All Free Biology MCQs with Answers

1481. Of the following, which one light - gathering?

• A. Antenna complex
• B. Reaction centre
• C. Photosystem
• D. None of these

Explanation: The antenna complex contains pigment molecules that capture light over a broad range of wavelengths and transfer the excitation energy to the reaction centre. The likely alternative is the reaction centre, but it performs the primary photochemical conversion rather than gathering most of the incoming light.

1482. Thylakoids in chloroplasts are stacked into___________?

• A. Grana
• B. Stroma
• C. Nucleus
• D. None of these

Explanation: Thylakoids are flattened membrane sacs, and stacks of these sacs are called grana. The likely mistake is choosing stroma, which is the surrounding fluid region of the chloroplast and does not consist of stacked membranes.

1483. Reduction in photosynthesis is of____________?

• A. O2
• B. CO2
• C. H2O
• D. light energy

Explanation: In photosynthesis, carbon dioxide is reduced to carbohydrates because it gains hydrogen or electrons supplied through the light reactions. Students may choose oxygen because water is split and oxygen is released, but oxygen is a product of oxidation of water, not the substance being reduced.

1484. Which of the following pigment is Blue- green in colour?

• A. Chlorophyll a
• B. Chlorophyll b.
• C. Chlorophyll c
• D. Chlorophyll d.

Explanation: Chlorophyll a is blue-green because its absorption spectrum and molecular structure give it that characteristic colour. Chlorophyll b is commonly confused with it, but chlorophyll b is yellow-green and functions mainly as an accessory pigment.

1485. Stomata cover only ______________ of leaf surface?

• A. 0.03 - 0.04%
• B. 10%
• C. 1-2 %
• D. 50%

Explanation: Stomata occupy only a small fraction of the leaf surface, commonly estimated at about 1 to 2%, while still providing extensive openings for gas exchange. The likely distractor is 10%, which overestimates their area because stomata are numerous but individually very small.

1486. Molecular formula of chlorophyll 'a' molecule is___________?

• A. C55H72O5N4Mg
• B. C55H70O6N4Mg
• C. C50H72O6N4Mg
• D. C55H70O5N4Mg

Explanation: Chlorophyll a has the molecular formula C55H72O5N4Mg, containing a magnesium atom at the centre of its porphyrin-like ring. The likely alternative is chlorophyll b's formula, C55H70O6N4Mg, because it differs by a substituted side group, but that is not the formula of chlorophyll a.

1487. Photosynthesis carried out by terrestrial plants is _________ of total photosynthesis?

• A. 1-2%
• B. 5%
• C. 10%
• D. 20%

Explanation: Terrestrial plants contribute about 10% of the total global photosynthesis, while aquatic organisms in oceans, lakes, and ponds perform most of the remainder. Students may choose 20% by overestimating the contribution of forests and crops compared with the vast photosynthetic area of aquatic organisms.

1488. Which of the following statement about the head of a chlorophyll molecule is incorrect?

• A. It is a porphyrin ring or tetrapyrrole ring structure
• B. It is flat, square and light absorbing
• C. Composed of carbon and nitrogen atoms with Magnesium as central metal ion, which is coordinated with nitrogen.
• D. It is hydrophobic

Explanation: The chlorophyll head is a hydrophilic porphyrin ring containing carbon, nitrogen, and a central magnesium ion, whereas its phytol tail is hydrophobic. Students most likely choose another option by confusing the hydrophobic phytol tail with the light-absorbing head.

1489. Of the following, which one causes higher production of food in green plants?

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

Explanation: Red light is absorbed efficiently by chlorophyll and drives photosynthesis at a high rate, especially near the red absorption peak of chlorophyll a. Blue light is also highly effective, so students may choose blue if they remember the two major absorption regions but overlook that red is the expected single choice here.

1490. Chlorophyll is insoluble in_____________?

• A. Carbon tetrachloride
• B. Alcohol
• C. Organic solvents
• D. Water

Explanation: Chlorophyll is a lipid-soluble pigment, so it dissolves in alcohol and other organic solvents but is insoluble in water. Students may choose carbon tetrachloride because it is less familiar, although chlorophyll can dissolve in suitable nonpolar organic solvents.