ENZYMES

Enzymes Below is a listing which will help you to prepare for the quiz and lab on this material.

CONTENT TO KNOW:

I. ENZYME FUNCTION -

• Enzymes are biological CATALYSTS • Catalysts are things which speed up the rates of reactions • Enzymes are re-usable; they are not used up in the reaction itself

II. ENZYME STRUCTURE -

• Enzymes are PROTEINS • Building blocks (sub-units) of proteins are amino acids; therefore the

subunits of enzymes are also amino acids • ACTIVE SITES - the region of the enzyme which fits the substrate • SUBSTRATE - the molecule(s) to be worked upon by the enzyme • Enzyme-Substrate Complex - this is formed when the enzyme and

substrate are bound together; see picture below • Names of enzymes often end in ASE; "ase" is added to the substrate

name;  Example: Amylase - the enzyme that breaks down

STARCH

Click HERE for a picture of an enzyme

III. FACTORS AFFECTING ENZYME FUNCTION -

The shape of the protein can be changed by high heat or a change in pH - this is due to the fact that enzymes have a specific 3 dimensional shape held together by hydrogen bonds and other interactions between the amino acids;

• DENATURE - to denature an enzyme (protein) means to change its shape by high heat or pH; when the shape changes the ability of the enzyme to work is also changed

• OPTIMUM TEMPERATURE OR OPTIMUM pH - the temperature or pH at which the enzymes functions the best (optimally)

 Be sure that you can identify the optimum pH, optimum temperature, and maximum velocity on the graphs below

Click HERE for graphs

 Substrate Concentration & Enzyme Reaction Rate - Note that in the bottom figure, the velocity cannot increase beyond a certain substrate concentration, because all the active sites on the enzymes are filled already; it cannot go any faster once all the enzymes are already working

 Reaction Rate vs. Temperature - all enzymes have a temperature at which they function optimally (often body temperature)

 Reaction Rate vs. pH - all enzymes have a pH at which they function optimally (often neutral pH of 7)

IV. Examples of Enzymes -

• LACTASE - an enzyme which breaks down milk sugar which is called LACTOSE;  SUBSTRATE for LACTASE is LACTOSE; when lactose is broken

down by lactase, glucose and galactose are produced; (remember, lactose is a disaccharide, (2 sugar units linked together)

• LIPASE - an enzyme activated in the stomach; also found in saliva

 SUBSTRATE for LIPASE are LIPIDS (aka FATS)

• PEPSIN - an enzyme contained in the stomach; also found in saliva  SUBSTRATE for PEPSIN are PROTEINS

Note: Since LACTASE breaks down LACTOSE (a disaccharide composed of glucose and galatctose), we test for the presence of GLUCOSE using glucose test strips. Remember, if lactose is broken down by the enzyme lactase, then the presence of glucose will be detected .