All Free Biology MCQs with Answers

1461. Active transport is dependent on____________?

• A. Photosynthesis
• B. Respiration
• C. Photophosporylation
• D. None of these

Explanation: Active transport requires ATP to move substances against their concentration or electrochemical gradients, and plant cells mainly obtain this ATP through cellular respiration. Students may choose a because photosynthesis supplies energy-rich products in plants, but respiration is the immediate process that generates ATP for transport.

1462. Which of the following promotes growth in plants?

• A. Photorespiration
• B. Calvin cycle
• C. Both of these
• D. None of these

Explanation: The Calvin cycle fixes carbon dioxide into organic compounds that can be used to form sugars and other substances needed for plant growth. Photorespiration consumes energy and reduces photosynthetic efficiency, so it does not promote growth. The likely mistake is choosing both because both processes occur in photosynthetic tissues, although their effects are opposite.

1463. The glycolate produced diffuses into the membrane bounded organelles called____________?

• A. Glyoxisomes
• B. Peroxisomes
• C. Lysosomes
• D. Mitochondria

Explanation: Glycolate formed during photorespiration diffuses into peroxisomes, where it is oxidized and converted into compounds that continue the photorespiratory pathway. Students may choose glyoxisomes because the name resembles peroxisomes, but glyoxisomes are specialized mainly for handling fats in germinating seeds.

1464. ___________ respiration is the process by which cell utilized oxygen and produces CO2 ?

• A. Cellular
• B. Organismic
• C. Both of these
• D. None of these

Explanation: Cellular respiration is the series of reactions in cells that uses oxygen in aerobic conditions and releases carbon dioxide while transferring energy into ATP. Students may choose organismic respiration because it describes breathing and gas exchange by the whole organism, not the intracellular energy-releasing pathway.

1465. ___________ respiration is directly involved in the production of energy, necessary for all living activities?

• A. Organismic
• B. Cellular
• C. Both of these
• D. None of these

Explanation: Cellular respiration directly produces ATP by oxidizing glucose and other respiratory substrates, and ATP supplies usable energy for cellular activities. Students may choose organismic respiration because breathing supplies oxygen, but breathing itself does not directly generate most cellular ATP.

1466. Breaking of terminal phosphate of ATP releases about ___________ Kcal of energy?

• A. 6.1
• B. 6.3
• C. 7.1
• D. 7.3

Explanation: Hydrolysis of ATP's terminal phosphate releases about 7.3 kcal per mole of ATP under standard biochemical conditions. Students may choose 6.1 kcal per mole because energy values vary with conditions, but 7.3 kcal per mole is the standard textbook value used for ATP hydrolysis.

1467. ATP are consumed during___________?

• A. Glycolysis
• B. Kreb's cycle
• C. Light dependent phase
• D. none of these

Explanation: ATP is consumed during the investment phase of glycolysis, where 2 ATP per glucose are used to phosphorylate intermediates before ATP is produced later. Students may choose the Krebs cycle because it is part of respiration, but the cycle produces ATP or GTP rather than consuming ATP in the usual pathway.

1468. From one pyruvate passing through Kreb's cycle, how many NADH are formed?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: One pyruvate produces one NADH during its conversion to acetyl-CoA and two more NADH during its two turns of the Krebs cycle, giving 1 + 2 = 3 NADH per pyruvate. Students may choose 2 because they count only the NADH made directly in the Krebs cycle and omit the link reaction.

1469. In Anaerobic respiration only __________ % of the energy present within the chemical bond of glucose is converted into ATP?

• A. 1%
• B. 2%
• C. 3%
• D. 4%

Explanation: Anaerobic respiration captures only about 2% of glucose's stored chemical energy in ATP because glycolysis is the only energy-yielding stage and produces a net 2 ATP per glucose. Students may choose 4% because they double the percentage by counting the two ATP-producing steps without considering the much greater total energy stored in glucose.

1470. Final acceptor of electrons in respiratory chain is____________?

• A. NADH
• B. Cytochrome a3
• C. Water
• D. Oxygen

Explanation: Oxygen is the final electron acceptor in the respiratory chain; it combines with electrons and hydrogen ions to form water at the end of oxidative phosphorylation. Students may choose cytochrome a3 because it transfers electrons immediately before oxygen, but it is an electron carrier rather than the final acceptor.