HESI A2 Biology Practice Test

Correct Answer: B

Rationale: To focus an image using a compound microscope, adjusting the fine adjustment is correct as it allows for precise focusing when switching magnifications. Coarse adjustment is only used initially to bring the specimen into view, while the stage adjustment is used to center the specimen. Therefore, B is correct as it ensures clear and sharp image focus without unnecessary readjustments. Choices A and C are incorrect as they do not address the specific need for precise focusing when changing magnifications, leading to potential blurriness or loss of focus in the image.

Correct Answer: B

Rationale: Correct Answer: B - Glycolysis occurs in the presence of Oxygen. Rationale: 1. Glycolysis is the initial step in cellular respiration and takes place in the cytoplasm of cells. 2. It does not require oxygen to start but can occur in both aerobic and anaerobic conditions. 3. In the presence of oxygen, the pyruvate produced from glycolysis can enter the citric acid cycle for further ATP production. Summary: A: Incorrect - Glycolysis can occur in the presence of oxygen. C: Incorrect - Fermentation is a separate process from glycolysis. D: Incorrect - Anaerobic respiration involves further steps after glycolysis.

Correct Answer: A

Rationale: The correct answer is A: It controls the substances entering and leaving the cell. The cell membrane acts as a selective barrier, regulating the passage of molecules in and out of the cell. It does this through various mechanisms such as protein channels and pumps. This function is crucial for maintaining cellular homeostasis and ensuring the cell's survival. Summary: - B: It maintains the cell's shape: The cell membrane does contribute to the cell's shape but this is not its primary function. - C: It controls the substances entering the cell: This is partially correct, but the cell membrane also controls substances leaving the cell. - D: It supports the cell's structures: While the cell membrane provides some structural support, its main function is controlling the movement of substances.

Correct Answer: A

Rationale: The correct answer is A: Adenine. Adenine is a nucleotide base that consists of two fused carbon rings, making it a purine base. The two rings in adenine are essential for its structure, function, and hydrogen bonding with thymine in DNA. The other choices, B, C, and D, are all pyrimidine bases, which have only one carbon ring. Therefore, adenine is the only base among the options that has two carbon rings, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D because in DNA, adenine (A) always pairs with thymine (T), forming two hydrogen bonds. This is known as complementary base pairing, essential for DNA replication and maintenance. Options A, B, and C are incorrect as they do not demonstrate the complementary base pairing rule observed in DNA. Option A (A and G) is incorrect because adenine pairs with thymine, not guanine. Option B (A and C) is incorrect because adenine pairs with thymine, not cytosine. Option C (A and A) is incorrect because in DNA, adenine always pairs with thymine, not with itself.