All Free Biology MCQs with Answers

4071. During the first step of reduction phase of Calvin cycle, following change occurs:

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: In first stage of reduction phase assimilatory power is utilized and 3PGA is converted into 1,3 BPGA.

4072. The assimilatory and reducing powers synthesized in light reaction of photosynthesis are utilized in:

• A. Fixation phase of Calvin cycle
• B. Regeneration phase of Calvin cycle
• C. Reduction phase of Calvin cycle
• D. Condensation phase of Calvin cycle

Explanation: The Calvin cycle consists of several phases, including the fixation, reduction, and regeneration phases. The reduction phase is where the assimilatory and reducing powers (ATP and NADPH) are utilized. In this phase, carbon dioxide (CO2) is converted into carbohydrate molecules (such as glucose) using the ATP and NADPH produced in the light reactions. This process involves the reduction of carbon dioxide and the incorporation of the energy and electrons from ATP and NADPH into the newly synthesized carbohydrate molecules.

4073. The phase of Calvin cycle in which less ATPs of light reaction are used is:

• A. Fixation
• B. Regeneration
• C. Reduction
• D. Reduction and Regeneration

Explanation: Only 3ATPs are used to regenerate 3RuBP from 5 G.3.P.

4074. The number of CO2, NADPH2 and ATP molecules required to synthesize one maltose molecule from the output of Calvin cycle is respectively:

• A. 3, 6, 9
• B. 6, 12, 18
• C. 12, 24, 36
• D. 24, 48, 72

Explanation: As synthesis of glucose requires 6, 12, 18 molecules of CO2, NADPH and ATPs respectively, maltose consists of two glucose molecules.

4075. The ratio of CO2, NADPH2 and ATP molecules required to synthesize starch from the output of Calvin cycle is:

• A. 1, 2, 3
• B. 3, 6, 9
• C. 6, 12, 18
• D. 12, 24, 36

Explanation: Ratio of input of Calvin Cycle will remain same.

4076. C6H12O6 ⎯→ 2C3H4O3 + Energy. The given equation represents the:

• A. Oxidation of pyruvate
• B. Glycolysis
• C. Kreb's cycle
• D. TCA cycle

Explanation: It indicates formation of two molecules of pyruvate from one molecule of glucose.

4077. Biologists believe that in the first cell that was organized on earth, a reaction may have occurred which was identical to:

• A. Oxidation of pyruvate
• B. Glycolysis
• C. Kreb's cycle
• D. TCA cycle

Explanation: Glycolysis is such a process which is found in both prokaryotes and eukaryotes. It occurs in cytoplasm. Without glycolysis there is no other option for provision of energy to the cell.

4078. Cellular respiration depending upon the type of the cell and prevailing conditions varies from the step after:

• A. Oxidation of pyruvate
• B. Citric acid cycle
• C. Glycolysis
• D. Oxidative phosphorylation

Explanation: If aerobic conditions prevail after glycolysis it will follow the path of oxidation of pyruvate and Kreb's cycle otherwise it will follow the path of lactic acid fermentation or alcoholic fermentation.

4079. Alcoholic fermentation, lactic acid fermentation and aerobic respiration are the three ways for the processing of:

• A. Pyruvate in the cell
• B. Glucose in the cell
• C. Acetate in the cell
• D. Organic food in cell

Explanation: After glycolysis cell gets two molecules of pyruvate. After formation of pyruvate there comes oxidation of pyruvate and Krebs cycle, if oxygen is present and fermentation (Alcoholic or lactic acid fermentation) occurs, if oxygen is absent.

4080. Pick up the one which is anaerobic:

• A. Fermentation
• B. Oxidative phosphorylation
• C. Respiratory chain
• D. Krebs cycle

Explanation: Fermentation is an anaerobic process which is also called as anaerobic respiration.