Pentose Phosphate Shunt Need reducing power - NADPH Need pentose sugars - RNA & DNA Title slide

The pathway - hexose monophosphate shunt, or pentose phosphate pathway.

The glucose 6-phosphate dehydrogenase reaction; the first reaction in the pathway. Make NADPH.

Phosphogluconate dehydrogenase Phosphogluconate dehydrogenase. The second reaction in the pathway also makes NADPH. There is a release of carbon dioxide that makes the reaction irreversible.

Ribulose 5-phopshate isomerase reaction gives R5P Ribulose 5-phopshate isomerase reaction gives R5P. Ribulose 5-phosphate epimerase reaction gives Xu5P.

The transketolase reaction uses TPP as coenzyme to stabilize the carbanion.

Transaldolase contains a lys residue that forms a Schiff base with S7P to facilitate the aldol cleavage reaction.

The carbon-carbon bond formations and cleavages that convert three C5 sugars to two C6 and one C3 sugar.

Photosynthesis Dark reaction - carbon fixation Title slide

The Calvin cycle. The number of lines in an arrow indicates the number of molecules reacting in that step for a single turn of the cycle that converts three CO2 molecules to one GAP molecule.

The time course levels of 3PG (purple) and RuBP (green) in steady state during which carbon dioxide is removed. The 3PG disappears because it is used in the reactions of the Calvin cycle. RuBP accumulates because it can’t be used to fix carbon dioxide.

Rubisco structure.

A reaction mechanism for rubisco.

Light activation of FBPase and SBPase.

Probable mechanism of the oxygenase reaction of rubisco, a competing reaction

The C4 pathway.

The photorespiration pathway.