PSAT Reading Question 485: Answer and Explanation

Question: 485

Which of these gives the correct sequence of processes as described in the paragraphs in lines 11–24?

• A. Adenosine triphosphate is formed in the pineal gland from the reaction between natural melatonin and artificial adenosine.
• B. Adenosine and adenosine triphosphate stimulate the production of melatonin in the pineal gland.
• C. Adenosine and melatonin from the pineal gland cause energy to be released in the creation of adenosine triphosphate.
• D. Melatonin is released from the pineal gland as a result of detection of adenosine, which comes from the breakdown of adenosine triphosphate.

Correct Answer: D

Explanation:

(D) The first of these two paragraphs says that in a thermodynamically favorable reaction, adenosine triphosphate releases its phosphates and free energy, leaving just adenosine and inorganic phosphate. The next paragraph talks about how we have neurons that have evolved to detect the presence of adenosine and then to direct the pineal gland to secrete melatonin. This sequence is described by answer choice (D). Choice (A) is wrong because the pineal gland secretes melatonin, rather than forms adenosine triphosphate. Choice (B) is wrong because the detection of just adenosine triggers the melatonin response; the presence of adenosine triphosphate does not have this effect. Choice (C) doesn't work because the energy is released when adenosine triphosphate decomposes to adenosine and inorganic phosphate.