Biology Multiple Choice Questions on “Higher Plants Photosynthesis – Electron Transport”.
1. The electron transport system occurs in _____
a) Thylakoid membrane
b) Stroma
c) Cytosol
d) Mitochondria
Answer: a
Clarification: It is in the thylakoid membrane, in which the electron transport system occurs. Each thylakoid membrane is a closed compartment that gets protons from stroma by the b6 or f complex. Also, thylakoid membrane is impermeable to protons.
2. The first electron acceptor in photosystem 1 is _____
a) Plastoquinone
b) Cytochrome b
c) A Fe-S protein
d) Water
Answer: c
Clarification: The first electron acceptor in photosystem 1 is a Fe-S protein. It is a stable complex of iron and sulfur atoms bonded to a protein. It primarily accepts the electrons and passes onto NADP+.
3. Water produces electrons for the reduction reactions of photosynthesis.
a) True
b) False
Answer: a
Clarification: It is a true statement. The photolysis of water (2 molecules) produces four electrons that are required for the reduction reactions of photosynthesis which is needed for non-phosphorylation.
4. How much hydrogen protons are released by twelve water molecules?
a) 48
b) 6
c) 12
d) 24
Answer: d
Clarification: By understanding the photolysis equation, one water molecule gives 2 hydrogen protons. So, 12 water molecules will give 24 hydrogen protons.
5. The name of the scheme given to the transport of electrons is called as _______
a) Z scheme
b) W scheme
c) Y scheme
d) E scheme
Answer: a
Clarification: The scheme is called Z-scheme. This name was given due to the shape of the sequence. The transfer of electrons from PS II to NADP+ produces this scheme when the carries are placed in the order of the redox potential scale.
6. _____ is the only product in cyclic photophosphorylation.
a) ADP
b) ATP
c) Hydrogen
d) Oxygen
Answer: b
Clarification: ATP is the only product in cyclic photophosphorylation. PS II is not involved in this process. So, there will be no creation of reducing power i.e. NADPH + H+. And the only source of energy is ATP in cyclic photophosphorylation.
7. In PS II, the last electron acceptor is ______
a) Plastocyanin
b) Ferredoxin
c) Cytochrome b6
d) Cytochrome b12
Answer: a
Clarification: Plastocyanin, which is a Cu protein is the last electron acceptor in PS II. It receives the electrons from cytochrome f and passes onto PS I. This is all based on non-cyclic photophosphorylation reaction.
8. _______ accepts the electrons from Pheophytin.
a) Cytochrome f
b) Cytochrome d
c) Plastoquinone
d) Ferredoxin
Answer: c
Clarification: Plastoquinone (PQ) is an electron carrier. It accepts the electrons from pheophytin. PQ gets 2 electrons and passes these to cytochrome b6. It also plays a major role in light-dependent reactions.
9. The electrons produced in the photolysis of water enters ______
a) Fe-S protein
b) PS II
c) Plastocyanin
d) Cytochrome a
Answer: b
Clarification: During the photolysis of water, two electrons are produced. These electrons enter into PS II and it transfers the electron to Pheophytin (the primary electron acceptor). These electrons mainly help during reduction reactions.
10. The process by which the pH gradient across the membrane provides energy for the synthesis of ATP is called as ______
a) Phosphorylation
b) Transfusion
c) Diffusion
d) Chemiosmosis
Answer: d
Clarification: There is a pH gradient across the thylakoid membrane, which provides a proton motive force. This creates chemical potential energy for the production of ATP from ADP and inorganic phosphate is called chemiosmosis. Peter Mitchell proposed this theory.
11. In which process does carbon dioxide join photosynthesis?
a) Oxidation
b) PS I
c) Dark reaction
d) Reduction
Answer: c
Clarification: Carbon dioxide is entering the photosynthetic pathway through dark reaction. RuBP reacts with CO2 to form the first unstable carbon compound. So, here 6 molecules of CO2 are required to start dark reaction.