Enzymes are ORGANIC CATALYSTS!

Enzymes are proteins (made up of amino acids)

Enzymes function by lowering the activation energy of reactions.

Enzymes can act rapidly and can cause chemicals to act 107 times faster than without the enzyme present.

There are over 2000 known enzymes, each of which is involved with one specific chemical reaction.

All chemical reactions require activation energy to break chemical bonds and begin the reaction.

Enzymes lower the barriers that normally prevent chemical reactions from occurring (or slow them down) by decreasing the required activation energy. Thus, in the presence of enzymes, reactions proceed and/or proceed at a faster rate.

Generally speaking, these are the terms to be familiar with

Substrate Enzyme Active Site Products

Specific Binding SiteAn enzyme has a

for a specific substrate to bind

Enzymes are substrate specific.

i.e. The enzyme peptidase (which breaks bonds in proteins) will not work on starch (which is broken down by amylase in the mouth)

When the substrate and enzyme bind it forms a

Lock and Key Model

Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).

The active site of the unbound enzyme is not the exact complement of the shape of the substrate.

However, the enzyme does bind to the substrate.

After binding of the enzyme to the substrate is initiated, a conformational change in the shape of the active site which results in a new shape of the active site that is complementary to the shape of the substrate.

Induced Fit Model

Here’s an example of an enzyme that bonds with the sucrose (SUBSTRATE)

Once water is added and the bond breaks in the sucrose molecule and a glucose and fructose molecule are released (PRODUCTS)

1 Maltose + Enzyme 2 Glucose + Enzyme

Reactant Product

Maltase

Competitive Non-competitive

pH

Factors that affect the reaction

Temperature

• Increases in temperature will speed up the rate of the reaction

• When heated too much, enzymes will become denatured (lose their shape)

• Changes in pH will also denature the enzyme by changing the shape of the enzyme

• Enzymes are also adapted to operate at a specific pH or pH range

Examples of enzymes:

• Ligase

• Transferase

• Lactase

• Maltase

• Carbonic anhydrase

• Peptidase

•Salivary amylase

• Isomerase

• Cellulase

• Pectinase

• Catalase

• Peroxidase

• Sucrase

• Oxidase

You may have heard of people who are lactose intolerant, or you may suffer from this problem yourself. The problem arises because the sugar in milk – lactose – does not get broken down into its glucose components. Therefore, it cannot be digested.

The intestinal cells of lactose-intolerant people do not produce lactase, the enzyme needed to break down lactose. This problem shows how the lack of just one enzyme in the human body can lead to problems.

A person who is lactose intolerant can swallow a drop of lactase prior to drinking milk and the problem is solved. Many enzyme deficiencies are not so easy to fix!

Other world applications:

• Some liver diseases = result from lack of enzymes

• Tay-Sachs disease = lack an enzyme necessary for breaking down certain fatty substances in brain and nerve cells

• Fabry Disease = A chemical in the body which would normally be broken down builds up and causes damage, mainly to the heart, kidneys and brain

•Lysosomal Storage Disorder (i.e Gaucher Disease: an enzyme is missing in cells in the bones, bone marrow, liver and spleen.  There is an accumulation of waste in these tissues in the body and they become enlarged)

•Glycogen storage disease (i.e. Pompe disease) = missing enzyme that is needed to break down glycogen, a stored form of sugar used for energy