enzymes

[nessi]

why do enzymes remain unchanged after a reaction and what evidence is there to prove this?

[Robb Phoenix]

Enzymes are biological catalysts.
A catalyst is any substance which alters the rate of a chemical reaction without undergoing any changes itself. The concept of catalysis fairly old,universally agreed upon and used in many commercial processes for example the Haber's process for preparation of ammonia.
A catalyst undergoes a reaction but it forms itself back in the end.
eg....
Chlorine free radicals in the break down of ozone. These radicals are formed by the action of ultraviolet radiation on chlorofluorocarbons (CFCs). They react with ozone to form oxygen molecules and regenerate the catalyst radicals. This process destroys the thin layer of stratospheric ozone.

Cl� + O3 → ClO� + O2
ClO� + O� → Cl� + O2

[Peter Pedant]

Yeah good answer from Robb

why do enzymes remain unchanged...

Because they are bioloigcal catalysts

If they were changed they would be co-factors or substrates, and as such couldnt work in the way they are designed to.

Evidence to prove this - always acive - and so if ou separate out the reactants which are always smaller so you could do this by utra fiters,
the activity persists.

Funnily enought the guy has just died - lst week - obituary - who popularised the surprising idea that enzymes have evolved into the most perfect forms and can't be bettered.