HESI A2 Biology Practice Test

Correct Answer: B

Rationale: Thymine is not present in RNA because thymine is a pyrimidine base found in DNA instead of RNA. RNA contains uracil as its complementary base to adenine, while DNA contains thymine. Adenine, uracil, and cytosine are all present in RNA, making them incorrect choices. Thymine is the only base not present in RNA, making option B the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Bacteria. Eukaryotic cells have a defined nucleus and membrane-bound organelles, which bacteria lack. Dogs, humans, and onions are all multicellular organisms that possess eukaryotic cells. Bacteria, being prokaryotic, do not have a distinct nucleus or membrane-bound organelles, leading to the conclusion that they do not have eukaryotic cells.

Correct Answer: D

Rationale: Failed to generate a rationale after 5 retries.

Correct Answer: D

Rationale: The correct answer is D: 206. The human adult skeletal system consists of 206 bones. This number includes bones of the skull, spine, rib cage, and limbs. The other choices are incorrect because: A) 412 is too high for the number of bones in the human body, B) 103 is too low and doesn't account for all bones, and C) "Over 300" is vague and doesn't provide an accurate count of the total bones in the human skeletal system.

Correct Answer: A

Rationale: Epithelial cells are correct to be classified as polarized because they have distinct apical and basal surfaces. The apical surface faces the external environment or a body cavity, while the basal surface is anchored to the underlying connective tissue. This polarity is essential for the specialized functions of epithelial cells, such as absorption, secretion, and transportation. Therefore, choice A is the correct answer. Choices B and C are incorrect because epithelial cells are not neutral and are not necessarily larger than other cells. Choice D is incorrect because epithelial cells do have unique characteristics that differentiate them from other cell types.