Enzymes

The PROTEIN catalyst of life

Enzymes…. are protein substances that are necessary for:

1. The chemical reactions that occur in your body. Ex. Pepsin (enzyme) breaks protein down in the stomach.

2. Help to release energy in the form of ATP (adenine tri-phosphate) to the cells

3. Chemical Reactions Reactants- things that start the reaction

(what goes in).

Products- things that are produced (what comes out).

I. Enzyme VocabularyA. Enzymes end in –ase

Maltase binds to maltose Lactase binds to lactose Lipase breaks down fat Amylase is found in saliva

B. Catalyst: Substance that affects the RATE of a

chemical reaction WITHOUT BEING ALTERED

Because it is not altered, can do same thing over, and, over, and, over, and over…….

Enzymes are ORGANIC CATALYSTS

Enzyme Vocabulary cont.C. Substrate:

The substance upon which the enzyme reacts

D. Active site: Site where enzyme binds to

substrate

E. Denature: When enzyme’s shape is

altered due to: high temp strong acids or bases

II. How Do Enzymes Work?

DEMO

1. The enzyme has an active site which has a on its surface which has a very specific shape.

2. The enzyme and the substrate (what enzymes acts upon) temporarily join together forming the enzyme

substrate complex.

III. Importance of Enzyme Shape

A. Enzymes have specific shapesB. This means enzymes are specific to their substrateC. They will only attach to a substrate that “fits” their shapeD. If shape of enzyme is denatured, will it be able to bind to its substrate? NO!E. Two things can cause denaturing:

1. Temperature2. pH

IV. Enzyme-Substrate ComplexA. Formed when enzyme binds to substrateB. Very specific

C. Lock and Key Model1. Enzyme-substrate

complex often compared to a lock and key.

2. Active site on enzyme can only “FIT” or bind to a specific substrate

Example: Amylase will bind to starch, but not cellulose

Enzyme-Substrate (ES) Complex (lock and key model)

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

Enzyme is unchanged

Bellwork – do this in your journal

Tape the Lock and Key Model illustrating an enzyme into your journal.

1. Label the: Enzyme Substrate Active site Enzyme-substrate complex product

2. Is this reaction an example of digestion or synthesis? How can you tell?

Substrate

Enzyme Enzyme Enzyme

Substrate

Products

Digestion b/c there are 2 smaller products formed

Active Site

V. What factors influence Enzyme Action?

A. Remember, enzymes speed up reactionsB. What can affect the rate at which enzymes perform? 1.It’s shape!

a. Denaturing affects rate

C. The amount of enzyme and substrate!

1.Temperature - Enzyme shape and reaction rate: a. Enzymes have a specific temperature range at which they work best

EX. Human enzymes work best at 37°C

b. Temps not in the optimal range will cause enzymes to denature

c. Shape is altered, so reaction rates are SLOWED or stopped altogether

d. Reaction rates will DROP dramatically depending on how much denaturing of enzyme

Temperature vs. Reaction Rate

2. pH - Enzyme shape and reaction rate:a. Enzymes have a specific pH range at which

they work besti. EX. Most enzymes work best at pH 7ii. Where in the body would enzymes be optimal at a

low (acidic) pH? Why?

i. In stomach, this is because stomach acid has a low pH

b. pH not in the optimal range will cause enzymes to denature

c. Shape is altered, so reaction rates are SLOWED or stopped altogether

d. Reaction rates will DROP dramatically depending on how much denaturing of enzyme.

stomach

Small intestine

pH vs. Reaction Rate

3. Concentration - Enzyme amount and reaction rate:a. Enzyme rate also

depends on the amount of enzyme and substrate

b. Little enzyme, lots of substrate:

i. Slower ratesii. How can we speed

up the rate?1. Add more enzyme

until max. rate achieved.

Substrate Concentration vs. Reaction Rate