Two Stages of Photosynthesis Light Reaction aka light

The Calvin Cycle : C 3 carbon fixation In stroma of chloroplast Inputs CO

The Calvin Cycle : C 3 carbon fixation 3 turns of the cycle Rubisco

Calvin Cycle Accounting Per turn CO 2 1 Consume ATP 3 Consume NADPH 2

http: //www. science. smith. edu/departments/Biology/Bio 231/calvin. ht ml http: //faculty. nl. edu/jste/calvin_cycle. htm http:

This version of photosynthesis is used by 85% of plants - the C 3

In hot, dry conditions, plant will undergo Photorespiration • to conserve water, leaf stomata

CO 2 uptake in mesophyll cells Light reaction occurs O 2 produced stays here

C 4 Plants sugarcane In mesophyll: H 20 input light rxn O 2 ,

CAM Plants C-fixation and Calvin at different times of the day Avoiding evaporative loss

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Two Stages of Photosynthesis Light Reaction aka light dependent rxn Transforming light photons into ATP and the electron carrier NADPH Calvin Cycle aka light independent reaction Use ATP/NADPH to make glucose

The Calvin Cycle : C 3 carbon fixation In stroma of chloroplast Inputs CO 2 from air NADPH ATP from light rxn Output G 3 P: a 3 C organic molecule used to make glucose, fructose, starch, cellulose… e

The Calvin Cycle : C 3 carbon fixation 3 turns of the cycle Rubisco enzyme Ru. BP ATP Most G 3 P used to regenerate Ru. BP Energy input e- G 3 P one ‘extra’ G 3 P Energy stored

Calvin Cycle Accounting Per turn CO 2 1 Consume ATP 3 Consume NADPH 2 Produces G 3 P Produces Glucose Consume 3 turn 3 9 6 1 6 turns 6 18 12 2 1

http: //www. science. smith. edu/departments/Biology/Bio 231/calvin. ht ml http: //faculty. nl. edu/jste/calvin_cycle. htm http: //highered. mcgrawhill. com/sites/0070960526/student_view 0/chapter 5/animation_quiz _1. html http: //www. blinkx. com/watch-video/photosynthesis-bioflixanimation/z. WVQ 8 Ts. GQEG 7 FGsd 2 MWPTw http: //www. wiley. com/college/boyer/0470003790/animations/photo synthesis/photosynthesis. htm

This version of photosynthesis is used by 85% of plants - the C 3 plants include grains, soy, legumes, cotton, most trees, and more What about the other 15%? i. e. the C 4 and CAM plants Selection produces functional adaptations, but not necessarily at optimal efficiency 1

In hot, dry conditions, plant will undergo Photorespiration • to conserve water, leaf stomata close, preventing CO 2 intake and O 2 release. • as CO 2 concentration in the chloroplasts drops, Rubisco fixes oxygen instead of CO 2. • Photorespiration wastes radiant energy no glucose is made, no ATP is made What’s a plant to do?

CO 2 uptake in mesophyll cells Light reaction occurs O 2 produced stays here 4 C molecule – PEP - made C 4 Plants separate Cfixation and the Calvin cycle into different cells PEP shuttles CO 2 to bundle-sheath cells 4 C 3 C + CO 2 used in Calvin cycle Therefore can keep stomata closed 2

C 4 Plants sugarcane In mesophyll: H 20 input light rxn O 2 , PEP fixes C PEP yields CO 2 In bundle-sheath cells: Calvin cycle G 3 P sugar corn,

CAM Plants C-fixation and Calvin at different times of the day Avoiding evaporative loss • Stomates open at night • CO 2 is converted to an acid and stored hottest, driest conditions • During the day, the acid is broken down • CO 2 released to RUBISCO for photosynthesis CAM plants can ‘idle’ a while