Enzymes

Characteristics of Enzymes1. Proteins2. Catalysts

a. Speed up chemical reactions without being used up

Structure1. An enzyme’s shape is very specific.

1. If changed, we call it…

DENATURED–Can no longer catalyze reactions– What kinds of things do you think could

denature a protein?

Denaturation

a. Disruption of protein structure by1. Heat: Break apart H bonds and disrupt

hydrophobic attractions 2. Acids/ bases: Break H bonds between polar

R groups and ionic bonds3. Heavy metal ions: React with S-S bonds to

form solids4. Agitation: Stretches chains until bonds

break

Applications of Denaturation

a. Hard boiling an eggb. Wiping skin with alcohol swab for injectionc. Cooking food to destroy E. coli

How do enzymes work?

1. Lower Activation Energy to speed up rates of reactiona. Reactions require energy to begin…

enzymes lower the amount of energy required.

Naming1. Often end in “–ase” 2. Prefix refers to what substance it causes

to reacta. Examples: maltase, sucrase,

protease, carboxypeptidase

Catalyzing Process

1. Unique 3-D shape determines which chemical reaction it catalyzes

2. Important Vocab:a. SUBSTRATE: A specific reactant that

an enzyme acts on.

2. Important Vocab (cont.):b. ACTIVE SITE: the region of the enzyme

where the substrate will bind

3. The enzyme and substrate bond to form the enzyme-substrate complex

substrate

enzyme

Active site

Enzyme-substrate complex

Lock and Key Model

+ +

E + S ES complex E + P

S P

P S

Enzymes are very specific!

1. An enzyme’s optimal temperature =highest rate of reaction

a. Most human enzymes work best at 35-40 ºC.

Optimum temperature

ReactionRate

Low High Temperature

TEMPERATURE

WATCH OUT!!!If the temperature gets too high, the enzyme may be

denatured!

pH (Acid/Base)

• The enzymes in your stomach will not work in your blood.

• Most of your enzymes work best around a neutral pH

Rate of Reaction

• enzyme lab…

Substrate ConcentrationIncreasing substrate concentration increases

the rate of reaction up to a certain point.a. Limited by enzyme concentration, why?

a. Maximum activity reached when all of enzyme combines with substrate

Substrate Concentration (cont.)

Maximum activity

ReactionRate

substrate concentration

Enzyme Inhibition

1. Inhibitors: cause a loss of catalytic activitya. May be competitive or noncompetitive

2. Competitive Inhibitiona. A competitive inhibitor

1. Has a structure similar to substrate2. Occupies active site

a. “Competes” with substrate for active site

3. Effects can be reversed by increasing substrate concentration

Competitive Inhibition Image

3. Noncompetitive Inhibition

a. A noncompetitive inhibitor1. Binds to the enzyme (not at active site) &

changes the shape of enzyme & active sitea. Substrate cannot fit altered active site

2. Effect is not reversed by adding substrate

Noncompetitive Inhibition Image