Photosynthesis Energy Conversion 3

Question 1

What is the quantum yield of photosynthesis and why is it important?

Accepted Answer

The ratio of photons absorbed to O2 released, measuring efficiency

Answer

The number of CO2 molecules fixed per day

Answer

The rate of ATP production per minute

Answer

The amount of glucose stored per leaf

Question 2

In the Z-scheme, electrons ultimately flow from which molecule to which molecule?

Accepted Answer

H2O → NADP+

Answer

NADPH → H2O

Answer

CO2 → glucose

Answer

ATP → ADP

Question 3

Why does the Calvin cycle require more ATP than NADPH on a per-CO2 basis?

Accepted Answer

Because the regeneration of RuBP requires extra ATP beyond what's needed for G3P reduction

Answer

Because CO2 fixation itself consumes ATP

Answer

Because NADPH is recycled but ATP is not

Answer

Because photorespiration destroys extra NADPH

Question 4

Which pigment extends light absorption into wavelengths that chlorophyll a cannot efficiently capture?

Accepted Answer

Carotenoids (β-carotene and xanthophylls)

Answer

Phytochrome

Answer

Cryptochrome

Answer

Phycoerythrin (in land plants)

Question 5

What happens to the energy of a photon that is absorbed by an antenna pigment but NOT transferred to the reaction center?

Accepted Answer

It is re-emitted as fluorescence or dissipated as heat

Answer

It is stored as ATP

Answer

It splits a water molecule directly

Answer

It converts CO2 to glucose

Question 6

What is the significance of P700 absorbing longer-wavelength light than P680?

Accepted Answer

P700 electrons are at a lower redox potential and can reduce ferredoxin

Answer

P700 generates more ATP per photon

Answer

P700 directly oxidizes water

Answer

P700 converts light energy into heat

Question 7

How do inhibitors like DCMU (diuron) reveal the electron transport pathway in thylakoids?

Accepted Answer

By blocking plastoquinone binding in PSII, halting electron flow from PSII to PSI

Answer

By blocking rubisco and stopping CO2 fixation

Answer

By preventing ADP phosphorylation in ATP synthase

Answer

By inhibiting ferredoxin-NADP+ reductase