Regarding inorganic cofactors, which is true?

• A. They are typically metal ions
• B. They are typically organic molecules
• C. They always come from vitamins
• D. They are always covalently bound to enzyme

Answer: (A)

Inorganic cofactors are metal ions that enzymes need to function. These ions—like magnesium, zinc, iron, and copper—serve as essential players in catalysis by stabilizing negative charges, helping orient substrates, or participating directly in redox chemistry. They are inorganic by nature, unlike organic cofactors (coenzymes), which are vitamin-derived molecules. They don’t have to come from vitamins; minerals from the diet can act as these cofactors. And they aren’t always covalently bound to the enzyme; many bind through noncovalent interactions, though some enzymes do have tightly bound prosthetic metal ions. So the statement that they are typically metal ions best captures the true, defining feature.