WB page 50 - Enzymes are…

Proteins Biological Catalysts (speed up rxns

without being used up) Generally Specific (act on one type

of compound) Either catabolic (ab = a + b) or

anabolic (a + b = ab)Catabolism; Cut Anabolism; Add

Enzyme names

Enzymes are named by adding the suffix “-ase” to the substance they act upon.

E.g. Lipase (act on lipid), maltase (act on maltose), urease (act on urea)

Enzyme StructureThey have an

active site which attracts the

substrate(s) and position the

substrates to promote a reaction

Lock and Key HypothesisUsually only onetype of substrate molecule will fit into the active site of an enzyme.

Substrate = KeyEnzyme = lock

Maltose is made of two glucose molecules bonded together (1). The maltase enzyme is a protein that is perfectly shaped to

accept a maltose molecule and break the bond (2). The two glucose molecules are released (3). A single maltase enzyme can break in excess of 1,000 maltose

bonds per second, and will only accept maltose molecules.

Induced Fit model – partially flexible enzyme

The enzyme’s active site is not an exact fit for the substrate. The shape of the enzyme changes

when the substrate bind to the active site.

How do enzymes work?

Enzymes speed up rxns by lowering the activation energy- activation energy (AE) is the energy required before a rxn can occur. [“jumpstarting” the reaction]- can also be explained by an energy hill graph AE = energy needed to push the reactants over the energy barrier

Energy hill graph

DO NOW: Sketch this graph into your notebook

What affects how enzymes work?

Enzyme Cofactors Alter the shape of the enzyme’s active

site slightly to make active site more ‘reactive’

Enables substrates to ‘fit’ that might not have been able to without the cofactor

Cofactors can be ions or a vitamin e.g. amylase need Cl ion to convert

starch to maltose e.g. vit B2 important coenzyme in

cellular respiration.Organic cofactors = coenzymes