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.
