PSAT Reading Question 510: Answer and Explanation

Question: 510

How does the information in Figures 1 and 2 help make the author's case that Methanosphaera stadtmanae is helpful to humans, relative to many other similar bacteria and archaeal organisms?

• A. The figures show that pentose phosphate does not have the needed intermediates to carry out the development of methanol.
• B. The figures demonstrate that M. stadtmanae is genetically similar to the more common Methanobrevibacter smithii.
• C. The figures detail the chemical process whereby inflammatory bowel disease can be avoided.
• D. The figures show that M. stadtmanae lacks the necessary intermediates for most of the common energy pathways.

Correct Answer: D

Explanation:

(D) First, consider why the author says that Methanosphaera stadtmanae is beneficial to the host. In the first paragraph, he talks about how this species has a particularly restrictive energy metabolism, stating that "these unique energy conservation traits are what make Methanosphaera stadtmanae beneficial to its human host and not an opportunistic pathogen." Thus, we're looking for an answer choice from the figures that shows that this species conserves energy. Notice that for most of the pathways, Figure 1 says that at least some sort of intermediate is missing. In Figure 2, many of the boxes are black, meaning intermediates are missing. Thus, the answer is choice (D). Choices (A) and (B) aren't mentioned in the passage, and choice (C) isn't supported by the figures.