Enzymes — Biological Catalysts

Enzymes speed up reactions by lowering activation energy. They are not consumed in the reaction.

Key terms:

Active site — where substrate binds

Substrate — reactant that binds to enzyme

ES complex — enzyme-substrate complex

Cofactor — non-protein helper (metal ions)

Coenzyme — organic cofactor (vitamins)

Michaelis-Menten kinetics:

v = Vmax[S] / (Km + [S])

Km = substrate concentration at half-maximal velocity; lower Km = higher affinity

Vmax = maximum reaction velocity

Types of inhibition:

Competitive — inhibitor competes for active site; raises Km, Vmax unchanged; overcome with more substrate

Noncompetitive — binds allosteric site; lowers Vmax; Km unchanged; cannot be overcome

Uncompetitive — binds only ES complex; lowers both Km and Vmax

Allosteric regulation: Effectors bind sites other than the active site, changing enzyme shape and activity. Feedback inhibition = product inhibits its own pathway.

Reference:

Wikipedia: Enzyme

https://en.wikipedia.org/wiki/Enzyme