Question

Choose the correct answer from the alternatives given.
The first event in the Calvin cycle is the attachment of carbon dioxide to the five-carbon RuBP molecule, which

• A. forms a six-carbon molecule that immediately breaks down into two three-carbon PGA molecules
• B. is a reaction assisted by large quantities of RuBP carboxylase enzyme
• C. decreases cell carbon dioxide levels, which increases the diffusion gradient
• D. all of the above

Answer 1

The correct option is D all of the above

The first stage of the Calvin cycle incorporates carbon from CO2 into an organic molecule, a process called carbon fixation. In plants, atmospheric CO2 enters the mesophyll layer of leaves by passing through pores on the leaf surface called stomata. It can then diffuse into mesophyll cells, and into the stroma of chloroplasts, where the Calvin cycle takes place. an enzyme nicknamed rubisco (RuBP carboxylase-oxygenase) catalyzes attachment of CO2 to a five-carbon sugar called ribulose bisphosphate (RuBP). The resulting 6-carbon molecule is unstable, however, and quickly splits into two molecules of a three-carbon compound called 3-phosphoglycerate (3-PGA).

So, the correct option 'all of the above'.