Final answer:
NADH produced in the cytosol is transported to the mitochondrion via indirect shuttle systems, and not through direct channels or transporters. FADH2 is the compound uniquely produced in the Krebs cycle during glucose catabolism. Electrons move through the electron transport chain leading to ATP synthesis.
Step-by-step explanation:
The movement of NADH from the cytosol into the mitochondrion does not occur via a ligand-gated channel, membrane permeability, or an NADH specific channel. Instead, the transfer of electrons from cytosolic NADH into the mitochondria involves shuttle systems such as the malate-aspartate shuttle or the glycerol phosphate shuttle since the mitochondrial membrane is impermeable to NADH. These shuttle systems transport the high-energy electrons of NADH across the mitochondrial membrane indirectly.
Krebs cycle generates several compounds including ATP, NADH, and FADH2, but not NADPH, which is produced in other metabolic pathways such as the pentose phosphate pathway. During glucose catabolism, FADH2 is indeed a molecule that is produced exclusively in the Krebs cycle (also known as the citric acid cycle or TCA cycle).
The function of an electron in the electron transport chain is to move along a series of protein complexes and mobile carriers like CoQ and cytochrome c, leading to the eventual reduction of oxygen to water. This movement is coupled to the pumping of hydrogen ions across the mitochondrial membrane, thereby generating a proton gradient used for ATP synthesis through oxidative phosphorylation.