When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

a. The pH of the matrix increases.

b. ATP synthase pumps protons by active transport.

c. The electrons gain free energy.

d. NAD + is oxidized.

a. The pH of the matrix increases is the correct answer.

Explanation:

When electrons flow along the electron transport chains of mitochondria, The pH of the matrix increases because the electron transport chain is forming a gradient of hydrogen ions in respects to the matrix and the inner membrane surface of the mitochondria.

The concentration of hydrogen ion outside is higher as compared to the matrix. Thus due to higher concentration of hydrogen ions outside creates lower pH and the pH of the matrix increases.