XVII. Enzymes: Special proteins

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

2. http://bcs.whfreeman.com/thelifewire/content/chp06/0602001.html

A. Function of enzymes: act as catalystscatalysts (which speed up chemical reactions)

B. Enzymes are specificspecific to the substrates on which they work.

C. Substrate—the reactant (substance) on which the enzyme works

D. Enzymes remain completely unchangedunchanged by the reaction.

E. Factors affecting the rate at which an enzyme can work:

1. temperature

2. pH

3. concentration (of enzyme and of substrate)

http://www.phschool.com/science/biology_place/labbench/lab2/temp.html

F. Enzymes work through a method called the Lock-and-Key MethodLock-and-Key Method.

substrates

enzyme enzyme-substrate complex

(with active site-

where action takes place)

product

enzyme

Lock-and-Key

G. Enzymes’ names end in

-ase.

Example: catalase• It catalyzes the decomposition (break-down)

of hydrogen peroxide into water and oxygen.

2H2O2 2H2O + O2 hydrogen peroxide water + oxygen

Additional notes on catalase:• One molecule of catalase can break down 40 million

molecules of hydrogen peroxide each second. • Hydrogen peroxide is a harmful byproduct of

certain cellular processes in organisms. Catalase is an enzyme that breaks down hydrogen peroxide. Cells make catalase in order to convert the hydrogen peroxide into harmless substances.

Reference for last two slides: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Enzymes.html (Found 9-15-08)

Example: carbonic anhydrase• It is found in red blood cells where it

catalyzes the reaction: CO2 + H2O H2CO3

carbon dioxide + water carbonic acid

Additional notes on the enzyme carbonic anhydrase:

• It enables red blood cells to transport carbon dioxide from the tissues to the lungs.

• One molecule of carbonic anhydrase can process one million molecules of CO2 each second.