Oxidative phosphorylation and the electron transport chain

What is the main focus of oxidative phosphorylation in cellular respiration?

The main focus is to produce ATP from the oxidation of coenzymes such as NADH and coenzyme Q by transferring electrons through a series of acceptors in a controlled way.

What happens to NADH during oxidative phosphorylation?

NADH is oxidized to NAD⁺ by losing two electrons and a proton. This oxidation releases energy that can be used to pump protons across the mitochondrial membrane.

What is the final electron acceptor in the electron transport chain?

Oxygen acts as the final electron acceptor. It combines with electrons and protons to form water, and in this process, oxygen is reduced.

Why can't electrons be transferred directly from NADH to oxygen?

A direct transfer would release too much energy at once, which the cell couldn't capture efficiently. The electron transport chain allows stepwise energy release to do controlled work, like pumping protons.

What is the role of electron acceptors in oxidative phosphorylation?

Electrons are transferred from one acceptor to another (such as coenzyme Q and cytochrome C), releasing energy at each step. This energy is used to pump protons across the inner mitochondrial membrane.

What is the structure of the mitochondria relevant to oxidative phosphorylation?

Mitochondria have an outer membrane, an inner membrane with folds called cristae, the intermembrane space between them, and the matrix inside. The citric acid cycle occurs in the matrix, and the electron transport chain spans the inner membrane.

Where is FADH2 involved in oxidative phosphorylation?

FADH2 is reduced in the citric acid cycle and is used to reduce coenzyme Q to QH2, which then enters the electron transport chain. FADH2 enters slightly later than NADH and produces less ATP.

How is the proton gradient created during oxidative phosphorylation?

As electrons pass through the electron transport chain, energy is released and used to pump hydrogen protons from the matrix into the intermembrane space, creating a high concentration of protons outside the matrix.

What is the significance of the proton gradient?

The proton gradient stores energy as an electrochemical gradient. Protons naturally want to flow back into the matrix due to both charge and concentration differences, providing the potential energy needed to synthesize ATP.

How does ATP synthase produce ATP?

ATP synthase is a protein complex in the inner membrane. Protons flow down their electrochemical gradient through ATP synthase, causing its axle to spin. This mechanical rotation changes the enzyme’s conformation, allowing it to attach a phosphate group to ADP, forming ATP.

What analogy is used to describe ATP synthase?

ATP synthase is compared to a water turbine: just as flowing water turns a turbine to generate electricity, flowing protons turn the rotor in ATP synthase to generate ATP.

Where does the energy to produce most ATP in the cell come from?

Most energy comes from the reduction of coenzymes like NAD⁺ to NADH in glycolysis and the citric acid cycle. Oxidation of these coenzymes in oxidative phosphorylation drives ATP synthesis.

What is the overall summary of ATP production via oxidative phosphorylation?

NADH is oxidized to NAD⁺, electrons move through the electron transport chain, protons are pumped from the matrix to the intermembrane space, and the proton gradient drives ATP synthase to convert ADP and phosphate into ATP, which is the cell’s main energy currency.