Photosynthesis: Carbon Reactions Calvin Cycle

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17 Questions

Which phase of the Calvin cycle involves the formation of two molecules of 3-phosphoglycerate?


What is the main purpose of the dark reactions in photosynthesis?

Reduce CO2 to carbohydrate

Which enzyme catalyzes the carboxylation of ribulose-1,5-bisphosphate in the Calvin cycle?


What is the primary factor that directly regulates the stroma reactions in photosynthesis?


How many stages are involved in the Calvin cycle?

Three stages

What proportion of triose phosphate is typically used for sucrose or starch production in the Calvin cycle?


What is the main reason why the forward reaction of the carboxylation of ribulose-1,5-bisphosphate is strongly favored?

Low concentration of CO2 in photosynthetic cells

What enzyme represents up to 40% of the total soluble protein in most leaves?


What regulates the Calvin cycle through light-dependent enzyme activation?

Ribulose-5-phosphate kinase

What factor determines the balance between the Calvin cycle and the C2 oxidative photosynthetic carbon cycle?

The concentrations of the substrates CO2 and O2

What is calculated to be about 4 mM within the chloroplast stroma?

Concentration of rubisco active sites

What happens to the concentration of CO2 in a solution in equilibrium with air as the temperature increases?

Decreases more than O2

How does the concentration ratio of CO2 to O2 change as the temperature rises?


What effect does increasing temperatures have on photorespiration and photosynthesis?

Increases relative to photosynthesis

What is the impact of rubisco's kinetic properties at higher temperatures?

Enhances relative increase in oxygenation

Why is it difficult to measure the rate of photorespiration in intact cells?

Because it is concurrent with photosynthesis

How much carbon entering the C2 oxidative photosynthetic carbon cycle is theoretically released as CO2?


This quiz covers the process of carbon reactions in the Calvin Cycle of photosynthesis, including the reduction of CO2 to carbohydrate in the stroma of chloroplasts. It also explores how these reactions are coupled with the generation of ATP and NADPH in the thylakoid membrane.

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