HESI A2 Practice Test Biology

Correct Answer: C

Rationale: The correct answer is C: Selectively permeable. The phospholipid bilayer of the cell membrane allows the passage of certain molecules while restricting others based on their size, charge, and solubility. This selective permeability enables the cell to regulate the movement of substances in and out, maintaining homeostasis. Option A is incorrect because the cell membrane is not impermeable; it allows some substances to pass through. Option B is incorrect as it suggests all molecules can freely pass through, which is not the case. Option D is incorrect as it contradicts itself by combining selective and impermeable, which is not a characteristic of the cell membrane.

Correct Answer: C

Rationale: The correct answer is C: Synthesize proteins. Ribosomes are responsible for protein synthesis in the cell by translating mRNA into specific amino acid sequences. They are composed of rRNA and protein subunits. Ribosomes do not break down cellular waste (A), organize cellular division (B), or provide cellular structure (D). Cellular waste breakdown is typically performed by lysosomes, cellular division is organized by the centrosome, and cellular structure is maintained by the cytoskeleton.

Correct Answer: A

Rationale: The correct answer is A because DNA contains the genetic information needed for the synthesis of enzymes, which are crucial for metabolic activities in the cell. Enzymes are proteins that catalyze chemical reactions within the cell, allowing essential metabolic processes to occur. DNA serves as a template for the production of specific enzymes through the process of transcription and translation. Choices B, C, and D are incorrect because DNA does not directly play a role in stabilizing the cell wall, initiating cell division, or preventing diffusion of nutrients. These processes are regulated by other cellular components and mechanisms.

Correct Answer: B

Rationale: The correct answer is B: ATP. ATP (adenosine triphosphate) is the primary molecule responsible for storing and transferring energy in cells through its high-energy phosphate bonds. Glucose (choice A) is a source of energy but not a storage molecule. Fatty acids (choice C) are primarily used for long-term energy storage. Starch (choice D) is a polysaccharide used for energy storage in plants, but ATP is the main energy currency in all cells for immediate use.

Correct Answer: D

Rationale: During meiosis I, the chromosome number is reduced from diploid to haploid. This occurs during the process of homologous chromosomes separating, resulting in two daughter cells with half the number of chromosomes. In contrast, in S phase, DNA replication occurs, while interphase is a period of cell growth and preparation for cell division. Mitosis is a process where a diploid cell divides into two identical diploid daughter cells, maintaining the same chromosome number. Thus, meiosis I is the only phase where the chromosome number is reduced from diploid to haploid, making it the correct answer.