What are the primary hydrogen shuttles in the cellular respiration process?

NADH and FADH2 serve as the primary hydrogen shuttles during the process of cellular respiration. These molecules are crucial in transferring electrons and protons, derived from the catabolism of nutrients, primarily glucose. During glycolysis and the Krebs cycle (also known as the citric acid cycle), NAD+ is reduced to NADH, and FAD is reduced to FADH2, allowing them to carry high-energy electrons to the electron transport chain.

In the electron transport chain, the electrons from NADH and FADH2 are passed along a series of proteins, contributing to the synthesis of ATP through oxidative phosphorylation. This process generates a proton gradient across the inner mitochondrial membrane, which drives ATP synthesis as protons flow back into the mitochondrial matrix through ATP synthase.

Other options such as ATP and ADP play a role in energy transfer but are not primarily involved in shuttling hydrogen during respiration. Similarly, glucose and fructose are substrates for cellular respiration rather than carriers of hydrogen, and Acetyl-CoA and citrate are intermediates in metabolic pathways but do not function as hydrogen shuttles. Thus, NADH and FADH2 are vital for the efficient production of energy within cells via their role in