All Free Biology MCQs with Answers

3361. For every 3 molecules of carbon dioxide in the Calvin cycle, how much G3P is produced?

• A. 6
• B. 2
• C. 4
• D. 8

Explanation: The products in one turn of the Calvin cycle are 2 glyceraldehyde-3-phosphate (G3P) molecules, 3 ADP, and 2 NADP+.Therefore for every 3 molecules of CO2 in the Calvin cycle, 6G3P is produced.Hence, A is the correct option.

3362. Bacteriochlorophylls does not include which of the following?

• A. Chlorophyll e
• B. Chlorophyll b
• C. Chlorophyll c
• D. All of these options

Explanation: Bacteria use bacteriochlorophylls in photosynthesis without the production of energy. Bacteria only use bacteriochlorophylls for capturing light. Bacteriochlorophylls don't include chlorophylls e, b, or c.

3363. Which of the following light is least absorbed by plants?

• A. Orange blue
• B. Red
• C. Blue
• D. Green

Explanation: Green light is not as efficiently absorbed by chlorophyll, the pigment responsible for photosynthesis in plants, as compared to red and blue light. Chlorophyll primarily absorbs light in the blue and red regions of the electromagnetic spectrum. However, some green light is still absorbed and utilized by plants for photosynthesis, even though it is not as effective as blue and red light absorption.

3364. The part of chlorophyll molecule embedded in the core of thylakoid membrane is?

• A. Hydrophilic
• B. Hydrophobic
• C. Both of these
• D. None of these

Explanation: The part of the chlorophyll molecule that is embedded in the core of the thylakoid membrane is the hydrophobic tail. Chlorophyll is a pigment essential for photosynthesis, and it consists of a hydrophilic head and a hydrophobic tail. The hydrophilic head interacts with the aqueous environment of the thylakoid membrane, while the hydrophobic tail is embedded within the lipid bilayer of the thylakoid membrane itself. This arrangement allows chlorophyll to capture light energy and participate in the light reactions of photosynthesis, which take place in the thylakoid membrane.

3365. Which one is not an energy releasing process?

• A. Glycolysis
• B. Photosynthesis
• C. Respiration
• D. Krebs Cycle

Explanation: The correct answer is Photosynthesis. Photosynthesis is an endothermic process, meaning it requires energy input from sunlight to convert carbon dioxide and water into glucose and oxygen. In contrast, Glycolysis, Respiration, and the Krebs Cycle are all exothermic processes that release energy stored in glucose molecules to produce ATP, which is used by cells for various functions.

3366. Magnesium is important for the synthesis of which of the following?

• A. Chlorophyll
• B. Protein synthesis
• C. Glucose metabolism
• D. All of these

Explanation: Magnesium is essential for the synthesis of chlorophyll, the pigment responsible for capturing light energy in photosynthesis. It forms the central atom in the chlorophyll molecule, which is crucial for plants to convert sunlight into chemical energy. Magnesium is not directly involved in protein synthesis, which primarily requires nitrogen, or in the synthesis of glucose, although it does play a supportive role in glucose metabolism.

3367. Out of the 6 molecules of G3P, how many molecules are used to make glucose?

• A. 1
• B. 2
• C. 3
• D. 6

Explanation: The Calvin Cycle, the light-independent reactions of photosynthesis, produces three molecules of glyceraldehyde-3-phosphate (G3P) for every three molecules of carbon dioxide that enter the cycle. However, it takes two turns of the Calvin Cycle to produce one molecule of glucose. Each turn produces one molecule of G3P, and three G3P molecules are needed to form one molecule of glucose. Therefore, out of the 6 molecules of G3P produced in two turns of the Calvin Cycle, only 1 molecule is used to make glucose, and the remaining 5 molecules are used to regenerate the molecules needed to continue the cycle.

3368. What is the copper-containing protein involved in the ETC in plants?

• A. Pq
• B. Pc
• C. Pt
• D. Po

Explanation: Plastocyanin (Pc) is a copper-containing protein that plays a crucial role in the electron transport chain (ETC) during photosynthesis in plants and algae. Plastocyanin shuttles electrons between photosystem II (PSII) and photosystem I (PSI) within the thylakoid membrane of chloroplasts. The movement of electrons through the ETC in photosynthesis involves a series of protein complexes and cofactors. Plastocyanin serves as an electron carrier, transferring electrons from the cytochrome b6f complex (which is part of the ETC) to photosystem I.

3369. The Calvin cycle is:

• A. Inhibited by light
• B. Dependent upon light
• C. Independent of light
• D. Supported by light

Explanation: The Calvin cycle, also known as the dark reactions or light-independent reactions of photosynthesis, does not directly depend on light. Unlike the light-dependent reactions that occur in the thylakoid membranes and require light energy, the Calvin cycle takes place in the stroma of chloroplasts and can proceed in the absence of light. The Calvin cycle is a series of biochemical reactions that lead to the synthesis of carbohydrates (such as glucose) from carbon dioxide. It involves the fixation of carbon dioxide, the reduction of 3-phosphoglycerate to form glyceraldehyde-3-phosphate, and the regeneration of the initial carbon dioxide acceptor, ribulose-1,5-bisphosphate. The energy and reducing power needed for these reactions come from ATP and NADPH, which are produced during the light-dependent reactions.

3370. Which type of light causes the highest rate of photosynthesis?

• A. Blue
• B. Red
• C. Orange
• D. Violet

Explanation: Red causes the highest rate of photosythesis as it powers the synthesis of ATP and NADPH.