Enzymes

Enzymes

•Enzymes: are proteins made of amino acids.

-Catalyst: they speed up chemical reactions & lower the activation energy.

-Reusable: remain unchanged after the reaction

-specific: there is a perfect enzyme for a certain substrate

Are Enzymes reusable?

Yes or NO

Enzymes are…..

A.Nucleic Acids

B.Carbohydrates

C.Proteins

D.Lipids

Enzymes•3D shape •can be destroyed & denatured (change shape)

with extreme changes in pH & temperature •have active sites = places where substrate

(food & waste) molecules attach

Examples of Enzymes

Catalase breaks down hydrogen peroxide (waste produced in cells) into water and oxygen

2H2O2 ----> 2H2O + O2

Lactase breaks down lactose in milk

Protease breaks down proteins

Lipase breaks down lipids

How Enzymes Work?•Active sites on enzymes = places

where a specific substrate binds •Enzyme-substrate complexes

form (when substrates attach to active sites on the enzymes) to break apart or put together substances at a fast rate

•E+ S ES E + P

What are active sites?

Two Model of Enzymes

1.lock & key model → substrate & the enzyme fit together perfectly

2. induced-fit model →enzymes change shape slightly to accommodate the substrate

Lock & Key Model

Induced-Fit Model

Factors Affecting Enzyme Action

•Temperature – enzymes work best at certain temperatures

(– 37oC is best for human enzymes in the body)

•pH – enzymes work best at certain pH; basic, neutral, and/or acidic environments

ex.) Amylase in saliva at pH 7,

Pepsin in the stomach at pH 2-3,

Trypsin in the intestines at pH 9

37°

Temperature

temperature

reacti

on

rate

What’s happening here?!

humanenzymes

7

pH

pH

reacti

on

rate

20 1 3 4 5 6 8 9 10

stomachpepsin

intestinestrypsin

What’s happening here?!

11 12 13 14

•Substrate & enzyme concentrations – how fast reactions take place depends on how much of the substrate & enzyme is available.

•Coenzymes – helpers such as vitamins & minerals

Other Factors Affecting Enzyme Action