All Free Biology MCQs with Answers

3541. The element whose electrons are excited during light reactions of photosynthesis is _.

• A. Carbon
• B. Hydrogen
• C. Magnesium
• D. Nitrogen

Explanation: Magnesium has two electrons in its outer shell, so it has a tendency to lose them. When light falls on chlorophyll, the two electrons of magnesium are excited, and they jump to a higher state where the primary electron acceptor absorbs them. Hence, option C is the correct option.

3542. Maximum photosynthesis can occur when:

• A. Blue light is given to the plant
• B. Red light is given to the plant
• C. Green light is given to the plant
• D. Yellow light is given to the plant

Explanation: Red light is more effective in photosynthesis because both the photosystems absorb light of wavelengths between 680 and 700 nm, respectively. So, option B is correct.

3543. What is the number of hydrogen atoms in the molecular formula of Chlorophyll-a?

• A. Six
• B. Fifty five
• C. Seventy
• D. Seventy two

Explanation: Molecular formula of Chlorophyll-a is C₅₅H₇₂O₅N₄Mg.Hence, option D is correct because the number of hydrogen atoms in the molecular formula of Chlorophyll-a are seventy-two.

3544. Oxygen, which is the last electron acceptor in electron transport chain is:

• A. Active
• B. At high energy level
• C. At low energy level
• D. Gets chemically deativated after electronic transfer

Explanation: Oxygen has high affinity for electrons which make it ideal to accept electrons so it is at low energy level so that it will accept more and more electrons and its behaviour remain idealSo, option C is accurate.

3545. Which of the following is not essential for photosynthesis?

• A. Oxygen
• B. Chlorophyll
• C. ATP
• D. Light

Explanation: Oxygen is a chemical element (symbol O) essential for life on Earth. It is a colorless, odorless gas that makes up about 21% of the Earth's atmosphere. Oxygen is crucial for cellular respiration in most organisms, allowing them to produce energy by converting glucose and other nutrients. It also plays a key role in combustion and is involved in various chemical reactions.

3546. Plants oxidize sugar in chloroplasts during the day without production of energy. This process is called:

• A. Photorespiration
• B. Oxidative phosphorylation
• C. Non-cyclic photophosphorylation
• D. Cyclic oxidative phosphorylation

Explanation: The process you're describing is called photorespiration. During photorespiration, plants take up oxygen and release carbon dioxide, which occurs in chloroplasts when the enzyme RuBisCO reacts with oxygen instead of carbon dioxide. This process can lead to the oxidation of sugar, but it does not produce energy in the way that cellular respiration does.

3547. Which reaction is also known as Z-scheme?

• A. Oxidative phosphorylation
• B. Cyclic photophosphorylation-
• C. Non-cyclic oxidative phosphorylation
• D. Non-cyclic photephosphorylation

Explanation: Non-cyclic photophosphorylation is often illustrated using the Z-scheme model. This model represents the linear flow of electrons during the light-dependent reactions of photosynthesis.

3548. Which of the pigments are common in both humans and plants?

• A. Carotenoids
• B. Fucoxanthin
• C. Xanthophyll
• D. Chlorophyll

Explanation: Carotenoids are found in both plants and human.In plants,carotenoids play a role in photosynthesis by absorbing light, while inhumans, they act as precursors to vitamin A and have antioxidant properties.

3549. In the Calvin cycle, CO2 reacts with RuBP to produce _.

• A. 3-PGA
• B. G3P
• C. 6-Carbon unstable intermediate
• D. 1,3 bisphosphoglycerate

Explanation: The reaction in the Calvin cycle where CO₂ reacts with RuBP produces a 6-carbon unstable intermediate because of the way carbon fixation occurs during the process.

3550. Which option is correct about a chlorophyll a molecule?

• A. Chemical formula C55H70O6N4Mg
• B. Porphyrin ring with nitrogen in centre
• C. Methyl group on second pyrrole ring
• D. Aldehyde group on second pyrrole ring

Explanation: The statement "Methyl group on the second pyrrole ring" in the context of chlorophyll a is correct.The presence of a methyl group on the second pyrrole ring is a correct part of the chlorophyll structure and plays a role in its overall function in photosynthesis.