Coenzymes, Cofactors and the Chemistry They Supply
Amino acid side chains cannot do every chemical job, so enzymes recruit metal ions and small organic molecules to carry electrons, groups or single carbons. Many of those helpers are what vitamins are for.
What a learner can do afterwards
- Matches a coenzyme or organic cosubstrate to the electrons or chemical group it transfers.
- Distinguishes examples of metal-cofactor roles without assuming every metal performs redox chemistry.
- Links a vitamin shortage to its coenzyme and explains how dependent reactions may be impaired.
1 · Read
Cofactors extend protein chemistry. A cofactor is a non-protein helper; an organic cofactor is a coenzyme. Magnesium can stabilise phosphate charges, zinc can activate water, and iron can change oxidation state in redox reactions. Protein side chains also support proton transfer, charge stabilisation and some redox chemistry.
Vitamin B3 supplies a precursor for NAD, an electron carrier. Vitamin B1 supplies a precursor for thiamine pyrophosphate, or TPP, needed for pyruvate decarboxylation within pyruvate dehydrogenase. Deficiency can reduce coenzyme supply and impair dependent reactions, without stopping every reaction in the same broad class.
A cofactor-dependent enzyme's protein without its helper is the apoenzyme; the complete active form is the holoenzyme. Coenzymes may remain bound or bind and leave. They can change chemically and later be regenerated. NADH oxidation regenerates NAD+. Many coenzymes derive from vitamins, but not all do.
NAD+ accepts electrons to become NADH. FAD supports one-electron or two-electron transfers and is often enzyme-bound. CoA carries acyl groups, including acetyl groups. ATP transfers phosphoryl groups in kinase reactions. It is an organic cosubstrate; whether it is called a coenzyme depends on terminology.
Match each helper to its chemistry. A vitamin shortage can reduce a needed coenzyme's supply and impair reactions that depend on it.
Lesson, questions and flashcards written for this dataset.
Readings and flashcards written for this dataset.
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