Final answer:
The energy required for the transport of pyruvate into the mitochondrial matrix is provided by the proton-motive force, which is established by the action of the electron transport chain pumping hydrogen ions to create a concentration gradient.
Step-by-step explanation:
The correct option is D:
The transport of pyruvate into the mitochondrial matrix is an essential step for cellular respiration, specifically during the transition between glycolysis and the citric acid cycle.
This form of energy is derived from the gradient created by the electron transport chain (ETC) located in the inner mitochondrial membrane. Electron transport is the mechanism wherein electrons are moved through a series of electron carriers, leading to the pumping of hydrogen ions into the intermembrane space of mitochondria. Consequently, a proton gradient, or difference in hydrogen ion concentration, is established between the intermembrane space and the mitochondrial matrix.
The energy stored in this gradient, referred to as the proton-motive force, powers ATP synthase, an enzyme that catalyzes the conversion of ADP into ATP. Pyruvate is moved into the mitochondrial matrix using a carrier protein that harnesses this proton-motive force, illustrating how the chemiosmotic gradient is essential not only to ATP synthesis but also to the transport of crucial metabolic intermediates.