Question

Detailed descriptions of what happens to the carbon atom: during photosynthesis (the light-dependent reactions and the light-independent reactions)transitioning between photosynthesis and respirationduring cellular respiration or fermentation

Answer 1

Carbon atoms have nothing to do with the light reactions. CO2 enters in the carbon reactions, enters the Calvin cycle and using 3 CO2, one molecule of glyceraldehyde-3-phosphate (G3P) is fixed. This G3P combines with other G3P and eventually turns into sucrose. Sucrose is split into fructose and glucose right before entering glycolysis. During glycolysis, glucose is split into two parts and results in two molecules of pyruvate. Pyruvate with then go to the Krebs cycle (if oxygen is present) or to fermentation (if oxygen is lacking). In fermentation pyruvate turns into either lactate or ethanol. In the Krebs cycle, pyruvate is decarboxylated to Acetyl CoA, then Acetyl CoA attaches to Oxaloacetate. This is also decarboxylated and CO2 leaves the system. CO2 does not enter the electron transport chain.

Answer 2

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