Prosthetic groups are best described as

Prosthetic groups are best described as

• A. Cofactors loosely bound to enzymes
• B. Nonprotein cofactors that are not bound
• C. Cofactors tightly bound to enzymes
• D. Substrates of the enzyme

Answer: (C)

Prosthetic groups are nonprotein cofactors that are tightly bound to enzymes and are required for activity. They stay attached to the enzyme during catalysis, forming part of the holoenzyme. This persistent, close association distinguishes them from cofactors that can dissociate or shuttle in and out of the enzyme’s active site. Prosthetic groups aren’t substrates; substrates are the molecules the enzyme acts upon and are transformed during the reaction, whereas the prosthetic group contributes chemical functionality that enables the reaction to proceed. Examples include the heme group in cytochromes and biotin in carboxylases, where the nonprotein component is integral to enzymatic function.

Prosthetic groups are nonprotein cofactors that are tightly bound to enzymes and are required for activity. They stay attached to the enzyme during catalysis, forming part of the holoenzyme. This persistent, close association distinguishes them from cofactors that can dissociate or shuttle in and out of the enzyme’s active site. Prosthetic groups aren’t substrates; substrates are the molecules the enzyme acts upon and are transformed during the reaction, whereas the prosthetic group contributes chemical functionality that enables the reaction to proceed. Examples include the heme group in cytochromes and biotin in carboxylases, where the nonprotein component is integral to enzymatic function.