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: DNA. DNA, or deoxyribonucleic acid, is the molecule that stores the genetic code for each person. It is located in the cell nucleus and organized into structures called chromosomes. DNA contains the instructions for building and maintaining an organism, including traits and characteristics. RNA (choice A) is involved in protein synthesis but does not store the complete genetic information. The nucleus (choice C) is the cellular organelle where DNA is located, not the genetic code itself. Chromosomes (choice D) are made up of DNA and proteins and contain the genetic material in a condensed form. Therefore, the correct choice is DNA as it is the primary storage location for the genetic code.

Correct Answer: C

Rationale: The correct answer is C: 4. Mitosis consists of four phases: prophase, metaphase, anaphase, and telophase. In prophase, chromosomes condense. In metaphase, chromosomes align at the cell equator. In anaphase, sister chromatids separate and move to opposite poles. In telophase, the nuclear envelope reforms. Choices A, B, and D are incorrect because mitosis is a complex process that involves more than 2 or 3 phases.

Correct Answer: B

Rationale: In meiosis, sperm and egg cells produce haploid gametes with half the number of chromosomes as the parent cell. Since humans have 46 chromosomes in each somatic cell, sperm and egg cells produce 23 chromosomes each in meiosis. This ensures that when fertilization occurs, the resulting zygote has the correct diploid number of chromosomes. Choice A (46) is incorrect because somatic cells have 46 chromosomes, not gametes. Choice C (45) and D (24) are incorrect because they do not represent the correct haploid number of chromosomes produced in meiosis.

Correct Answer: C

Rationale: The correct answer is C: Mitochondria. Mitochondria are the site of cellular respiration in eukaryotic cells. Here's the rationale: 1. Mitochondria contain enzymes involved in the various stages of cellular respiration. 2. The inner membrane of mitochondria has folds called cristae, which provide a large surface area for aerobic respiration. 3. ATP, the energy currency of the cell, is produced in the mitochondria during cellular respiration. 4. Nucleus (A) houses the genetic material, not involved in cellular respiration. Chloroplasts (B) are found in plant cells and are responsible for photosynthesis, not respiration. Ribosomes (D) are involved in protein synthesis, not cellular respiration.