Answer:
Correct answer is D: mitochondrion
Explanation:
In mitochondrion respiration takes place.
In this process, that occurs in presence of oxygen, energy is obtained from pyruvate. Glucose is a key product from food and has chemical energy stored. Pyruvate comes from glucose degradation in cytosol and gets into the mitochondrion. There, it is degraded and electrons are transported from a membrane protein to another one until they reach the oxygen and form H2O. While this occurs, a H+ (proton) gradient is generated at both sides of the internal mitochondrion membrane and this potential is finally used to synthesize ATP (available energy for the cell).
