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PHASE ONE: LIGHT-DEPENDENT REACTIONS Photosystem II (in thylakoid membrane) Light excites electrons Water is split into H+ and O2 o O2 leaves as waste o H+ stays inside of grana Passes electron on to Photosystem I Photosystem I (in thylakoid membrane) Light excites electrons Is constantly being feed electrons from photosytem II Electron is passed on to Ferrodoxin Ferrodoxin (in thylakoid membrane) Transfers electron to NADP+ NADP+ combine with H+ to form NADPH o This happens outside of the thylakoid membrane, in the stroma. o NADPH is a energy storing chemical used later in photosynthesis ATP Synthase The concentration of H+ builds up inside the grana. ATP Synthase opens a channel, and H+ rushes through the channel, through the thylakoid membrane, to the stroma. This converts ADP (adenosine di-phosphate) to ATP (adenosine tri-phosphate) o This happens in the stroma, outside of the thylakoid membrane PHASE TWO: LIGHT INDEPENDENT REACTIONS, CALVIN CYCLE Step 1 6 CO2 molecules from the atmosphere combine with 6 RuBP molecules o CO2 has 1 carbon: 6 X 1 = 6 total carbons o RuBP has 5 carbons: 6 X 5 = 30 total carbons o 30 + 6 = 36 This makes 12 molecules of 3-PGA o 3-PGA has 3 carbons: 12 X 3 = 36 total carbons Step 2 The 12 molecules of 3-PGA are converted to 12 molecules of G3P. Energy is required to do this. o It comes from 12 ATP molecules and 12 NADPH molecules. o They are reduced to 12 ADP molecules and 12 NADP+ molecules G3P also has 3 carbons: 12 X 3 = 36 Step 3 (Rubisco) The enzyme rubisco removes 2 molecules of G3P to be used to make sugars. The other 10 molecules of G3P are converted back into 6 molecules of RuBP. Starting: G3P: 12 X 3 = 36 carbons Ending: G3P: 2 X 3 = 6 carbons RuBP: 6 X 5 = 30 carbons 30 + 6 = 36