2.4.4) Cofactors, coenzymes and prosthetic groups

Key information required for this part of the enzyme topic for OCR A Level Biology

What are cofactors

Non-protein parts of an enzyme required for the enzyme to perform its function

What are coenzymes, what are they often derived from and give an example of one

Organic cofactors that bind temporarily to the enzyme to transfer chemical groups needed for the reaction; vitamins; vitamin B3 is required to make NAPD (needed for photosynthesis)

What is the function of inorganic ions, where are they often found and give an example of one

Inorganic cofactors that help the enzyme and substrate bind together by changing the shape of the active site; trace elements in our diet; Cl- is required for the amylase enzyme

What are prosthetic groups and give an example of one

Cofactors which bond permanently to an enzyme and are part of its structure; Zn2+ ions are part of carbonic anhydrase (in red blood cells)

What is precursor activation

Some enzymes are secreted in an inactive form (apoenzyme) which is activated by the addition of a cofactor (holoenzyme)

Why is precursor activation used

A safety mechanism: some enzymes may otherwise cause damage to the cells they are made in