HESI A2 Biology Practice Test 2024

Correct Answer: B

Rationale: The correct answer is B: Nucleotides. DNA is made up of nucleotides, which are composed of a sugar molecule, a phosphate group, and a nitrogenous base. This structure forms the double helix shape of DNA. Proteins (option A) are not the building blocks of DNA, but they are involved in various cellular functions. Lipids (option C) and carbohydrates (option D) are not the primary components of DNA. Overall, nucleotides are the fundamental units of DNA, making option B the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouse of the cell as they produce energy through the process of respiration. They contain enzymes responsible for converting nutrients into ATP, the energy currency of the cell. The nucleus (A) is responsible for storing genetic material, Golgi Apparatus (C) is involved in protein processing and packaging, and Chloroplasts (D) are responsible for photosynthesis in plant cells, not respiration.

Correct Answer: B

Rationale: The correct answer is B: Lipids. The plasma membrane is primarily composed of lipids, specifically phospholipids, which form a lipid bilayer. This structure provides the membrane with its selective permeability properties. Proteins are also present in the membrane, but they are not the primary composition. Carbohydrates are found on the outer surface of the membrane for cell recognition and signaling. Nucleotides are the building blocks of nucleic acids and are not a major component of the plasma membrane.

Correct Answer: D

Rationale: The primary function of the endoplasmic reticulum (ER) in a cell is the transport of materials. The ER consists of a network of membranes that help in the synthesis, folding, and transport of proteins and lipids. It plays a crucial role in the intracellular transport of materials between different cell compartments. This process ensures that newly synthesized proteins and lipids are properly transported to their respective destinations within the cell. The ER also serves as a site for the modification and packaging of proteins before they are transported to other organelles or secreted outside the cell. Therefore, the correct answer is D. Incorrect choices: A: Energy production - This is not the primary function of the ER. Energy production mainly occurs in mitochondria. B: Protein synthesis - While the ER is involved in protein synthesis, its primary function is the transport of materials. C: Waste removal - Waste removal is primarily carried out by lysosomes and peroxisomes in a cell, not the ER

Correct Answer: B

Rationale: The correct answer is B: Cell Membrane. The cell membrane serves as a selectively permeable barrier that controls the passage of substances into and out of the cell. It is composed of a phospholipid bilayer with embedded proteins that regulate the transport of molecules. The other choices are incorrect because: A: Vacuole - Vacuoles are membrane-bound organelles that mainly store water, ions, and nutrients. They do not control the passage of substances into and out of the cell. C: Nuclear Membrane - The nuclear membrane surrounds the nucleus and regulates the passage of molecules between the nucleus and the cytoplasm. It does not control the passage of substances into and out of the entire cell. D: Cytoplasm - Cytoplasm is the gel-like substance inside the cell that contains organelles. It does not directly control the passage of substances into and out of the cell; instead, it provides a medium for cellular activities to occur.