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Pre AP Biology -CELLS 3.3 Cell Size and Diffusion- MCQ Exam Style Questions -New Syllabus 2025-2026

Pre AP Biology -CELLS 3.3 Cell Size and Diffusion- MCQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Biology -CELLS 3.3 Cell Size and Diffusion- MCQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.

Pre AP Biology – MCQ Exam Style Questions- All Topics

Question

Which of these statements describes why a seed coat ruptures?
a. The cotyledons have emerged.
b. Enzymes have been activated in the endosperm.
c. Water has entered the seed by imbibition.
d. Cell division has suddenly increased in the cotyledons.
▶️ Answer/Explanation
Detailed solution

The correct option is c.
Germination begins when a dry seed takes up water through a process called imbibition.
As water enters, the internal tissues of the seed swell significantly due to hydration.
This swelling creates massive internal turgor pressure against the rigid seed coat (testa).
The physical pressure eventually exceeds the tensile strength of the coat, causing it to rupture.
This rupture allows the embryo to expand and the radicle to emerge into the soil.
Other factors like enzyme activation and cell division occur after or alongside hydration, but the physical break is caused by water intake.

Question

Which of the following will happen if you place a plant cell with $\psi_s$ of $-0.4\text{ MPa}$ and $\psi_p$ of $0.2\text{ MPa}$ into a chamber filled with pure water that is pressurized at $0.5\text{ MPa}$?
a. Water will flow into the cell.
b. Water will flow out of the cell.
c. The cell will be crushed.
d. The cell will explode.
▶️ Answer/Explanation
Detailed solution

The water potential of the plant cell is calculated as $\psi_{cell} = \psi_s + \psi_p = -0.4\text{ MPa} + 0.2\text{ MPa} = -0.2\text{ MPa}$.
The water potential of the chamber is calculated as $\psi_{chamber} = \psi_s + \psi_p = 0\text{ MPa} + 0.5\text{ MPa} = 0.5\text{ MPa}$.
Water always moves from a region of higher water potential to a region of lower water potential.
Since $0.5\text{ MPa} > -0.2\text{ MPa}$, the water potential of the chamber is higher than that of the cell.
Therefore, water will flow from the chamber into the cell.
The correct option is a.

Question

Which type of transport do roots utilize to take up ions from the soil? Why?
a. active transport, because the needed ions concentrate much more in the root than in the soil
b. passive transport, because the needed ions concentrate much more in the root than in the soil
c. active transport, because the needed ions concentrate much more in the soil than in the roots
d. passive transport, because the needed ions concentrate much more in the soil than in the roots
▶️ Answer/Explanation
Detailed solution

The correct option is a.

Plants often require a higher concentration of mineral ions inside their root cells than what is available in the surrounding soil.
To move these ions against a concentration gradient, the plant must use active transport.
This process requires energy in the form of $ATP$ to power specific membrane pump proteins.
Because the internal ion concentration is higher than the soil, passive transport (diffusion) would actually move ions out of the root.
Therefore, root hair cells utilize active transport to effectively “pull” nutrients inward.
This ensures the plant maintains the necessary electrochemical gradients for growth and water uptake.

Question

Which of the following is a specific advantage of a dendritic growth pattern?
a. Roots and shoots can continuously grow into new spaces.
b. The plant will be more stable (e.g., less likely to tip over).
c. The plant can survive loss of part of a root or shoot system.
d. It provides a large surface area for uptake of nutrients and light.
▶️ Answer/Explanation
Detailed solution

The correct option is d.
A dendritic (tree-like) branching pattern maximizes the surface area-to-volume ratio.
In the shoot system, branching spreads leaves out to capture maximum solar energy for photosynthesis.
In the root system, extensive branching increases the contact points with soil for water and nutrient absorption.
While other options describe general plant traits, increased surface area is the primary geometric advantage of this specific pattern.
This allows the plant to efficiently interact with its heterogeneous environment.

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