ENZYMES Nature’s Catalysts

Enzymes Proteins that act as biological catalysts to speed up chemical reactions

two or more substances combine to form one new substance SYNTHESIS two or more substances combine to form one new substance

SYNTHESIS A + B  AB Na + Cl2  NaCl Pb(IV) + O2  Pb2O4

when a substance breaks up into simpler substances DECOMPOSITION when a substance breaks up into simpler substances

Decomposition AB  A + B NaCl  Na + Cl2 Pb2O4  Pb + O2

General Formula for Reactions A + B  C Reactants yields Products

Enzymes Identify many enzymes by the suffix –ase: helicase (unzips DNA) lactase (breaks down lactose) peptidyl transferase (forms peptide bonds in polypeptides)

Enzymes speed up biochemical reactions by lowering the activation energy of reactions that would normally happen anyway.

The material that the enzyme works on. Substrates The material that the enzyme works on.

The special fold in the enzyme where the reaction happens Active Sites The special fold in the enzyme where the reaction happens

Competitive Inhibition When something besides the substrate blocks the active site

Competitive Inhibition Inhibitors—reduce the productivity of enzymes as seen to the right with herbicides. The body uses enzymes to control metabolic pathways.

Non-Competitive Inhibition When a molecule binds to another spot on the enzyme causing it to change shape and become inactive

Enzymes Enzymes bind substrates (enzyme reactant) into active sites (pocket or groove on enzyme). While the enzyme and the substrate are joined, the enzyme catalyzes the reaction and converts the substrate to the product(s).

Enzymes The most classic example an enzymatic reaction is the hydrolysis of sucrose (table sugar) into glucose and fructose.

Enzymes Another look…

Factors Afecting Enzyme Activity Temperature pH Enzyme Concentration Substrate Concentration

Effects on Enzyme Activity Rate of Enzyme Activity is influenced by: Substrate concentration (more substrate = more activity until saturation) Temperature (higher temperature = more activity until the enzyme’s protein denatures)

Effects on Enzyme Activity Rate of Enzyme Activity is influenced by: pH (usually in range of 6-8 for humans) Inhibitors (reduce activity by binding or changing shape of active sites) Alkaline Intestine Acidic Stomach

Enzymes: Fun Facts Enzymes work quickly—about 1000 substrates are taken in and converted every second.