All Free Biology MCQs with Answers

4061. The phase of photosynthesis in which sugar is synthesized by reducing CO2 is also called as dark reaction because:

• A. It requires darkness
• B. It does not require light
• C. It requires night period
• D. It cannot proceed in light

Explanation: It is dark reaction which uses the assimilatory power and reducing power synthesized in light reaction in reducing CO2 to synthesize carbohydrates. It may occur in light as well as in dark.

4062. The reaction centre of photosystem have:

• A. One molecule of chlorophyll a and primary electron acceptor
• B. Many molecule of chlorophyll a and primary electron acceptor
• C. One or more molecules of chlorophyll a and primary electron acceptor
• D. Chlorophyll a, chlorophyll b and primary electron acceptor

Explanation: Reaction center of photosynthesis lies in chlorophyll a. It consists of one or more molecules of chlorophyll a along with a primary electron acceptor and associated electron carrier of electron transport system. Chlorophyll a molecules of reaction center and associated proteins are closely linked to the nearby electron transport system.

4063. Chlorophyll a molecules of reaction center and associated proteins are closely linked to the nearby electron transport system:

• A. Primary electron acceptor
• B. Chlorophyll b
• C. Accessory pigments
• D. Carotenoids

Explanation: Chlorophyll a molecules of reaction center and associated proteins are closely linked to the nearby electron transport system.

4064. The splitting up of water molecule into two hydrogen ions and an oxygen atom, by light is called:

• A. Electrolysis of water
• B. Ionization of water
• C. Photolysis of water
• D. Autolysis

Explanation: Photo means light and lysis means splitting up. So splitting up of water by light is called photolysis of water.

4065. The correct sequence of electron carriers which receive the electrons from primary electron acceptor of PS-II and pass it to PS-I:

• A. PS → Cytochrome complex → PQ
• B. PQ → PC → Cytochrome complex
• C. Cytochrome complex → PQ → PC
• D. PQ → Cytochrome complex → PC

Explanation: It is photosynthetic electron transport chain involved in non-cyclic phosphorylation.

4066. Pick up the one not involved in cyclic electron flow of light reaction of photosynthesis:

• A. PQ
• B. PC
• C. Cytochrome complex
• D. Fd

Explanation: Cyclic phosphorylation involves PS-I, primary electron acceptor of PS-I, Fd, cytochrome comple and PC.

4067. As electrons move down the photosynthetic electron transport chain their energy goes on decreasing and is used by thylakoid membrane to produce:

• A. ATP
• B. Water
• C. Oxygen
• D. NADH2

Explanation: It occurs through chemiosmosis in cytochrome complex.

4068. Pick up the correct flow of electrons in second electron transport chain of non-cyclic photophosphorylation:

• A. NADP → Primary electron acceptor of PS-I → NADP → PS-I
• B. PS-I → Fd → Primary acceptor of PS-I → NADP
• C. PS-I → Primary acceptor of PS-I → NADP → Fd
• D. PS-I → Primary acceptor of PS-I → Fd → NADP

Explanation: It starts from PS-I and ends at formation of reducing power.

4069. This pathway uses the photosystem-I, but not photosystem-II:

• A. Non-cyclic photophosphorylation
• B. Cyclic electron flow
• C. Z-scheme
• D. Non-cyclic electron flow

Explanation: In cyclic phosphorylation only PS-I is involved.

4070. The details of path of carbon in dark reaction of photosynthesis were discovered by Melvin, Calvin and his colleagues at:

• A. Oxford university
• B. University of California
• C. Cambridge university
• D. Tubingen university

Explanation: Melvin Calvin and his colleagues at The University of California discovered the details of path of carbon in these reactions. He was awarded Nobel prize in 1961.