HESI A2 Biology 2024

Correct Answer: A

Rationale: The correct answer is A: Centriole. Centrioles are cylindrical structures found in animal cells that play a key role in cell division by organizing microtubules of the mitotic spindle. Plant cells lack centrioles and instead use their microtubule organizing centers for cell division. B: Cytoplasm is incorrect as it is a universal component of all cells, including both animal and plant cells. C: Vacuole is incorrect as it is a large, membrane-bound organelle present in plant cells for storage, structure, and support. D: Golgi apparatus is incorrect as it is present in both animal and plant cells and is responsible for packaging and processing proteins for secretion.

Correct Answer: D

Rationale: The correct answer is D: Citric acid. Citric acid is not a component of DNA nucleotides. A DNA nucleotide consists of a simple sugar (deoxyribose), a nitrogen base (adenine, thymine, cytosine, or guanine), and a phosphate group. Citric acid is not part of the structure of DNA; it is a component of the citric acid cycle in cellular respiration. Therefore, it is not found in the nucleotide of DNA. The other choices (A, B, and C) are all components that make up a DNA nucleotide, making them incorrect options.

Correct Answer: B

Rationale: The correct answer is B: Pistil. The ovary is the female reproductive part of a flower, and it is located within the pistil. The pistil consists of three main parts: the stigma, style, and ovary. The ovary is the swollen base of the pistil that contains ovules, which develop into seeds after fertilization. A: Anther is the male reproductive part of a flower, responsible for producing and releasing pollen. C: Stamen is the male reproductive organ of a flower, consisting of the anther and filament. D: Calyx is the outermost whorl of a flower, consisting of sepals that protect the flower bud.

Correct Answer: C

Rationale: The correct answer is C: Osmosis. Osmosis is the process of water moving across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. In this scenario, the strong salt solution outside the bacteria creates a hypertonic environment, causing water to move out of the bacteria, leading to its shrinkage. Dehydration synthesis (A) is a process where molecules combine to form a larger molecule with the loss of water. Hydrolysis (B) is the opposite process where a larger molecule is broken down into smaller molecules by the addition of water. Isotonic transport (D) refers to the movement of molecules across a membrane to maintain equilibrium, not the specific process described in the question.

Correct Answer: C

Rationale: The correct answer is C: Order. Classification starts from the broadest category (Kingdom) to the most specific (Genus). Carnivora is an Order in the classification hierarchy, encompassing various families of carnivorous mammals, including dogs. Therefore, the correct classification for dogs within the Carnivora group is Order. Choices A, B, and D are incorrect because Kingdom refers to the highest taxonomic rank, Class is a level below Order, and Genus is a more specific category than Order.