HESI A2 Biology Practice Test 2024

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.

Correct Answer: B

Rationale: During metaphase of mitosis, chromosomes align at the cell's equator, forming the metaphase plate. This alignment ensures that during anaphase, sister chromatids separate and move towards opposite poles. Prophase is characterized by chromosome condensation, telophase marks the end of nuclear division. Anaphase involves the actual separation of chromatids. Metaphase is the correct answer as it is the phase where chromosomes are precisely aligned for accurate distribution to daughter cells.

Correct Answer: B

Rationale: The correct answer is B: Glycolysis. This is the initial step in the metabolism of food to cellular energy because it involves the breakdown of glucose to produce ATP, the cell's energy currency. Glycolysis occurs in the cytoplasm and does not require oxygen. The Citric Acid Cycle (A) and Electron Transport Chain (C) occur after glycolysis in cellular respiration. Photosynthesis (D) is the process by which plants convert light energy into chemical energy, not the metabolism of food for cellular energy.

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: B

Rationale: The correct answer is B: Vacuoles (contractile). Contractile vacuoles are responsible for pushing excess water out of the cell through a process called osmoregulation. They maintain the cell's internal water balance by collecting and expelling water to prevent the cell from bursting due to osmotic pressure. Lysosomes (A) are involved in cellular waste disposal, mitochondria (C) are the powerhouse of the cell, and the nucleus (D) contains genetic material but does not play a role in expelling water from the cell.