Question

Use the Pyruvate Concentration Table to answer the question. The researcher adds a chemical to the cytosol at the one-hour mark. The full effect of the chemical can be observed at the two-hour mark. Which of the following hypotheses regarding the effect of the chemical is MOST reasonable?

Option 1: The chemical inhibits the carrier protein for pyruvate in the mitochondrial inner membrane.
Option 2: The chemical inhibits the carrier protein for glucose in the plasma membrane.
Option 3: The chemical inhibits the carrier protein for glucose in the mitochondrial inner membrane.
Option 4: The chemical inhibits the protein channels in the mitochondrial outer membrane.

Answer 1

The most reasonable hypothesis suggested is that the chemical inhibits the carrier protein for pyruvate in the mitochondrial inner membrane, because this would cause a direct change in the pyruvate concentration in the cytosol by preventing it from entering the mitochondria for further processing.

Step-by-step explanation:

To determine the most reasonable hypothesis regarding the effect of the chemical based on the Pyruvate Concentration Table, we should consider the likely points in the cellular respiration process that could be affected. If the pyruvate concentration inside the cell changes significantly between the one-hour mark and the two-hour mark after adding the chemical, we can infer the disruption is likely occurring at a step that directly affects pyruvate transport or metabolism.

Option 1 suggests the chemical inhibits the carrier protein for pyruvate in the mitochondrial inner membrane, which would prevent pyruvate from entering the mitochondria where it is further processed in the citric acid cycle. This would result in accumulated pyruvate in the cytosol, making this a plausible hypothesis.

Option 2 proposes inhibition of the carrier protein for glucose in the plasma membrane. However, this would affect glucose uptake into the cell, not directly affecting the cytosolic concentration of pyruvate, which is a downstream product of glycolysis.

Option 3, the inhibition of a carrier protein for glucose in the mitochondrial inner membrane, is not consistent with known cellular mechanisms as glucose is not transported into mitochondria.

Lastly, Option 4 suggests inhibition of the protein channels in the mitochondrial outer membrane, which is less specific to pyruvate transport compared to the specific carrier protein in the inner membrane. The outer membrane channels are generally more permeable and do not directly regulate pyruvate entry into the mitochondria.

Therefore, the most reasonable hypothesis is that the chemical inhibits the carrier protein for pyruvate in the mitochondrial inner membrane.