Non-protein helpers such as metal ions and vitamins needed for enzyme activity.
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Many enzymes need non-protein helpers to function. Cofactors are inorganic ions such as Zn2+, Mg2+ and Fe2+, while coenzymes are organic molecules such as NAD+, FAD and coenzyme A that often carry electrons or chemical groups between reactions. An active enzyme made of protein plus its cofactor is called a holoenzyme, and the protein part alone is the apoenzyme. Many coenzymes are derived from vitamins, so a dietary deficiency can impair several enzymes at once. Tightly bound prosthetic groups are a special class of cofactor that remains attached throughout catalysis.
Key ideas: Cofactors are non-protein helpers needed for activity: metal ions (Zn2+, Mg2+, Fe2+, Cu2+) or organic coenzymes (NAD+, FAD, coenzyme A, many derived from B vitamins). An enzyme without its cofactor is an apoenzyme, with it a holoenzyme. Coenzymes often carry electrons or groups: NAD+ accepts hydride, giving NADH.
Common mistakes and connections: A mistake is calling every cofactor a coenzyme; coenzymes are organic only. Prosthetic groups are tightly or covalently bound, while coenzymes often bind loosely and act as cosubstrates. Vitamin deficiency causes disease via missing coenzymes. Links to vitamins and redox steps in respiration.
Roughly one third of enzymes need a metal ion cofactor such as Zn, Mg or Fe, while many others rely on organic coenzymes such as NAD+ derived from vitamins. The interactive lesson shows this as a live animation or chart.
NAD+ is built from niacin, or vitamin B3, and shuttles electrons between metabolic enzymes.
Non-protein helpers such as metal ions and vitamins needed for enzyme activity.
Cofactors and Coenzymes is a advanced topic in Biochemistry, Environment & Industry. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Biochemistry, Environment & Industry first: Enzymes, Active Site, Lock and Key vs Induced Fit.
The next topics in Biochemistry, Environment & Industry are Vitamins and Hormones.
Yes. The interactive lesson includes a self-check question on Cofactors and Coenzymes, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.
Cofactors and Coenzymes is topic 15 of 127 in Biochemistry, Environment & Industry.
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