Photosynthesis in Higher Plants
Test 2

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which type of phosphorylation occurs only in Photosystem I?

Cyclic photophosphorylation
Non-cyclic photophosphorylation
Substrate-level phosphorylation
Oxidative phosphorylation
1

In cyclic photophosphorylation, electrons cycle within Photosystem I, producing ATP without NADPH or oxygen evolution.

Which of the following statements about photorespiration is correct?

It produces ATP
It occurs in C₄ plants
It reduces photosynthetic efficiency
It increases CO₂ fixation
3

Photorespiration reduces the efficiency of photosynthesis by consuming O₂ and releasing CO₂ without ATP synthesis.

Which of the following is a feature of the C4 pathway in plants?

It forms a three-carbon compound as the first stable product.
It is less efficient in hot and dry climates.
It involves spatial separation of carbon fixation and the Calvin cycle.
Stomata remain open throughout the day.
3

The C4 pathway separates carbon fixation in mesophyll cells and the Calvin cycle in bundle sheath cells.

Photorespiration occurs due to which of the following reasons?

Low oxygen concentration
High carbon dioxide concentration
The oxygenase activity of RuBisCO
Efficient carbon fixation
3

Photorespiration occurs when RuBisCO binds oxygen instead of carbon dioxide.

Which of the following statements about cyclic photophosphorylation is correct?

It produces both ATP and NADPH.
Electrons return to Photosystem I after energy transfer.
It results in the release of oxygen.
It only occurs in non-green tissues.
2

In cyclic photophosphorylation, electrons return to Photosystem I, producing only ATP.

Which molecule acts as the primary acceptor of CO2 in C4 plants?

RuBP (Ribulose-1,5-bisphosphate)
PEP (Phosphoenolpyruvate)
3-PGA (3-Phosphoglyceric acid)
Oxaloacetic acid
2

In C4 plants, PEP captures CO2, forming oxaloacetic acid.

Which of the following is a product of the light-independent reactions of photosynthesis?

Oxygen
ATP
Glucose
NADPH
3

Glucose is produced during the light-independent Calvin cycle using ATP and NADPH.

Which structure in C₄ plants prevents photorespiration?

Palisade mesophyll
Bundle sheath cells
Spongy mesophyll
Guard cells
2

In C₄ plants, bundle sheath cells contain RuBisCO and maintain high CO₂ concentration to prevent photorespiration.

What is the role of PEP carboxylase in C₄ plants?

Fixes CO₂ in mesophyll cells
Reduces NADP⁺ to NADPH
Synthesizes ATP
Breaks down starch
1

PEP carboxylase fixes CO₂ into oxaloacetic acid (OAA) in the mesophyll cells of C₄ plants.

Which factor is most limiting for photosynthesis under natural conditions?

Water
Temperature
Carbon dioxide
Oxygen
3

CO₂ is the most limiting factor for photosynthesis since its atmospheric concentration is very low (0.03-0.04%).

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