6 2 Calvin Cycle the second biochemical pathway

6 -2 Calvin Cycle the second biochemical pathway

Carbon Fixation by the Calvin Cycle Carbon atoms from CO 2 are bonded or “fixed” into organic compounds. 3 steps occur in the stroma of chloroplasts. • requires CO 2, NADPH and ATP • Carbon from carbon dioxide are bonded or "fixed" into organic compounds • takes place in the stroma of the chloroplast • end products are PGAL (which can be converted to organic molecules where energy is stored), ADP, NADP, & oxygen • Called dark reactions since light is not needed

Alternative Pathways Modes of Calvin Cycle C 3 plants - fix carbon dioxide in the Calvin cycle (most common) C 4 plants (corn, sugar cane, crab grass) -can close stomata in extreme heat, thereby allowing less CO 2. fix carbon dioxide using an enzyme before the Calvin cycle. CAM plants (cactus, pineapple) - fix carbon dioxide at night when stomata (pores on underside of leaves) open without water loss

Rate of Photosynthesis depends on the environment 1. Light intensity - as light intensity photosynthesis until it plateaus increases, so does 2. Carbon dioxide levels - as carbon dioxide increases, so does photosynthesis until it plateaus 3. Temperature - as temperature increases, photosynthesis increases to a certain temperature, then the rate of photosynthesis decreases

Photosynthesis overall equation_______________ Step Where does Starting End product(s) it occur? substance(s

overall equation carbon dioxide + water + energy → oxygen + organic molecules Step Where does it occur? Starting substance(s) End product(s) 1. electron transport Thylakoid membrane of chloroplast Light energy NADPH & ATP & water 2. Calvin cycle Stroma of chloroplast Carbon dioxide, NADPH & ATP Oxygen PGAL ADP NADP

Section 6 -2 Review 1. In what part of the chloroplast does the Calvin cycle take place? 2. Describe what can happen to PGAL molecules made in the Calvin cycle. 3. How many turns of the Calvin cycle are needed to produce a molecule of PGAL? How many molecules of ATP and NADPH are used in the process? 4. What plant structures control the passage of water out of a plant and carbon dioxide into a plant? 5. What is a C 4 plant?