AP BIOLOGY

Detailed explanation-1: -Complex I (NADH-Ubiquinone Oxidoreductase) NADH is oxidized at the FMN center transferring 2 electrons to FMN, these electrons are then translocated across a 95 Å electron transfer pathway through the Fe–S centers to the ubiquinone binding site where they reduce ubiquinone to ubiquinol.

Detailed explanation-2: -Coenzyme Q (Ubiquinone) It is used to collect electrons from both Complex I and Complex II, and collects protons to form the fully reduced form ubiquinol, indicated as QH2. In the QH2 form it enters Complex III to transfer electrons to cytochrome c and pump protons into the intermembrane space of the mitochondrian.

Detailed explanation-3: -The NADH:ubiquinone oxidoreductase (Complex I), provides the input to the respiratory chain from the NAD-linked dehydrogenases of the citric acid cycle. The complex couples the oxidation of NADH and the reduction of ubiquinone, to the generation of a proton gradient which is then used for ATP synthesis.

Detailed explanation-4: -Complex I is the first enzyme of the respiratory chain. It oxidizes NADH, which is generated through the Krebs cycle in the mitochondrial matrix, and uses the two electrons to reduce ubiquinone to ubiquinol.