Enzymes

Bio C5

Anabolic reactions

-Reactions that build up/make molecules

Catabolic reactions

-Reactions that break down/destroy molecules

Metabolism

-Chemical processes that occur within a living organism in order to maintain life

-A combination of anabolic & catabolic reactions

Catalyst

-A substance that speeds up reactions without changing the produced substances

Metabolic pathway

-Sequence of enzyme controlled reactions

Specificity

-The particular reactions the enzyme catalyses

Substrate

-The molecule/s the enzyme works on

Products

-The molecule/s produced by the enzymes

Enzymes:

-Are proteins

-Substrate specific

-Reusable

-Needed in small amounts

-Are neither reactants nor products

-Make a reaction take place more easily

The induced-fit model

-Suggests that the active site is flexible and only assumes its shape (catalytic conformation) after substrate molecules bind to the site

Characteristics of enzymes:

-Only change the rate of reaction (not the equilibrium or end products)

-Specific to one particular region

-Present in very small amounts due to high molecular activity

-Rate of enzyme action is dependent on number of substrate molecules present

Coenzymes & cofactors:

Coenzymes:

-very small organic molecules

-associated with particular enzymes & are essential for their activity

-many coenzymes cannot be synthesised by animals, must be obtained from plants

-many are derived from vitamins

Cofactors:

-some enzymes require particular metallic cations (known as cofactors)

-examples: Cu 2+ & Mg 2+

Inhibitors:

-inhibitors are chemicals that reduce the rate of enzyme reactions

-usually specific & work at low concentrations

-block the enzyme, but do not usually destroy it

-examples: many drugs & poisons (inhibitors of enzymes in the nervous system)

Irreversible inhibitors:

-combine with the functional groups of the amino acids in the active site irreversibly

-examples: nerve gases & pesticides

Reversible inhibitors:

-can be washed out of the solution of enzyme by dialysis

-examples

What are the two mechanisms of inhibition?

-competitive & non-competitive

Competitive inhibition:

-Compete with the substrate molecules for the active site

-Resemble the substrate’s structure closely

*The inhibitors action is proportional to it’s concentration

Non-competitive inhibition:

-Inhibits by binding to the enzyme but NOT at the active site

-Not influenced by the concentration of the substrate

What is the allosteric site?

-Switches the enzyme on & off