Which of the following is a cofactor and which is a coenzyme?
b. Tetrahydrofolate

Verified step by step guidance

1. Understand the difference between a cofactor and a coenzyme: A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity. Cofactors can be either inorganic (e.g., metal ions like Mg²⁺ or Zn²⁺) or organic. A coenzyme, on the other hand, is a specific type of organic cofactor that is loosely bound to the enzyme and often acts as a carrier of chemical groups or electrons during enzymatic reactions.
2. Identify the nature of tetrahydrofolate: Tetrahydrofolate (THF) is an organic molecule derived from folic acid (vitamin B9). It plays a critical role in the transfer of one-carbon units in metabolic reactions, such as DNA synthesis and amino acid metabolism.
3. Determine if tetrahydrofolate is a cofactor or coenzyme: Since tetrahydrofolate is an organic molecule that assists enzymes by transferring chemical groups (specifically one-carbon units), it is classified as a coenzyme.
4. Relate tetrahydrofolate to its biological function: Tetrahydrofolate is essential in processes like the synthesis of purines and thymidylate, which are necessary for DNA replication and repair. This further supports its role as a coenzyme.
5. Conclude: Based on its organic nature and its role in enzymatic reactions, tetrahydrofolate is a coenzyme, not a general cofactor.

Key Concepts

Cofactors

Cofactors are non-protein chemical compounds that assist enzymes in catalyzing reactions. They can be metal ions, such as zinc or magnesium, or organic molecules. Cofactors are essential for the activity of many enzymes, as they help stabilize enzyme-substrate complexes or participate directly in the chemical reaction.

Coenzymes

Coenzymes are a specific type of cofactor that are organic molecules, often derived from vitamins. They bind to enzymes and assist in the transfer of specific chemical groups during enzymatic reactions. Unlike cofactors, coenzymes are often altered during the reaction and need to be regenerated for continued enzyme activity.

Tetrahydrofolate

Tetrahydrofolate is a coenzyme derived from folate (vitamin B9) and plays a crucial role in the transfer of one-carbon units in various metabolic processes, including DNA synthesis and amino acid metabolism. It is essential for the proper functioning of enzymes involved in these pathways, making it a vital coenzyme in cellular metabolism.