives the synthesis of ATP. � The electron transport chain drives the synthesis of NADPH.
The Calvin Cycle � Does not require light. � Happens in the stroma of the chloroplasts and requires CO 2. � 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 CO 2 into carbohydrates)
Alternate Pathways � Plants that use photosynthesis to fix carbon are called C 3 plants. � Alternate pathways include C 4 plants and CAM plants. ◦ C 4 plants: corn, sugar cane and crab grass. �This pathway uses an enzyme to fix CO 2 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.
Cellular Respiration � Cellular Respiration —the process by which cells get energy from carbohydrates; oxygen combines with glucose to form water and carbon dioxide C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + energy (ATP)
Aerobic and Anaerobic Respiration � Aerobic Respiration —oxygen is present: most efficient � Anaerobic Respiration —no oxygen is present: less efficient. � Both types start with glycolysis.
Glycolysis � One glucose (6 C) is broken into two molecules of pyruvic acid (3 C). 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 2 H+. These go to Electron Transport.
Aerobic Respiration � In most cells, the pyruvic acid produced in glycolysis enters the pathway of aerobic respiration. � More efficient than glycolysis. � Oxygen is required. � There are two major stages: The Krebs Cycle and the Electron Transport Chain
The Krebs Cycle � The Krebs Cycle --occurs in the mitochondrial matrix. Two turns of the Krebs Cycle produce: ◦ ◦ 2 4 6 2 ATP molecules CO 2 molecules NADH molecule FADH 2 molecules
http: //www. methuen. k 12. ma. us/mnmelan/Respiration%20 L 2. ht m
Electron Transport Chain � The Electron Transport Chain, linked with chemiosmosis makes 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.
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
Anaerobic Respiration � If no oxygen is present, the Krebs Cycle and Electron Transport Chain are not utilized. � Fermentation is used instead.
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
Click to reveal COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION PHOTOSYNTHESIS RESPIRATION FUNCTION Production of Glucose Oxidation of Glucose LOCATION chloroplasts mitochondria REACTANTS 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 PRODUCTS C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O C 6 H 12 O 6 +6 O 2 EQUATION light 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O +ATP
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