HESI A2 Biology Practice Test

Correct Answer: D

Rationale: The plasma membrane is a phospholipid bilayer, meaning it consists of two layers of phospholipid molecules. This arrangement forms a barrier that separates the cell from its external environment. The hydrophobic tails of the phospholipids face inward, while the hydrophilic heads face outward. This structure allows the membrane to control the movement of substances in and out of the cell. Choices A and B are incorrect as the membrane is not solely made of proteins. Choice C is incorrect as the membrane consists of a double layer of phospholipids, not a single layer.

Correct Answer: B

Rationale: The correct answer is B: smooth ER. The smooth ER is responsible for detoxifying multiple molecules through processes like drug metabolism and lipid synthesis. It contains enzymes that help break down toxins. The rough ER is primarily involved in protein synthesis, so it is not directly related to detoxification. Lysosomes are involved in breaking down cellular waste and are not specialized for detoxification. The Golgi apparatus is responsible for packaging and modifying proteins for transport, not detoxifying molecules. Therefore, the smooth ER is the most suitable organelle for detoxifying multiple molecules in a cell.

Correct Answer: C

Rationale: The correct answer is C: metabolism. Metabolism refers to the sum of all chemical reactions that occur in an organism to maintain life. It includes processes such as breaking down food, producing energy, and building new molecules. Respiration (B) is a specific type of metabolic process involving the release of energy. Product (A) refers to the end result of a chemical reaction, not the entire process. Synthesis (D) is a part of metabolism where new molecules are built, but it does not encompass all the chemical reactions in an organism.

Correct Answer: A

Rationale: The correct answer is A: A segment of DNA. Genes are segments of DNA that contain the instructions for building proteins and controlling various processes in an organism. DNA is the genetic material that carries hereditary information and is passed down from parents to offspring. Option B is incorrect because genes are not bead-like structures on chromosomes but are located within chromosomes. Option C is incorrect because genes are not protein molecules themselves but may code for proteins. Option D is incorrect because genes are not made up of RNA but rather DNA.

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.