HESI A2 Biology Practice Test

Correct Answer: B

Rationale: The correct answer is B because of osmosis. Saltwater has a higher concentration of solute than the egg, causing water to move out of the egg, leading to shrinkage. A is incorrect as the egg will lose water, not expand. C is incorrect as there will be a change due to osmosis. D is incorrect as an effect will occur.

Correct Answer: B

Rationale: The correct answer is B because of osmosis. Saltwater has a higher concentration of solute than the egg, causing water to move out of the egg, leading to shrinkage. A is incorrect as the egg will lose water, not expand. C is incorrect as there will be a change due to osmosis. D is incorrect as an effect will occur.

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: 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.

Correct Answer: A

Rationale: The correct answer is A: The nucleus. DNA is stored in the nucleus of a cell because it contains the genetic material that carries instructions for the cell's functions. The nucleus is specifically designed to protect and regulate access to the DNA. Ribosomes (B) are responsible for protein synthesis, not DNA storage. Endoplasmic reticulum (C) is involved in protein and lipid synthesis, but not DNA storage. Mitochondria (D) have their own DNA, but the majority of the cell's DNA is stored in the nucleus.