All Free Biology MCQs with Answers

• A. Iron
• B. Sodium
• C. Potassium
• D. Magnesium

Explanation: The porphyrin ring of chlorophyll contains a magnesium atom at its center.

• A. Tracheids
• B. Trachea
• C. Collenchyma
• D. Sieve tubes

Explanation: Phloem tissues are composed of sieve tubes, which are specialized cells responsible for transporting organic materials, such as sugars…

• A. Nitrogen
• B. Oxygen
• C. Carbon monoxide
• D. Carbon dioxide

Explanation: Chloroplasts are the site of photosynthesis in plant cells, where carbon dioxide (CO2) is fixed into organic molecules.

• A. Thylakoid
• B. Grana
• C. Stroma
• D. Christa

Explanation: Plant cells synthesize sugar in the stroma of chloroplasts. The stroma contains the enzymes necessary for the Calvin cycle, which is the…

• A. plant hormones
• B. carotenoids
• C. plant enzymes
• D. water present in mysophyll tissue

Explanation: Carotenoids are the photoprotective pigments that absorb light of high intensity and transfer the energy to chlorophyll for…

• A. nitrogen
• B. magnesium
• C. potassium
• D. both a and b

Explanation: Chlorosis is the yellowing of leaves due to a lack of chlorophyll, often caused by nutrient deficiencies.

• A. phosphorus
• B. potassium
• C. magnesium
• D. nitrogen

Explanation: The correct answer is phosphorus. Phosphorus is essential for the development of roots, flowers, seeds, and fruit.

• A. hormones secreting glands
• B. water secreting glands
• C. nectar secreting glands
• D. enzymes secreting glands

Explanation: Hydathodes are holes in leaf magrin through which water is secreted out during guttation.

• A. hydroxyl group
• B. methyl group
• C. carboxyl group
• D. aldehyde group

Explanation: Chlorophyll 'a' is an essential pigment in photosynthesis, and its structure includes a porphyrin ring.

• A. Hydrophytes
• B. Xerophytes
• C. Mesophytes
• D. All of the above

Explanation: Sunken stomata are a characteristic adaptation found in xerophytes, which are plants adapted to dry, arid environments.

• A. Violet blue light
• B. Orange light
• C. Blue-red light
• D. Red, orange light

Explanation: Chlorophyll a and b primarily absorb blue and red light. Blue light, being high in energy, excites electrons to a higher energy level…

• A. Vessels, tracheids, parenchyma
• B. Sieve tubes, companion cells, fibers
• C. Parenchyma, sieve tube, vessels
• D. Fibers, companion cells, tracheids

Explanation: Xylem tissue is primarily responsible for water transport in plants and consists of four main components: tracheids, vessels, parenchyma…

• A. Carotenes
• B. Xanthophylls
• C. Chlorophyll - C
• D. Both (A) and (B)

Explanation: The carotenoids are divided into two main classes: carotenes and xanthophylls.

• A. Adhesion
• B. Cohesion
• C. Collision
• D. Corrosion

Explanation: The correct answer is Adhesion. Adhesion describes the attraction between unlike molecules.

• A. Water potential
• B. Pressure potential
• C. Solute potential
• D. Osmotic potential

Explanation: The correct answer is Solute potential. The concentration of water molecules is inversely proportional to solute potential because when…

• A. Grasses
• B. Under ground stems
• C. Fruit-nuts
• D. Cabbage leaves

Explanation: Bulliform cells or motor cells are large, bubble-shaped epidermal cells that occur in grps on the upper surface of the leaves of many…

• A. N2
• B. O2
• C. CO2
• D. NH3

Explanation: The stroma of chloroplasts is where the Calvin cycle occurs, which is responsible for fixing carbon dioxide (CO2) into organic molecules…

• A. Methyl group
• B. Carboxyl group
• C. Aldehyde group
• D. Hydroxyl group

Explanation: The porphyrin ring in chlorophyll-b is specifically attached to an aldehyde group, which includes a carbonyl group (C=O) bonded to a…

• A. Magnesium
• B. Iron
• C. Phosphorus
• D. Potassium

Explanation: The correct answer is Magnesium. Magnesium is a critical component of chlorophyll, and its deficiency leads to chlorosis-a condition where…

• A. Halophytes
• B. Mesophytes
• C. Sciophytes
• D. Xerophytes

Explanation: Sciophytes are plants that grow in moderate to low intensity of light under the cover of large trees.