Pre AP Biology -CELLS 6.1 Photosynthesis- MCQ Exam Style Questions -New Syllabus

Pre AP Biology -CELLS 6.1 Photosynthesis- MCQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Biology -CELLS 6.1 Photosynthesis- 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 processes contributes to the movement of water up a plant stem?

a. active transport of water into the root hairs

b. absorption of raindrops on a leaf’s epidermis

c. higher (less negative) water potential in the leaf’s mesophyll layer than in the xylem

d. cohesion of water molecules in the stem and leaf xylem

▶️ Answer/Explanation

Detailed solution

The correct option is d.
Water moves upward through the xylem primarily due to the Cohesion-Tension Theory.
Cohesion allows water molecules to stick to one another via hydrogen bonding, forming a continuous column.
Transpiration in the leaves creates a negative pressure (tension) that pulls this column upward.
Water potential actually decreases (becomes more negative) as you move from the roots to the leaves.
Water enters root hairs via osmosis (passive transport), not active transport.
Therefore, the structural integrity of the water column depends on the cohesion of water molecules.

Question

Which of these situations is characteristic of cell division in bacteria?

a. Several chromatids are separated at anaphase.
b. Binary fission produces four daughter cells.
c. Replication begins at the $ori$, and the two new DNA molecules separate.
d. The daughter cells receive different genetic information from the parent cell.

▶️ Answer/Explanation

Detailed solution

The correct answer is c.
Bacteria undergo a process called binary fission for cell division.
DNA replication initiates at a specific site on the circular chromosome called the $ori$ (origin of replication).
As the DNA replicates, the two $ori$ regions move toward opposite ends of the cell.
The cell elongates, and the two new DNA molecules are actively separated.
A septum forms in the center, dividing the parent cell into two identical daughter cells.
Options a and b are incorrect because bacteria lack a mitotic spindle/anaphase and produce two cells, not four.
Option d is incorrect because binary fission is an asexual process resulting in genetically identical clones.

Question

The Calvin cycle is sometimes referred to as “dark reactions.” Which of these statements tells us why this is misleading?

a. RuBisCo is rapidly degraded in the dark.
b. $\text{NAD}^+$ generated by the light reactions is needed to activate 3-phosphoglycerate.
c. In the dark, oxygen builds up in the chloroplast and inhibits RuBisCo activity, which prevents the Calvin cycle from occurring.
d. The Calvin cycle in $\text{C}_3$ plants usually occurs at the same time that $\text{NADPH}$ and $\text{ATP}$ are created.

▶️ Answer/Explanation

Detailed solution

The correct option is d.
The term “dark reactions” is misleading because the Calvin cycle does not actually require darkness to proceed.
In fact, the cycle relies on $\text{ATP}$ and $\text{NADPH}$ produced during the light-dependent reactions.
These energy carriers are short-lived and are generated continuously while light is available.
Therefore, the Calvin cycle typically occurs simultaneously with the light reactions during the day.
Additionally, several key enzymes in the cycle are light-activated to ensure efficiency.
Option b is incorrect because the light reactions generate $\text{NADPH}$, not $\text{NAD}^+$.

Pre AP Biology -CELLS 6.1 Photosynthesis- MCQ Exam Style Questions -New Syllabus