photosynthesis/ cellular respiration

Topics: Photosynthesis, Cellular respiration, Adenosine triphosphate Pages: 3 (670 words) Published: April 13, 2014
Photosynthesis (happens in chloroplasts in mesophyll cells) 1. Light dependent stage
Happens in the grana of chloroplasts
Light (energy) gets trapped by chlorophyll pigments (light energy converted to chemical energy) This energy used to turn ADP and Pi into ATP
Energy used to split water (H2O) into Hydrogen and Oxygen
The hydrogen ions get collected by NADP, which becomes NADPH The Oxygen is waste, and leaves!
So, in this stage, water comes in.
ATP and NAPDH come out, as does Oxygen.

2. Light independent stage (Carbon Reduction)
Happens in the stroma of the chloroplast.
It’s the Calvin Cycle
At the start of the cycle, there’s a 5 Carbon molecule RuBP A CO2 molecule enters and attaches to it, making a 6 Carbon molecule Rubisco is the enzyme that makes this happen.
That’s not stable, so that 6C molecule splits into two 3C molecules (PGA) The PGA molecules are “reduced” by NADP to form PGAL
This takes energy; ATP turns back into ADP
PGAL, a 3C molecule, is a starting point for glucose (off to the cytosol…) Other PGALs are used to make RuBP, and it starts again…
If 6 CO2 come in, and get added to 6 RuBP, that makes 6 of the unstable 6C molecule. When that breaks down, you get 12 PGA molecules.
Those 12 PGA molecules, after NADPH and ATP do their thing, become 12 PGAL molecules. 2 of those PGALs go off to the cytosol to form glucose. (2x3C will make one 6C glucose) 10 of the PGALs (3C each remember = 30C) form 6 RuBP (5C molecules…6x5 =30!) So it takes 6CO2 coming in to end up with a glucose…

BUT, actually only one CO2 gets dealt with at a time, so it takes 6 turns of the cycle to end up with a glucose…

Briefly? CO2, NAPDH, ATP come in.
Glucose, NAPD, ADP come out.

Other stuff?
C3 plants are called that because carbon reduction begins with the 3C molecule PGA. C4 plants have a step before the Calvin cycle, where a step occurs in mesophyll cells to make a 4C compound. This compound gets transported to cells around vascular...
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