The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?
A) The pH within the thylakoid is less than that of the stroma.
B) The pH of the stroma is lower than that of the other two measurements.
C) The pH of the stroma is higher than that of the thylakoid space but lower than that of the cytosol.
D) The pH of the thylakoid space is higher than that anywhere else in the cell.
E) There is no consistent relationship.

Question

Quizplus · Accepted Answer

The pH within the thylakoid is expected to be lower (more acidic) than that of the stroma and cytosol. This is because the thylakoid space is the site of proton accumulation during photosynthesis, which generates an electrochemical gradient that is used to synthesize ATP. The stroma, on the other hand, has a pH that is closer to neutral, as it is the site of the Calvin cycle reactions. The cytosol has a slightly higher pH than the stroma, as it is more exposed to the external environment and needs to maintain a more neutral pH to prevent damage to the cell.

The PH of the Inner Thylakoid Space Has Been Measured