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

About 50% of all sunlight absorbed

Answer

Exactly 10% in all plants

Answer

100% in C4 plants

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

It converts excess light into extra ATP

Answer

It speeds up the Calvin cycle

Answer

It increases water splitting

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

It synthesizes new RuBisCO protein

Answer

It transfers electrons to RuBisCO

Answer

It phosphorylates RuBP for use in the Calvin cycle

Question 4

How does drought stress affect photosynthesis?

Accepted Answer

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

Answer

Drought increases photosynthesis by concentrating leaf solutes

Answer

Drought has no effect because water is not a reactant in the Calvin cycle

Answer

Drought speeds up light reactions but slows the Calvin cycle

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 regeneration only affects the light reactions

Answer

RuBP is stored when not needed and does not affect the rate

Answer

RuBP is regenerated automatically without ATP

Question 6

How does leaf age affect photosynthetic capacity?

Accepted Answer

Young mature leaves photosynthesize most rapidly; very young and old leaves have lower rates

Answer

Old leaves always photosynthesize fastest

Answer

Photosynthetic rate is constant throughout leaf life

Answer

Young leaves have no chlorophyll and cannot photosynthesize