Define coenzyme and give an Example, Coenzyme NAD +, ATP

Define coenzyme and give an Example

Define coenzyme and give an example coenzyme (often also a coenzyme) is a non-proteinaceous component of enzymes. It helps enzymes to catalyze (accelerate) reactions. This is possible because the coenzyme binds to the enzyme for a short time.

If it is a non-covalent (not fixed) bond, you call the coenzyme a cosubstrate . When a coenzyme binds covalently (tightly) to an enzyme, you call it a prosthetic group .

Coenzymes, therefore, take an active part in the enzyme reaction. In contrast to an enzyme, the cosubstrate and prosthetic group change during the reaction. Therefore, they have to be renewed after the reaction.

Coenzymes often serve as electron donors or acceptors in redox reactions. But you can also transfer certain chemical groups such as phosphate groups to other molecules.

Coenzymes definition

Coenzymes help enzymes catalyze reactions by attaching to the enzyme for a short period of time. Coenzyme is an umbrella term and can be divided into cosubstrate and prosthetic group.

Define coenzyme and give an Example, Coenzyme NAD + , ATP

Coenzyme and cofactor

Coenzymes and cofactors are not the same. Cofactor (also cofactor or English cofactor) is an umbrella term. It includes inorganic components such as metal ions and coenzymes . With metal ions are meant, for example, zinc, iron and copper ions. You can further subdivide coenzymes into cosubstrates and prosthetic groups .

Proesthetic group

Prosthetic groups bind covalently to an enzyme. If the prosthetic group is bound to an enzyme, you call it a holoenzyme . Otherwise, you call the enzyme an apoenzyme .

The substrate can only bind to the holoenzyme. So without the prosthetic group, the enzyme would not be able to catalyze the reaction. The prosthetic groups are often chemically altered during the reaction. Therefore, they have to be regenerated (renewed) after the reaction.

A typical example of a prosthetic group is FAD (flavin adenine dinucleotide). FAD is usually reduced to FADH 2 during the enzyme reaction . Both are important components for a functioning metabolism.


Cosubstrates bind non-covalently to an enzyme. Again, you call the enzyme holoenzyme if the cosubstrate is bound to the enzyme. If there is no cosubstrate bound to the enzyme, you call it an apoenzyme .

Cosubstrates can accept or release electrons, protons or functional groups. Therefore, they also change during the reaction and have to be renewed. This usually happens in a subsequent reaction. The renewed cosubstrates can then bind to the enzyme again.

Cosubstrates therefore behave more like substrates and not like enzymes: They bind to the enzyme together with the substrate and result from the reaction in a different way. So you can also easily remember the name Cosubstrat.

Coenzyme ATP

The coenzyme q10 produces the majority of ATP (adenosine triphosphate). ATP serves all living beings as a universal supplier of energy. ATP provides our body with a lot of energy every day. It plays an important role in metabolic processes such as glycolysis or gluconeogenesis.

ATP is a coenzyme (more precisely: a cosubstrate) that releases phosphate groups. A lot of energy is stored in the chemical bonds of the triphosphate unit. By splitting off a phosphate group, a lot of energy is released, which your body can then use for muscle contraction, for example.

Coenzyme NAD +

NAD + (nicotinamide adenine dinucleotide) is involved in many redox reactions of the metabolism as an electron acceptor . So it takes electrons. In addition, the NAD + is also a proton acceptor. So it takes two electrons and two protons. This NAD + to its redox NADH / H + reduced NADH / H + then releases the electrons and protons directly to the respiratory chain . NADH / H +  is oxidized again to NAD + . In the respiratory chain, the electrons and protons are then used, for example, for ATP production.

Coenzymes and Vitamins

It is very important that you get various vitamins through your diet. One of the reasons for this is that some coenzymes can only be produced by your body with the help of vitamins. This is the case, for example, with the coenzyme NAD + . Your body can only make it through vitamin B3 (niacinamide). You can find this in foods like fish, peanuts or mushrooms, for example.

FAD (Flavin Adenine Dinucleotide) is another example of a coenzyme that your body cannot make without the help of a vitamin. In order for FAD to be synthesized in your body, you need to consume vitamin B2 (riboflavin). You can find this in foods like milk, fish, or whole grain bread. FAD plays an important role in cell respiration and is therefore essential for a functioning metabolism.% You want to know how cell respiration works?  Then take a look at our video! % Thumbnail cell respiration

Define coenzyme and give an Example, Coenzyme NAD +, ATP

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