All Free Biology MCQs with Answers

3401. The glycine generated during photorespiration enters?

• A. Glyoxysomes
• B. Mitochondria
• C. Peroxisomes
• D. Ribosomes

Explanation: Glycine generated during photorespiration is converted to serine, in the mitochondria which liberates CO2 and ammonia and leads to the reduction of NAD+ to NADH.

3402. How many ATP molecules are made from one glucose molecule during anaerobic cellular respiration?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Without oxygen, organisms must use anaerobic respiration to produce ATP, and this process produces only two molecules of ATP per molecule of glucose.

3403. Van Niel studied photosynthesis in:

• A. Protists
• B. Algae
• C. Fungi
• D. Bacteria

Explanation: In 1931, Van Neil studied the process of photosynthesis in bacteria, particularly sulfur bacteria and green sulfur bacteria. He was the first person to understand the science behind the process by which plants convert light into energy. He also demonstrated that the oxygen released by plants comes from the splitting of water, not carbon dioxide (Van Neil's Hypothesis).

3404. Enzymes for the light-dependent reactions are present in:

• A. Mitochondria
• B. Thylakoid membrane of the chloroplast
• C. Stroma of the chloroplast
• D. Cytoplasm of the cell

Explanation: The light-dependent reactions of photosynthesis take place within the thylakoids. These reactions occur when the pigment chlorophyll, located within the thylakoid membranes, captures energy from the sun (photons) to initiate the breakdown of water molecules.

3405. Where does oxygen come from in photosynthesis?

• A. Hydrogen sulphide
• B. Carbon dioxide
• C. Water
• D. Hydrogen peroxide

Explanation: In photosynthesis, photosystem II loses its electrons when excited by photons. To fill the electron 'gaps', water is split into oxygen, hydrogen ions and electrons by photons via a process called photolysis. The oxygen is released as a by-product.

3406. Which of the following gains electrons at the end of oxidative phosphorylation?

• A. Oxygen
• B. Carbon
• C. Hyrogen
• D. None of these

Explanation: Oxidative phosphorylation involves the release of energy in the form of ATP when reduced coenzymes (NADH, FADH2) pass through a series of electron carriers to get oxidized and lose their electrons to a final electron acceptor i.e. oxygen, which is reduced to form water.

3407. When NADH gives electron to oxygen, the number of ATP molecules produced are:

• A. 2
• B. 3
• C. 4
• D. 1

Explanation: In oxidative phosphorylation, the oxidation or loss of electrons by NADH yields three ATP molecules.

3408. Hexokinase is used in:

• A. Calvin Cycle
• B. Glycolysis
• C. Kreb's Cycle
• D. None of these

Explanation: Hexokinase is an enzyme used in the phosphorylation of glucose during the first step of glycolysis. This enzyme catalyzes the conversion of glucose to glucose-6-phosphate. The reaction involves the transfer of a phosphate group from ATP to glucose, resulting in the formation of glucose-6-phosphate.

3409. (Glucose)C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. The reaction mentioned above is:

• A. Aerobic respiration
• B. Photosynthesis
• C. None of these
• D. Anaerobic respiration

Explanation: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy is the equation of aerobic respiration. Aerobic respiration is the process by which cells generate energy (in the form of ATP) in the presence of oxygen. It is the most efficient way for cells to extract energy from organic molecules.

3410. In glycolysis, glycerate-1,3-bisphosphate is converted into glycerate-3-phosphate by losing _ phosphate molecules.

• A. 3
• B. 2
• C. 1
• D. 4

Explanation: In glycolysis, the conversion of glycerate-1,3-bisphosphate to glycerate-3-phosphate involves the loss of one phosphate molecule. The specific enzyme catalyzing this reaction is phosphoglycerate kinase.