All Free Biology MCQs with Answers

3521. What is the color of Chlorophyll-a molecules?

• A. Bluish green
• B. Yellowish green
• C. Dark green
• D. Reddish green

Explanation: Bluish green - Correct. Chlorophyll-a absorbs red and blue light, reflecting a bluish-green color.

3522. Which of the following is NOT an event of light-dependent reactions during photosynthesis?

• A. Photolysis of water
• B. Production of ATP by photophosphorylation
• C. Reduction of Carbon dioxide
• D. Reduction of NADP to NADPH

Explanation: Reduction of Carbon dioxide - Correct. Carbon dioxide reduction occurs in the Calvin cycle, which is part of the light-independent reactions, not the light-dependent stage.

3523. Which one of the following is the direct source of energy in living bodies?

• A. ATP
• B. Glucose
• C. Amino acid
• D. Fatty acid

Explanation: The direct source of energy in living bodies is ATP (Adenosine Triphosphate). It stores energy in phosphate bonds, releasing it when broken down to fuel cellular processes.

3524. In chlorophyll a, a -CH₃ group is attached to which pyrrole ring?

• A. 1st
• B. 2nd
• C. 3rd
• D. 4th

Explanation: 1st - Correct. In chlorophyll a, a methyl (-CH₃) group is attached to the first pyrrole ring, distinguishing it from chlorophyll b, which has a formyl (-CHO) group instead.

3525. Net ATP produced at the end of glycolysis:

• A. 2 ATP
• B. 4 ATP
• C. 6 ATP
• D. 3 ATP
• E. 8 ATP

Explanation: One glucose molecule yields four ATP molecules in total during glycolysis. Since 2 ATP molecules are used up in the first phase of glycolysis, there is a net gain of 2 ATP molecules.

3526. Pyruvic acid is acid of:

• A. 4 carbon compound
• B. 5 carbon compound
• C. 6 carbon compound
• D. 3 carbon compound

Explanation: The correct answer is E 3-carbon compound. Pyruvic acid is a three-carbon compound. It is an important intermediate product in the process of glycolysis, which is the initial step of cellular respiration. During glycolysis, glucose, a six-carbon compound, is broken down into two molecules of pyruvic acid. Each pyruvic acid molecule contains three carbons.

3527. The common energy currency of the cell is:

• A. NHDP
• B. ADP
• C. ATP
• D. NADH

Explanation: ATP stands for adenosine triphosphate, which is a molecule that serves as the primary energy currency in living organisms. It is often referred to as the "energy currency" because it stores and releases energy as needed for cellular processes. Therefore option C is correct.

3528. Light reaction of photosynthesis takes place in:

• A. Cristae
• B. Stroma
• C. Cisternae
• D. Thylakoid

Explanation: Light reaction of photosynthesis takes place in the thylakoid membrane consisting of grana within it. So option D is the correct answer.

3529. Each carrier in the electron transport chain is first _ and then _.

• A. Broken-down, Regenerate
• B. Generated, Broken-down
• C. Oxidized, Reduced
• D. Reduced, Oxidized

Explanation: In the electron transport chain, the carriers are responsible for shuttling electrons from one component to another. They first accept electrons, which results in their reduction (gain of electrons), and then pass those electrons along to the next carrier, which leads to their oxidation (loss of electrons). This process of sequential reduction and oxidation reactions is essential for the transfer of energy and the generation of ATP in cellular respiration. The electrons are eventually passed to the final electron acceptor, which is typically oxygen, and are used in the production of water.

3530. Electron transport chain explains:

• A. Photophosphorylation
• B. Z-Scheme
• C. Photolysis
• D. Mechanism of ATP synthesis

Explanation: The electron transport chain is a key component in the mechanism of ATP synthesis. During oxidative phosphorylation, which is the final stage of cellular respiration, the electron transport chain creates a proton gradient across the inner mitochondrial membrane. This gradient drives the synthesis of ATP through the action of ATP synthase.