Question

1a.Photosynthesis creates glyceraldehyde 3 phosphate” is a more accurate statement than “Photosynthesis creates glucose.” Explain

1b.The Calvin cycle couldn’t occur without the light reaction. What does the light reaction provide that the Calvin cycle needs?

Answer 1

1) A) Glyceraldehyde 3-phosphate (G3P) is a 3-carbon sugar and it is the product of the Calvin cycle. Glyceraldehyde 3-phosphate is the starting point for the synthesis of glucose, sucrose, starch and other carbohydrates. Some of this G3P is used to regenerate the RuBP and it is very crucial for the continuation of the cycle, but some is available for molecular synthesis to make fructose diphosphate. This fructose diphosphate is then used to make glucose, starch, sucrose, and other carbohydrates. Organic molecule such as glucose is made in the cytoplasm from the products of the Calvin cycle. For this reason, it is accurate to say that photosynthesis creates glyceraldehyde 3 phosphate instead of glucose.

1) B) The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle. The ATP is responsible to provide the energy, and the NADPH is responsible to supply the electrons to the Calvin cycle.