Question

melanocytes are skin cells that produce pigments and develop into a cancer known as melanoma. some cutaneous melanocytes have developed resistance to the drugs currently used to treat melanoma. as a result, researchers are investigating the effects of a new compound (drug x) on four different melanoma cell lines. researchers analyzed cell survival in two cell lines (figure 1) and oxygen consumption in the presence of drug x in all four cell lines (figure 2). figure 3 shows the proposed mechanism by which drug x affects cells. based on the information presented, which of the following best explains why the researchers measured oxygen consumption as an indication of the effectiveness of drug x? a oxygen provides the source of electrons for cellular respiration and is necessary for energy production. b oxygen consumption increases the mutation rate and causes cells to become abnormal melanocytes. c oxygen activates apoptosis, which results in the death of melanoma cells. d oxygen accepts electrons in oxidative phosphorylation, a process necessary for melanoma cell survival.

Explanation:

Melanoma cells (cancerous) rely on oxidative phosphorylation (a process using oxygen to accept electrons for ATP production) for survival. Figure 2 shows drug X reduces oxygen consumption in melanoma cell lines, linking oxygen consumption to their viability—so measuring it indicates drug X's effectiveness by targeting this essential process. Options A (general energy) is too broad, B (mutation/cancer causation) is irrelevant, C (apoptosis via oxygen) is unsupported; D directly connects oxygen's role in oxidative phosphorylation to melanoma survival, matching the context.

Answer:

D. Oxygen accepts electrons in oxidative phosphorylation, a process necessary for melanoma cell survival.