Coenzyme: Definition & Examples

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  • 0:00 Enzymes and Coenzymes
  • 0:55 Coenzymes
  • 2:45 Lesson Summary
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Lesson Transcript
Instructor: Jeremy Battista
Even the most simplistic organisms can be complex. There are many inner workings of individual cells that occur in order for us to survive. At times, the cells need help completing their tasks. This lesson explores cells co-workers or the coenzymes.

Enzymes and Coenzymes

Before we talk about coenzymes, it might be best to ask ourselves, 'What are enzymes and what do they do?' An enzyme is a protein, more importantly a catalytic protein. You may recall from a chemistry class that a catalyst is something that speeds up a reaction without actually being consumed in the reaction. Enzymes are those catalysts in our bodies.

Here we see an enzyme attaching to a substrate, including active site and ultimately the product from the reaction.

Enzymes attach to a substrate at an active sight and the reaction transforms the substrate. Enzymes account for many of the reactions that occur in our bodies. There are three characteristics of enzymes. One characteristic is to speed up a reaction. The second characteristic of an enzyme is that they work with only one particular substrate or reactant. The third is that enzymes are regulated from low to high activity. In fact, the reactions that they work with are somewhere in the ballpark of a million times faster than a regular cellular reaction on its own.


How do coenzymes fit into this idea of enzymes? Sometimes enzymes cannot complete the reaction on their own, they need help. They find help in the form of non-protein units called cofactors. These cofactors can bind to the substrate that the enzyme will react with or they can bind to the active site, or specific shape of the enzyme. Often these are inorganic, meaning they are compounds that do not contain carbon. These would include most metal ions. Metal ions are atoms with uneven numbers of protons and electrons. If the cofactor is indeed organic, containing carbon, we call it a coenzyme. Without the cofactor, the enzyme might have some trouble working with the substrate. The cofactor, or coenzyme, allows the reaction to happen quickly.

This is a prime example of an enzyme working with a cofactor.
Enzyme Cofactors

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