HESI A2 Biology Practice Test 2024

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.

Correct Answer: B

Rationale: The correct answer is B: 23 pairs. Humans have a total of 46 chromosomes, with 23 pairs. This is because we inherit one set of 23 chromosomes from each parent. Each pair consists of one chromosome from the mother and one from the father. Choices A, C, and D are incorrect because they do not align with the established fact that humans have 23 pairs of chromosomes. It's crucial to understand the basics of human genetics to grasp the correct answer in this case.

Correct Answer: B

Rationale: The correct answer is B: Eukaryotic. Animal cells are eukaryotic cells because they have a defined nucleus that houses the genetic material. This nucleus is surrounded by a membrane, along with other membrane-bound organelles like mitochondria and endoplasmic reticulum. Prokaryotic cells (Option A) lack a true nucleus and membrane-bound organelles. Plant cells (Option C) have similar characteristics to animal cells but also have additional features like a cell wall and chloroplasts. Bacterial cells (Option D) are prokaryotic cells and differ significantly from animal cells in structure and function.

Correct Answer: B

Rationale: The correct answer is B: Chloroplasts. Chloroplasts are the organelles responsible for photosynthesis in plant cells. They contain chlorophyll, the pigment that captures sunlight for photosynthesis. Mitochondria (A) are involved in cellular respiration, not photosynthesis. Ribosomes (C) are responsible for protein synthesis, not photosynthesis. Endoplasmic Reticulum (D) is involved in protein and lipid synthesis, not photosynthesis. Therefore, the correct answer is B because chloroplasts are specifically designed for photosynthesis in plant cells.