BioInteractive Regulation and Efficiency of Photosynthesis 2

Question 1

What is the overall efficiency of photosynthesis in converting solar energy to glucose?

Accepted Answer

Typically 1–3% under natural conditions

Answer

Plants typically convert only 1–3% of incident solar energy into chemical energy in glucose under field conditions, due to reflection, heat loss, and metabolic inefficiencies.

Question 2

How does non-photochemical quenching (NPQ) protect plants from excess light?

Accepted Answer

It dissipates excess excitation energy as heat to prevent photo-oxidative damage

Answer

NPQ is a photoprotective mechanism where carotenoids and other components harmlessly dissipate excess absorbed light energy as heat, preventing damage to the photosystems.

Question 3

What is the role of RuBisCO activase in photosynthesis?

Accepted Answer

It reactivates RuBisCO by removing inhibitory sugar phosphates from its active site

Answer

RuBisCO activase uses ATP to remove inhibitors (like RuBP and other sugar phosphates) from the active site of RuBisCO, keeping it functional in the light.

Question 4

How does drought stress affect photosynthesis?

Accepted Answer

Stomata close to conserve water, reducing CO2 entry and thus photosynthesis

Answer

Under drought, stomata close to prevent water loss, but this simultaneously limits CO2 diffusion into the leaf, reducing Calvin cycle activity and overall photosynthesis.

Question 5

What is the significance of the RuBP regeneration step in the Calvin cycle for maintaining photosynthetic rate?

Accepted Answer

If RuBP is not regenerated, the Calvin cycle stops and CO2 cannot be fixed

Answer

RuBP must be continuously regenerated from 3-carbon intermediates using ATP and NADPH; without regeneration, the substrate for CO2 fixation is depleted and photosynthesis ceases.

BioInteractive - Photosynthesis BioInteractive Test Practice Test

BioInteractive - Photosynthesis BioInteractive Test Practice Test

BioInteractive Regulation and Efficiency of Photosynthesis 2