Question

Which of the following does NOT happen in the Calvin cycle of photosynthesis?A. hydrolysis of ATP to ADP B. the incorporation of CO2 into an organic molecule by RUBISCO C. the synthesis of a three-carbon carbohydrate D. reduction of NADP+ to NADPH

Answer 1

The correct answer is: A. hydrolysis of ATP to ADP

This step occurs in the light-dependent phase of photosynthesis.

Calvin cycle is the second phase of photosynthesis also called light-independent reactions (no light required for this step). This process occurs in in the stroma (the inner space of chloroplasts) and during it three-carbon sugars are produced from CO2. Calvin cycle can be divided into three steps:

1. Carbon fixation where CO2 from the air is “apsorbed” by plants and combined with a five-carbon acceptor molecule, ribulose-1,5-bisphosphate (RuBP). Formed molecule with 6 C atoms is then split into two 3-phosphoglyceric acid (3-PGA) molecules by the enzyme rubisco.

2. Reduction refers to conversion of 3-PGA to glyceraldehyde-3-phosphate (G3P), sugar that can be used in further steps of photosynthesis. NADP+ is reduced to NADPH.

3. Regeneration refers to recycle of some G3P in order to regenerate the RuBP acceptor for the carbon fixation.