Photosynthesis: Dark Reactions Ms. Bush, Ms. Cohen Plants and Photosynthesis Unit

Photosynthesis Overview What is the chemical equation for photosynthesis? _____ + ______ _____ + _______

Calvin Cycle (light - Independent cycle) The Calvin cycle uses ATP and NADPH to produce high energy sugars.

ATP and NADPH power sugar synthesis in the Calvin Cycle. Occurs in the stroma of the chloroplast. For every two turns of the Calvin Cycle one glucose molecule is formed. Total input needed: 6CO 2 and many ATP and NADPH molecules. 4

Light Reactions Summary Light activates P680 and excites an electron in Photosystem II. Water is split to produce oxygen and to replace the lost electron. The excited electron goes through the electron transport chain creating ATP. Light then activates P700 so that an electron is excited in Photosystem I. This electron travels through a short electron transport chain to produce NADPH.

Dark Reactions Summary CO 2 enters the cycle and is fixed (attached to six 5- carbon molecules) by the enzyme Rubisco. The result is twelve 3-carbon molecules. The twelve 3-carbon molecules are converted to higher energy forms by input of ATP and NADH. Two of the twelve 3-carbon molecules are removed from the cycle to be converted to sugars and other compounds. The remaining ten 3-carbon molecules are converted back to six 5-carbon molecules thus restarting the cycle.