What is the purpose of the "sodium/potassium pump"

Correct Answer: D

Rationale: A concentration gradient is set up by the use of energy to move Na ions to where they are in greater concentration. This requirement for energy means choice B is wrong.

Correct Answer: C

Rationale: Guanine(G) must be matched to cytosine(C) and vice versa. Adenine(A) must match with thymine(T). In RNA, uracil(U) replaces thymine, while both bind to adenine. Hence U must be matched to A.

Correct Answer: A

Rationale: DNA exists in the nucleus. The other three are ribonucleic acids.

Correct Answer: D

Rationale: The skin is the primary organ of the integumentary system, serving as a protective barrier and regulating temperature.

Correct Answer: A

Rationale: Transitional epithelium is found in the urinary bladder.