Is Vitamin A Coenzyme? 7 Facts (Read This First!)

Vitamins are organic molecules that are needed by the body in minimal quantities for normal metabolism. Let us see whether vitamins are coenzymes or not.

All vitamins do not act as coenzymes but most of the coenzymes are vitamins or derivatives of vitamins. The vitamins cannot be synthesized by the body hence they are obtained from food substances.

Let us discuss the facts about how and why vitamins are considered coenzymes.

Is a vitamin an example of a coenzyme?

Coenzyme is also known as co-substrate; they attach to the enzyme along with the substrate molecule at the beginning of the chemical reaction. Let us see different types of vitamins.

Vitamins are examples of coenzymes as they are organic molecules that are made up of vitamins or derivatives of vitamins. Coenzymes are vitamins that play a major role in metabolic pathways. The Coenzymes help in breaking down macromolecules into smaller molecules.

The vitamins are classified into two types:

  • Water-soluble vitaminsVitamin C, Vitamin B1, VitaminB2, Vitamin B5, Vitamin B6, Vitamin B7, Vitamin B3, and Vitamin B9, Vitamin B12
  • Fat-soluble vitamins- Vitamin A and Vitamin K

Vitamins also play a vital role in various processes like producing hormones, blood coagulation, vision, and maintaining bone density.

When vitamins are coenzymes?

Coenzymes bind to the active site of the enzyme and speed up the reaction. Let us see when vitamins are considered coenzymes.

Vitamins are considered as coenzyme when bind to the active site of the specific enzyme and helps in the catalysis of a reaction. They also function as an immediate carrier of electrons during the reactions.

Vitamins are required for the synthesis of vitamin-derived coenzymes; the vitamins are synthesized from fruits and vegetables.

How vitamins are coenzymes?

The transport of vitamins from the digestive tract to the bloodstream is done with the help of specific transport proteins. Let us see how vitamins act as coenzymes.

The vitamins get converted into coenzymes inside the cells. The vitamins; mainly the B complex vitamins serve as precursors for coenzymes which occur both in free form and bound forms that are liberated in the digestive tract.

The coenzyme gets attached to an apoenzyme by ionic, coordinate, and covalent bonds. The vitamin binds covalently to the apoenzyme directly to form a haloenzyme.

Why vitamins are coenzymes?

The vitamins are reconverted to their original form by the enzymes that are present inside the cells. Let us see why vitamins are considered as coenzymes.

Vitamins are considered as coenzymes because they bind to the enzyme before the other substrates bind to them.

The B-vitamin coenzymes function along with enzymes to transfer certain groups between the molecules as a result, proteins, fats, and carbohydrates are formed and utilized to release energy.

Examples of vitamins acted as coenzymes

There are many examples of vitamins acting as coenzymes, let us discuss a few examples in brief:

S.No Vitamins Coenzyme Function of coenzyme
1.Vitamin B1Thiamine PyrophosphateHelp in decarboxylation reactions
2.Vitamin B2Flavin Mononucleotide (FAD+)Help in the oxidation-reduction reaction
3.Vitamin B3Nicotinamide Adenine Dinucleotide (NAD+)Help in the oxidation-reduction reaction
4.Vitamin B6Pyridoxal PhosphateHelp in the transfer of the amino group
5.Vitamin B12MethylcobalaminHelps in intramolecular rearrangement
6.Vitamin B7BiotinHelp in the carboxylation reaction
7.Vitamin B5Coenzyme ACarries acyl groups
8.Vitamin B9TetrahydrofolateCarries formyl groups
Examples of vitamins as Coenzymes

Which vitamins are not coenzymes?

Vitamin-deficiency disease are caused due to the absence or shortage of vitamins. Let us see about the vitamins that do not act as coenzymes.

The vitamins that do not have coenzyme activity is vitamin E, which is also known as tocopherol. these are fat-soluble vitamins which act as antioxidants. The loose electrons or free radicals that damage the cells are destroyed by Vitamin E.The major source of vitamin E are Vegetable oil,nuts and seeds.

Difference between vitamin and coenzyme

Let us now discuss about the differences between Vitamins and Coenzymes

Vitamins Coenzymes
Definition Vitamins are organic molecules that are required by the body in small quantities.Coenzymes are organic molecules that help enzymes in catalytic activity.
TypesThey are two types: Water Soluble,Fat- soluble.They are of two types: Metabolite coenzymes, vitamins-derived coenzyme
SourceVitamins are not synthesized in the body but are derived from the dietCoenzymes are derived from vitamins
FunctionsVitamins help in cell function, growth, and developmentIt enhances the enzyme activity
Difference between Vitamins and Coenzymes


Coenzymes are organic molecules that are either vitamins or derivatives of vitamins that bind with enzyme and enhances their catalytic activity.

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