Pre AP Biology -CELLS 2.1 Cell Structure and Function- MCQ Exam Style Questions -New Syllabus
Pre AP Biology -CELLS 2.1 Cell Structure and Function- MCQ Exam Style Questions – New Syllabus 2025-2026
Pre AP Biology -CELLS 2.1 Cell Structure and Function- MCQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.
▶️ Answer/Explanation
The correct option is c. a mature ovule.
In seed plants, the ovule is the structure that contains the female gametophyte.
After fertilization occurs, the zygote develops into an embryo.
The integuments of the ovule thicken and harden to become the seed coat.
Therefore, a seed is biologically defined as a ripened or mature ovule.
By contrast, a mature ovary typically develops into the fruit.
The endosperm is merely a nutrient tissue found inside many seeds.
A megaspore is a haploid cell that precedes the formation of the ovule’s contents.
▶️ Answer/Explanation
Translocation begins with phloem loading, where sucrose is moved into the phloem.
Companion cells use ATP to actively pump \(H^+\) ions out, creating a gradient.
Sucrose is then moved into companion cells via cotransport with these \(H^+\) ions.
From companion cells, sucrose is pumped into sieve tube members against its concentration gradient.
This high solute concentration causes water to enter from the xylem, increasing turgor pressure.
The resulting pressure gradient drives the bulk flow of sap from source to sink.
▶️ Answer/Explanation
The correct answer is b.
In an open container, the pressure potential of the solution ($\Psi_{p,\text{sol}}$) is $0\text{ MPa}$.
Therefore, the water potential of the solution is $\Psi_{w,\text{sol}} = \Psi_{s,\text{sol}} = -0.3\text{ MPa}$.
Since the cell maintains a constant volume, it is in dynamic equilibrium with the solution.
This means the cell’s water potential ($\Psi_{w,\text{cell}}$) must also be $-0.3\text{ MPa}$.
Using the formula $\Psi_w = \Psi_s + \Psi_p$, we set $-0.3 = -0.65 + \Psi_{p,\text{cell}}$.
Solving for pressure potential gives $\Psi_{p,\text{cell}} = -0.3 – (-0.65) = +0.35\text{ MPa}$.