What is the primary function of cofactors?

Step 1: Analyze the question The question asks about the main role of cofactors in biology, specifically in relation to enzymes.

Step 2: Explain the concept Many enzymes cannot work properly on their own. They need extra non-protein helpers called cofactors. These can be:

• Metal ions, such as Mg²⁺, Zn²⁺, Fe²⁺ and Ca²⁺
• Coenzymes, which are organic molecules, usually derived from vitamins. Examples are NAD⁺, FAD and coenzyme A.

Cofactors help the enzyme bind its substrate, take part in the reaction (for example by carrying electrons or chemical groups), or keep the enzyme's active site in the right shape. An enzyme without its cofactor is called an apoenzyme (inactive), while the enzyme with its cofactor is a holoenzyme (active).

Step 3: Check each option

• A. To aid in enzyme function: Correct. This is exactly what cofactors do.
• B. To synthesize enzymes: Wrong. Enzymes are proteins made at the ribosomes, following instructions from DNA and mRNA, not by cofactors.
• C. To inhibit enzymes: Wrong. That is the job of inhibitors (competitive and non-competitive), not cofactors.
• D. To break down old enzymes: Wrong. Old or damaged proteins are broken down by proteases and the cell's recycling systems.

Step 4: Answer The correct option is A. To aid in enzyme function.

Exam tip: Remember "Cofactor = Co-worker." A cofactor is a helper that works alongside the enzyme. Also remember the formula: Apoenzyme + Cofactor = Holoenzyme (active). Do not confuse cofactors with inhibitors, which do the opposite.