 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 is the process that converts light energy into chemical energy.  Uses a biochemical pathway.  Overall reaction is: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

 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 r_paul/images/484px- Simple_photosynthesis_overview_svg.png

 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.

 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)

 Plants that use photosynthesis to fix carbon are called C 3 plants.  Alternate pathways include C 4 plants and CAM plants. ◦ C4 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 —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 + 6O 2 6CO 2 + 6H 2 O + energy (ATP)

 Aerobic Respiration —oxygen is present: most efficient  Anaerobic Respiration —no oxygen is present: less efficient.  Both types start with 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.

 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 --occurs in the mitochondrial matrix. Two turns of the Krebs Cycle produce: ◦ 2 ATP molecules ◦ 4 CO 2 molecules ◦ 6 NADH molecule ◦ 2 FADH 2 molecules

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 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: molecules.

 Through Aerobic Cellular Respiration, a maximum of 38 ATP molecules can be produced from one glucose molecule. ◦ 2 from Glycolysis ◦ 2 from Krebs cycle ◦ from the Electron Transport Chain

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

 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

PHOTOSYNTHESISRESPIRATION FUNCTION Production of Glucose Oxidation of Glucose LOCATION chloroplasts mitochondria REACTANTS 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 PRODUCTS C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O EQUATION light 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 +6O 2 6CO 2 + 6H 2 O +ATP COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION Click to reveal