AP BIOLOGY

Detailed explanation-1: -Cytochrome c oxidase, the terminal enzyme of cellular respiration in mitochondria and many bacteria, reduces O2 to water. This four-electron reduction process is coupled to translocation (pumping) of four protons across the mitochondrial or bacterial membrane1; however, proton pumping is poorly understood.

Detailed explanation-2: -At the end of the electron transport system, the electrons are used to reduce an oxygen molecule to oxygen ions. The extra electrons on the oxygen ions attract hydrogen ions (protons) from the surrounding medium, and water is formed.

Detailed explanation-3: -NADH is the reduced form of the electron carrier, and NADH is converted into NAD+. This half of the reaction results in the oxidation of the electron carrier.

Detailed explanation-4: -In glycolysis, the six-carbon molecule glucose undergoes a range of chemical transformations, the electron carrier NAD+ is reduced by accepts two electrons and a hydrogen ion producing NADH.