Photosynthesis Flashcards
Phosphorylation
light energy is converted by an organism’s photosystems to ATP phosphate bond energy
(light energy boost being used to drive synthesis of ATP)
Calvin Cycle
importation of CO2 into a carbohydrate (in the stroma) by a eukaryotic photosynthesizing organism
3CO2 + 6NADPH + 9ATP –>
glyceraldehyde-3-phosphate + 6NADP+ + 9ADP + 8Pi
- this is whole equation doubled for a hexose molecule!
Three phases of the calvin cycle
- Carbon Fixation
- Reduction
- Regeneration
Carbon Fixation
the mechanism by which inorganic CO2 is incorporated into organic molecules
- carboxylation of ribulose-1,5-bp to form 2 glycerinate-3-p
Carboxylation in carbon fixation
carboxylates ribulose-1,5-bisphosphate into two glyerate-3-p molecules
C3 plants
plants that produce glycerinate-3-p as the first stable product of photosynthesis
Major regulatory enzyme in carboxylation
rubisco
Reduction
glycerate-3-p is phosphorylated by ATP to form glycerate-1,3-BP
this glycerinate-1,3-BP is then reduced by NADPH to form glyceraldehyde-3-P
Regeneration
the production of three ribulose-1,5-bisphosphate at the expense of five of the six glyceraldehyde-3-p molecules also at the expense of 3 ATP molecules
examples of light activated reactions (direct)
ribulose-1,5-bisphosphate carboxylase
NADP+-glyceraldehyde dehydrogenase
examples of light deactivated reactions (direct)
phosphofructokinase
glucose-6-P dehydrogenase
indirect mechanisms
pH: during the light rxn, protons are pumped out of stroma and increases the pH
Mg2+: light increases the stromal concentration of MG2+, which is required for activity of some enzymes
Ribulose-1,5-bisphosphate carboxylase enzyme
genes encoding for this are located in the chlorophast (L subunit) and the nucleus (S subunit) & are activated by light intensity to form L8S8 holoenzymes in the chloroplast
