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Question

Difficulty: MediumDrawing Logical Inferences from Passage Premises

Passage:
In abyssal benthic ecosystems, hydrothermal vent archaea rely on chemolithoautotrophy, oxidizing reduced sulfur compounds to fix inorganic carbon in total darkness. Recent biochemical studies of Pyrococcus isolates from the Mid-Atlantic Ridge demonstrate that these microorganisms express modified hydrogenase enzymes whose catalytic efficiency peaks only at hydrostatic pressures exceeding 30 megapascals (MPa). When cultured at atmospheric pressure (0.1 MPa) while maintaining identical temperature and nutrient concentrations, the enzymatic turnover rate drops by over 90 percent due to structural destabilization of the enzyme's active site. Furthermore, while surface-dwelling sulfur-oxidizing bacteria utilize heat-shock proteins to maintain enzyme integrity during thermal spikes, Pyrococcus isolates lack the genes encoding these specific heat-shock chaperones, relying instead on pressure-induced conformational rigidity to prevent thermal denaturation.

Statement: Based on the passage, Pyrococcus enzymes are more vulnerable to thermal denaturation when exposed to thermal spikes at atmospheric pressure than when exposed to the same thermal spikes under high hydrostatic pressure.

Answer: Answer

Answer

True
The statement logically follows from the premises in the text. The passage establishes that Pyrococcus isolates do not possess heat-shock chaperone genes and instead rely entirely on pressure-induced conformational rigidity to guard against thermal denaturation. At atmospheric pressure, hydrostatic pressure is insufficient to induce this rigidity, resulting in structural destabilization. Consequently, during a thermal spike at atmospheric pressure, the enzymes lack both chaperones and pressure-induced rigidity, rendering them more vulnerable to thermal denaturation than they would be under high hydrostatic pressure.

Step-by-Step Solution

1
Identify the mechanism that protects Pyrococcus enzymes from thermal denaturation.
The passage specifies that Pyrococcus isolates lack heat-shock chaperones and depend on pressure-induced conformational rigidity to prevent thermal denaturation.
Understanding the protective mechanism is necessary to evaluate enzyme stability under different physical conditions.
2
Analyze the structural state of the enzymes at atmospheric pressure.
At atmospheric pressure (0.1 MPa), pressure-induced conformational rigidity is lost, causing structural destabilization.
Determining whether protective rigidity exists at low pressure establishes the enzyme's baseline vulnerability.
3
Deduce relative vulnerability to thermal denaturation under atmospheric versus high hydrostatic pressure.
Because Pyrococcus lacks heat-shock chaperones and loses pressure-induced conformational rigidity at atmospheric pressure, its enzymes are more susceptible to thermal denaturation at atmospheric pressure than under high hydrostatic pressure.
Linking the absence of pressure-induced rigidity to increased vulnerability during thermal spikes validates the statement as a necessary logical inference.

Key Concept

Drawing necessary logical inferences from explicit passage premises.
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Drawing Logical Inferences from Passage Premises