Final answer:
FAD (Flavin adenine dinucleotide) is the riboflavin coenzyme involved in catabolic reactions of energy metabolism, where it plays a central role in oxidation-reduction reactions and energy extraction from sugars.
Step-by-step explanation:
The riboflavin coenzyme that participates in catabolic reactions of energy metabolism is a. FAD (Flavin adenine dinucleotide). FAD is a crucial coenzyme derived from vitamin B2, also known as riboflavin. It plays a significant role in oxidation-reduction reactions within the cell, particularly during the catabolism of glucose. FAD is tightly associated with proteins, forming flavoproteins, and facilitates the extraction of energy from sugars by accepting electrons and hydrogen atoms (H+).
FAD exists in two states: the oxidized form (FAD) and the reduced form (FADH₂). The process of reduction involves the addition of two hydrogen atoms to FAD, forming FADH₂. This reaction is crucial in pathways such as the Krebs cycle, where FADH₂ is produced and later utilized in the electron transport chain to generate ATP.
Although similar in function to NAD+ (Nicotinamide Adenine Dinucleotide), FAD is considered more versatile because it can participate in various types of oxidation mechanisms. It is also distinct from ATP, which serves primarily as the cellular currency for energy, and TPP (Thiamine pyrophosphate), which is another type of coenzyme.