Please answer one of the following throughly. At what metabolic point can pyruvate be considered to be fully oxidized?

Please answer one of the following throughly.

At what metabolic point can pyruvate be considered to be fully oxidized? Explain. Use images if possible and explain

What is the direct energy source for forming the proton gradient? Explain.

 Describe the electron transport mechanism. What is the initial substrate? What is the final product? How many carriers? How many complexes?