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Published byMerry Gilmore Modified over 9 years ago
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I. Photosynthesis The process of converting light energy into chemical bond energy in the form of glucose Supplies energy and oxygen to virtually all living things
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II. Chloroplasts The site of photosynthesis Chloroplasts contain chlorophyll absorb light use energy to drive photosynthesis Three functional parts inside the chloroplast
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1. Intermembrane Space Chloroplasts is a double membrane Intermembrane space separates the two membranes
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2. Thylakoid Flattened membrane sacs inside chloroplast Chlorophyll is found here Light reactions take place here Grana stacks of thylakoids
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3. Stroma Fluid filled space that surrounds grana Reactions that use chemical energy to convert carbon dioxide to sugar occur here These are called dark-reactions
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III. Light Reactions Occur in the thylakoid membranes of chloroplasts Light energy excites a pair of electrons Electrons passed to different “carriers” – they lose a bit of energy at each step Generate ATP (photophosphorylation) and NADPH as they give off energy Give off oxygen as a by-product from splitting of water
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IV. Noncyclic Electron Flow Involve PS I and PS II Occurs in thylakoids Passes electrons continuously from water to NADP+ Produces ATP Produces NADPH Produces oxygen
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V. Cyclic Electron Flow Involves only PS I Makes ATP Does not produce NADPH or oxygen
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Bottom Line: Light reactions take energy from light and hold it for later use Held in ATP and NADPH
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VI. Calvin Cycle – the Dark Reactions Carbon-fixation reactions that assimilate 6 Carbons into a carbohydrate Occurs in the stroma ATP and NADPH produced by light reactions are used in the Calvin cycle to turn carbon dioxide to sugar NADPH provides the reducing power ATP provides the chemical energy
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More Calvin Cycle… End product of the Calvin Cycle is a glucose molecule Uses 18 ATP molecules and 12 NADPH molecules 3 CO2 + 6 NADPH + 5 H2O + 9 ATP → C3H5O3-PO32- + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi
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Bottom Line: Water donates electrons Light provides energy CO2 provides the carbons for sugar
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Photosynthesis As a Process Water is split, oxygen is released, sugar gets made from CO 2 …mmmmm…. sugar
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Energy for Photosynthesis OIL RIG Oxidation is loss of electrons, reduction is gain of electrons Photosynthesis is an endergonic process: energy is required to reduce carbon dioxide to sugar Light provides energy of electrons as they are moved from water to sugar
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Energy for Photosynthesis (cont’d) Water is split, electrons are transferred from the water to carbon dioxide (via NADPH), reducing it to sugar There are two separate parts to photosynthesis Light reactions (the “Photo”) Calvin Cycle (dark reactions) – (the “synthesis”)
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IV. Respiration – Returning the Energy We digest sugar, and energy is released in the form of ATP. Sugar gets oxidized (loses electrons) and the energy released makes ATP This happens in all cells of plants, animals, and bacteria The byproduct is CO2, which is then used to make new sugar through photosynthesis
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PHEW! Take a breather! On with Photosynthesis!!!
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III. Photosynthesis As a Process Light energy absorbed; CO 2 absorbed; O 2 released from water; sugar produced Plants split the water to release Hydrogen to make NADPH Plants absorb light to energize electrons in the thylakoid membrane Sugars provide a more useful storage form for the energy in the electrons released from water
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IX. The Good Stuff… Light reactions take energy in as light and store it as ATP and NADPH Dark reactions take the energy stored in ATP and NADPH to make sugar molecules *****We take glucose in and convert the energy in glucose back to ATP so our bodies can use it*****
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X. Three Types of Plants C3 plants: These include rice, wheat, beans Most plants are C3 which means 3- phosphoglycerate is produced C4 plants: crab grass and sugarcane, plants in hot regions They make a 4 carbon compound prior to the Calvin Cycle An adaptation for plants that grow in hot regions, when stomata are closed
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X. Three Types of Plants (cont’d) CAM plants: (crassulacean acid metabolism) Occurs in many desert dwelling plants such as cacti Open stomata at night instead of during the day. Carbon gets fixed at night. The only difference in these plants is the time of carbon fixation; they still all use the Calvin Cycle to produce sugar from CO 2
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