HESI A2 Biology Practice Test

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.

Correct Answer: D

Rationale: The correct answer is D because all the choices - the pituitary gland, the thyroid gland, and the adrenal glands - are indeed components of the endocrine system. Each of these glands secretes hormones directly into the bloodstream to regulate various bodily functions. The pituitary gland controls other endocrine glands, the thyroid gland regulates metabolism, and the adrenal glands manage stress responses. Therefore, all of these glands play vital roles in the endocrine system. The other choices (A, B, C) are incorrect because they are all components of the endocrine system.

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: B

Rationale: Failed to generate a rationale after 5 retries.

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.