The Light Reaction:
The light reaction occurs in the Thylakoid membrane. It is light dependent. In the membrane is a PS2 (photon system), a PS1, and an ATP Synthase. Energy from the photon hits the reaction center in the PS2. The reaction center is where the electrons are kept. The photon excites one of the electrons, which starts it's journey through the membrane. The electron travels to the PS1 and releases enough energy to actively transport an H+ ion across the membrane into the lumen. In the lumen there is a high concentration of H+ ions, which will be sent through the ATP Synthase to turn it and create ATP. The electron will release all it's energy, and then end up at the PS1. At the PS1 an electron will have just been excited by a photon, and the old electron (from the PS2) will need to replace the one that just left. The electron that just left will be sent to release it's energy. However, instead of using the energy to pump an H+ ion across the membrane, all the energy will be caught before it's released, and put into a NADP+, which will become a NADPH.
You are probably wondering how the electron that was in the PS2 is replaced. Part of the PS2 is a place where the oxidation of water occurs. The water is oxidized into Oxygen, Hydrogen protons, and electrons. The electrons go wait in the PS2, and the Oxygen is a byproduct of the Light Reaction.
Inputs
-water
-light energy (photons)
Outputs
-oxygen
-NADPH
-ATP
The Calvin Cycle:
The Calvin Cycle can be tricky to understand, but the best way to wrap your mind around it is to count Carbons.
Three molecules of CO2 are enter the cycle, and by the help of Rubisco, each carbon joins with a 5 carbon RuBP already in the cycle. Now we have 18 carbons, or 3 six carbon molecules. The six carbon molecules are really unstable so they immediately split into 6 three carbon molecules. These 6 three carbon molecules are going to be re-arranged. Each three carbon molecule is going to receive energy from 1 ATP and 1 NADPH during re-arrangement. That means 6 ATP and 6 NADPH are being used in all. During re-arrangement one 3 carbon molecule will be released from the cycle as a PGAL. Then 3 more ATP will help the other 15 carbons become 3 five carbon RuBP, again. Thus the cycle starts again.
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Inputs:
-3 CO2 (initial input)
-9 ATP (from the light reaction)
-6 NADPH (from the light reaction)
Outputs:
-1 PGAL
-9 ADP
-6 NADP+
As you can see Photosynthesis is amazing. Plants don't waste anything, and they produce oxygen. It doesn't get much better then that. I wish we were as efficient as plants, they rock!
The Calvin Cycle:
The Calvin Cycle can be tricky to understand, but the best way to wrap your mind around it is to count Carbons.
Three molecules of CO2 are enter the cycle, and by the help of Rubisco, each carbon joins with a 5 carbon RuBP already in the cycle. Now we have 18 carbons, or 3 six carbon molecules. The six carbon molecules are really unstable so they immediately split into 6 three carbon molecules. These 6 three carbon molecules are going to be re-arranged. Each three carbon molecule is going to receive energy from 1 ATP and 1 NADPH during re-arrangement. That means 6 ATP and 6 NADPH are being used in all. During re-arrangement one 3 carbon molecule will be released from the cycle as a PGAL. Then 3 more ATP will help the other 15 carbons become 3 five carbon RuBP, again. Thus the cycle starts again.
Learn how to draw cartoons, comics, and anime at Sketchfu!
Inputs:
-3 CO2 (initial input)
-9 ATP (from the light reaction)
-6 NADPH (from the light reaction)
Outputs:
-1 PGAL
-9 ADP
-6 NADP+
As you can see Photosynthesis is amazing. Plants don't waste anything, and they produce oxygen. It doesn't get much better then that. I wish we were as efficient as plants, they rock!
