when plants do not receive enough water their photosynthetic rate drops this is because

HESI A2

HESI A2 Biology Practice Test

1. When plants do not receive enough water, their photosynthetic rate drops. This is because:

A. water is a raw material for the light reactions in photosynthesis
B. carbon dioxide is not available
C. water provides the carbon atoms used to make sugar
D. not enough oxygen is produced to keep fermentation running

Correct answer: A

Rationale: When plants do not receive enough water, their photosynthetic rate drops because water is a raw material required for the light reactions in photosynthesis. In the light reactions, water is split to provide electrons, which are then utilized to produce energy carriers used in converting carbon dioxide into glucose during the Calvin cycle. Therefore, without sufficient water, the light reactions cannot proceed effectively, ultimately leading to a decrease in photosynthetic rate. Choice B is incorrect because carbon dioxide is a separate raw material needed for the Calvin cycle, not the light reactions. Choice C is incorrect as water provides electrons, not carbon atoms, for photosynthesis. Choice D is incorrect because fermentation is not directly related to photosynthesis; oxygen is produced during photosynthesis, not fermentation.

2. What is the binding membrane of an animal cell called?

A. Biological membrane
B. Cell coat
C. Unit membrane
D. Plasma membrane

Correct answer: D

Rationale: The correct answer is D: Plasma membrane. The plasma membrane surrounds the cell and acts as an interface between the living interior of the cell and the nonliving exterior. It plays a vital role in maintaining the cell's integrity, regulating the passage of substances in and out of the cell, and facilitating communication with other cells. Choices A, B, and C are incorrect because the term 'plasma membrane' specifically refers to the binding membrane of an animal cell, distinguishing it from other types of membranes or coatings found in cells.

3. Which part of cellular respiration produces the greatest amount of ATP?

A. electron transport chain
B. glycolysis
C. citric acid cycle
D. fermentation

Correct answer: A

Rationale: The electron transport chain (ETC) produces the greatest amount of ATP during cellular respiration. This process occurs in the inner mitochondrial membrane and involves the transfer of electrons through a series of protein complexes, creating a proton gradient that drives the synthesis of ATP. By utilizing the energy from the electron carriers NADH and FADH2 produced in earlier stages of cellular respiration, the ETC can generate a large amount of ATP efficiently through oxidative phosphorylation. Glycolysis only produces a small amount of ATP in comparison to the ETC. The citric acid cycle generates some ATP but not as much as the ETC. Fermentation does not produce ATP through oxidative phosphorylation and yields a much smaller amount of ATP compared to the ETC.

4. Which one of the following best describes the function of a cell membrane?

A. It controls the substances entering and leaving the cell.
B. It maintains the cell's shape.
C. It controls the substances entering the cell.
D. It supports the cell's structures.

Correct answer: A

Rationale: The correct answer is A. The function of a cell membrane is to control the substances entering and leaving the cell. The cell membrane is selectively permeable, allowing it to regulate the movement of ions and molecules in and out of the cell to maintain internal balance and proper function. Choice B is incorrect because while the cell membrane does provide some structural support, its primary function is not to maintain the cell's shape. Choice C is incorrect because the cell membrane controls both the substances entering and leaving the cell, not just those entering. Choice D is incorrect as the primary function of the cell membrane is not to support the cell's structures but to regulate the movement of substances.

5. Select the strand of DNA that would match this segment: ACTTGCA

A. TGAACGT
B. GACCATG
C. ACTTGCA
D. None of the above

Correct answer: A

Rationale: The correct match for the DNA segment ACTTGCA is TGAACGT. In DNA, adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). Therefore, the complementary strand to ACTTGCA should be TGAACGT, making choice A the correct answer. Choice B (GACCATG) does not follow the base pairing rules; hence, it is incorrect. Choice C (ACTTGCA) is the original segment, not its complementary strand. Choice D is incorrect as well because a matching strand does exist.