Cofactors and coenzymes

[Bad Student]

There seem to be multiple definitions of coenzymes and cofactors in Nature of Biology and Biozone.

Nature of Biology defines cofactors as non-protein parts of an enzyme and coenzymes as organic cofactors.

Biozone defines cofactors as additional non-protein components of an enzyme with permanently attached cofactors called prosthetic groups and temporarily attached cofactors called coenzymes. But it also adds that coenzymes often refer to any organic cofactor.

Which definition is the official VCAA sanctioned definition?

[alondouek]

I don't think there is a official VCAA definition haha!

Wikipedia's definition is very similar to the one taught to me (LOL my teacher plagiarised Wikipedia):

A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity.

That's pretty much as detailed a definition as you need for VCE biology.

EDIT:

Cofactors can be classified depending on how tightly they bind to an enzyme, with loosely-bound cofactors termed coenzymes and tightly-bound cofactors termed prosthetic groups

Also Wiki, also perfectly adequate

[Bad Student]

What about coenzymes?

[alondouek]

Fixed my initial post to include 'em

[psyxwar]

I'm pretty sure coenzymes refer to organic molecules that assist enzyme function (for example vitamins), whereas cofactors refer to inorganic substances that assist enzyme function (for example ions).

[alondouek]

Yep, that's correct too (IIRC)

[Bad Student]

This is the problem I had in the first place. There are two definitions.

[alondouek]

This is the problem I had in the first place. There are two definitions.

Well not really, it's still a separate definition for coenzymes and cofactors:

I'll try and summarise everything for you:

Cofactors are inorganic non-protein chemical compounds that bind to the protein to assist it in performing its specific biological function (as an enzyme)

Coenzymes are organic 'cofactors'. Organic cofactors that bind loosely to the protein are termed 'coenzymes', while organic cofactors that are tightly bound to the protein are termed 'prosthetic groups'.