HESI A2 Practice Test Biology

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: 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: B

Rationale: The correct answer is B: Ribosome. Ribosomes are responsible for organizing protein synthesis by translating mRNA into protein. They are the cellular machinery where protein synthesis occurs. The nucleus (A) houses the genetic material but does not directly participate in protein synthesis. Lysosomes (C) are responsible for cellular waste digestion, not protein synthesis. Vacuoles (D) are primarily storage organelles and do not play a direct role in organizing protein synthesis. In summary, the ribosome is the correct answer as it is the key organelle directly involved in protein synthesis within the cell.

Correct Answer: C

Rationale: The correct answer is C: ribosome. Ribosomes are the organelles responsible for organizing protein synthesis. They are the site where proteins are assembled based on instructions from the cell's DNA. Ribosomes can be found in the cytoplasm and on the endoplasmic reticulum. Mitochondria (A) are responsible for energy production, the nucleus (B) contains genetic material but does not directly organize protein synthesis, and vacuoles (D) are primarily involved in storage and maintaining cell structure. Therefore, the ribosome is the only organelle directly involved in protein synthesis among the choices provided.

Correct Answer: C

Rationale: The correct answer is C: covalent. In DNA, the bond connecting sugar and phosphate is a covalent bond. This is because covalent bonds involve the sharing of electrons between atoms, which is essential for forming the strong backbone structure of the DNA molecule. Hydrogen bonds (choice A) are important for holding the nitrogenous bases together in the DNA double helix, but they do not connect sugar and phosphate. Ionic bonds (choice B) involve the transfer of electrons between atoms, not sharing, and are not typically found in the structure of DNA. "Overt" (choice D) is not a type of chemical bond and is an incorrect term in this context. Thus, the correct choice is covalent based on the nature of the bond required to connect sugar and phosphate in DNA.