All Free Biology MCQs with Answers

1261. ___________ potential is the measure of the change in water potential of a system due to the presence of solute molecules?

• A. Osmotic
• B. Pressure
• C. Both of these
• D. None of these

Explanation: Osmotic or solute potential measures the change in water potential caused by dissolved solute particles, which lower the water potential of a solution. Students may choose b because pressure potential is also part of water potential, but it results from physical pressure rather than solute concentration.

1262. The movement of water molecules from a region of higher water potential to a region of lower water potential (through membrane)

• A. Deffusion
• B. Osmosis
• C. Active transport
• D. None of these

Explanation: Osmosis is the net movement of water through a selectively permeable membrane from higher water potential to lower water potential. Diffusion is a broader term for particle movement and does not specifically require water crossing a membrane, so students may choose a.

1263. The pressure generated when water enters & inflates plant cells is called ___________ potential?

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

Explanation: When water enters a plant cell, it pushes the plasma membrane against the cell wall and produces turgor pressure, represented as pressure potential. Students may choose b because entry of water is caused by osmotic effects, but the pressure generated inside the inflated cell is pressure potential.

1264. In plants, water potential is determined by major factors?

• A. Three
• B. Four
• C. Two
• D. Five

Explanation: The two major components used for plant water potential are solute potential and pressure potential, expressed as Ψw = Ψs + Ψp. Students may choose a if they count water potential itself as a separate factor, but it is the overall value being determined, not an additional component in this simplified model.

1265. In the root cells _______ pathway becomes discontinuous in the endodermis due to the presence of casparian strip.

• A. Tonoplast
• B. Apoplast
• C. Symplast
• D. Vacuolar.

Explanation: The apoplast is the continuous pathway through cell walls and intercellular spaces, but the Casparian strip blocks it at the endodermis. Water and ions must then cross a cell membrane and enter the symplast, so students may choose c by identifying the pathway used after the blockage rather than the one made discontinuous.

1266. The diffusion of ions along with water also takes place by mass flow system along the ________ path?

• A. Tonoplast
• B. Apoplast
• C. Symplast
• D. Vacuolar

Explanation: Mass flow through cell walls and intercellular spaces occurs along the apoplast pathway, which does not require water to cross plasma membranes at every cell. Students may choose c because ions eventually enter the symplast for selective control, but that is not the pathway of the initial wall-based mass flow.

1267. The site/s where most of the uptake of water and minerals take place is/are__________?

• A. Root hairs
• B. Root cells
• C. Underground stem
• D. All of these

Explanation: Root hairs greatly increase the surface area in contact with the soil and have thin walls, making them the main sites for water and mineral absorption. Students may choose b because absorption occurs in root cells generally, but root hairs are the specialised cells responsible for most uptake.

1268. There are __________ types of nutrients needed by plants besides light to carry out photosynthesis

• A. Two
• B. Three
• C. Four
• D. Five

Explanation: In the usual school-level description, photosynthesis requires three materials besides light: water, carbon dioxide and chlorophyll, which absorbs light energy. Students may choose a by counting only the raw materials water and carbon dioxide, but this omits chlorophyll's essential role in capturing light.

1269. Higher turgor pressure in a plant cell is maintained by________________?

• A. Large number of vacoules in a plant cell.
• B. Higher ionic concentration inside vacuoles resulting from active pumping of ions at their tonoplastic membrane
• C. Higher osmotic pressure of the cell vacuole
• D. both b and c

Explanation: Active pumping of ions into the vacuole increases its solute concentration and therefore its osmotic pressure, drawing in water and raising turgor pressure. Both the higher ionic concentration and the resulting higher osmotic pressure are involved, so option d is correct; choosing only c misses the ion-pumping mechanism.

1270. Scurvy and beri - beri and caused by the deficiency of___________?

• A. Vitamin B and C
• B. Vitamin B and D
• C. Vitamin C and B
• D. Vitamin A and B

Explanation: Scurvy results from vitamin C deficiency, while beri-beri results from vitamin B1, or thiamine, deficiency. Therefore the pair is vitamin C and vitamin B. Students may choose a because it contains both vitamins but reverses the diseases and their deficiencies.