HESI A2 Biology Practice Test

Correct Answer: A

Rationale: The correct answer is A: Adenine. Adenine is a nucleotide base that consists of two fused carbon rings, making it a purine base. The two rings in adenine are essential for its structure, function, and hydrogen bonding with thymine in DNA. The other choices, B, C, and D, are all pyrimidine bases, which have only one carbon ring. Therefore, adenine is the only base among the options that has two carbon rings, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Biomes. Biomes are large geographical areas characterized by specific climate, vegetation, and animal life. Tundra, savannas, grasslands, deserts, and rainforests are all examples of biomes. They are classified based on factors like temperature, precipitation, and flora/fauna. Biomasses (A) refer to the total mass of living organisms in a given area. Biospheres (B) are the regions of the Earth where life exists. Biodiversity (C) refers to the variety and variability of life forms in a specific habitat, not the specific types of habitats themselves.

Correct Answer: D

Rationale: Failed to generate a rationale after 5 retries.

Correct Answer: B

Rationale: The correct answer is B: Carrier proteins. Carrier proteins change shape to facilitate the movement of specific molecules across the membrane. They bind to the target molecule on one side of the membrane, undergo a conformational change, and release the molecule on the other side. This process is selective and energy-dependent. Option A (Diffusion) is incorrect because diffusion is a passive process that does not involve proteins changing shape to transport molecules. Option C (Channel proteins) is incorrect because channel proteins provide a passageway for specific molecules to move across the membrane but do not change shape to transport molecules. Option D (None of the above) is incorrect because carrier proteins specifically fit the description provided in the question.

Correct Answer: C

Rationale: The correct answer is C because plant cells have a rigid cell wall that prevents them from forming a contractile ring during cell division. The cell wall provides structural support, making it challenging for plant cells to constrict and pinch apart like animal cells. This rigidity limits the flexibility needed for the contractile ring to form and function effectively. Plant cells primarily rely on other mechanisms such as cell plate formation for division. Choices A and B are incorrect as they do not address the specific structural difference between plant and animal cells. Choice D is incorrect as it does not provide any relevant information on the topic.