HESI A2 Biology Practice Test

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: B

Rationale: The correct answer is B because animal cells do not use chloroplasts to gain energy, they use mitochondria for cellular respiration. Lysosomes in animal cells break down old cells (A) and plant cells have a cell wall (C). Choice D is incorrect as B is false.

Correct Answer: A

Rationale: Epithelial cells are correct to be classified as polarized because they have distinct apical and basal surfaces. The apical surface faces the external environment or a body cavity, while the basal surface is anchored to the underlying connective tissue. This polarity is essential for the specialized functions of epithelial cells, such as absorption, secretion, and transportation. Therefore, choice A is the correct answer. Choices B and C are incorrect because epithelial cells are not neutral and are not necessarily larger than other cells. Choice D is incorrect because epithelial cells do have unique characteristics that differentiate them from other cell types.

Correct Answer: B

Rationale: The correct answer is B: Troposphere, stratosphere, mesosphere, thermosphere, exosphere. Rationale: 1. Troposphere: Closest to the Earth's surface where weather occurs. 2. Stratosphere: Contains the ozone layer, which absorbs UV radiation. 3. Mesosphere: Middle layer where meteors burn up. 4. Thermosphere: Upper layer with high temperatures and auroras. 5. Exosphere: Outermost layer where atmosphere transitions to space. Summary: A: Incorrect order, starts with exosphere which is the outermost layer. C: Incorrect order, mesosphere is placed before troposphere. D: Incorrect order, thermosphere comes before troposphere.

Correct Answer: D

Rationale: The correct answer is D: species. Within the biological hierarchical system, species is the least inclusive category. A species consists of organisms that can interbreed and produce fertile offspring. Moving up the hierarchy, species are grouped into genera, then families, orders, classes, phyla, and finally kingdoms. Phylum (A), order (B), and kingdom (C) are all more inclusive categories than species. Phylum includes multiple classes, order includes multiple families, and kingdom includes multiple phyla. Therefore, species is the least inclusive category within this system.