Enzymes

Characteristics of Enzymes 1.Proteins 2.Catalysts a.Speed up chemical reactions without being used up

Structure 1.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 by 1.Heat: Break apart H bonds and disrupt hydrophobic attractions 2.Acids/ bases: Break H bonds between polar R groups and ionic bonds 3.Heavy metal ions: React with S-S bonds to form solids 4.Agitation: Stretches chains until bonds break

Applications of Denaturation a.Hard boiling an egg b.Wiping skin with alcohol swab for injection c.Cooking food to destroy E. coli

How do enzymes work? 1.Lower Activation Energy to speed up rates of reaction a.Reactions require energy to begin…enzymes lower the amount of energy required.

Naming 1.Often end in “–ase” 2.Prefix refers to what substance it causes to react a.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 ºC. Optimum temperature Reaction Rate 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 Concentration Increasing 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 Reaction Rate substrate concentration

Enzyme Inhibition 1.Inhibitors: cause a loss of catalytic activity a.May be competitive or noncompetitive

2.Competitive Inhibition a.A competitive inhibitor 1.Has a structure similar to substrate 2.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 inhibitor 1.Binds to the enzyme (not at active site) & changes the shape of enzyme & active site a.Substrate cannot fit altered active site 2.Effect is not reversed by adding substrate

Noncompetitive Inhibition Image