What role do coenzymes play in enzymatic reactions?

Coenzymes are organic molecules that are not proteins but work alongside enzymes to enhance their activity. Their primary role in enzymatic reactions is to assist by transferring functional groups, atoms, or electrons from one substrate to another. This transfer is crucial for the reaction to occur, as many enzymes require these coenzymes to function properly. For instance, in metabolic pathways, coenzymes like NAD+ and FAD are essential for oxidation-reduction reactions, where they carry electrons between different molecules, facilitating energy production and various biosynthetic processes.

The other options do not accurately reflect the role of coenzymes. While some molecules can act as substrates for enzymes, coenzymes themselves are not substrates; they support the enzyme's function. Furthermore, coenzymes are generally not tightly integrated into the enzyme structure; instead, they loosely associate and can be modified or released during the reaction. Lastly, coenzymes do not inhibit enzyme activity; rather, they are vital for catalysis and the progression of biochemical reactions, contrasting with inhibitors, which would impede activity. Therefore, recognizing the role of coenzymes in transferring functional groups is key to understanding their function in enzymatic reactions.