AP Biology Light Independent Reactions Calvin Cycle Photosynthesis
AP Biology Light Independent Reactions – Calvin Cycle
Photosynthesis Light Reaction
Photosynthesis Calvin Cycle
Calvin Cycle step 1
Carbon Fixation • Part 1 of the Calvin Cycle: – 3 Carbon Dioxides enter the cycle and combine with Ru. BP to create 3 very unstable 6 carbon molecules. – These 6 -carbon molecules instantly break down into 6, 3 -carbon molecules that are much more stable. – We now have all of the carbons in the cycle that are needed to make ½ of a glucose molecule.
Calvin Cycle step 2
Reduction • Part 2 of the Calvin Cycle: – ATP and NADPH are now used to modify the original 3 -carbon molecules in preparation for one of them to leave the cycle to make glucose. – This stage is called reduction because electrons are added to the 3 -carbon molecules to transform them into the building blocks for glucose. – ADP and NADP+ are sent back to the ETC.
Calvin Cycle step 3
Regeneration of Carbon Dioxide Acceptor • Part 3 of the Calvin Cycle: – The remaining 3 -carbon molecules are further modified using ATP to get back to the starting material in the cycle. – If you trace the number of carbons through the cycle, you should end up with the same amount that you started with. – The cycle starts with 15 carbons and at the end of the third phase you should have 15 carbons. – What happens if the plant has no carbon dioxide?
Calvin Cycle Intermediates
C 4 Plants and Photorespiration Photosynthetic cells of C 4 plant leaf Mesophyll cell PEP carboxylase Mesophyll cell Bundlesheath cell CO 2 The C 4 pathway Oxaloacetate (4 C) PEP (3 C) Vein (vascular tissue) ADP Malate (4 C) ATP C 4 leaf anatomy Stoma Bundlesheath cell Pyruvate (3 C) CO 2 CALVIN CYCLE Sugar Vascular tissue
CAM Plants and Photorespiration Sugarcane Pineapple CAM C 4 CO 2 Mesophyll cell Organic acid Bundlesheath cell CO 2 incorporated into four-carbon Organic acid organic acids (carbon fixation) CO 2 CALVIN CYCLE Sugar Spatial separation of steps CO 2 Organic acids release CO 2 to Calvin cycle Night Day CALVIN CYCLE Sugar Temporal separation of steps
Stomata of Leaves & Transpiration
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