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Enzymes’

Enzyme Characteristic 1

Enzymes _________ __________ chemical reactions.

speed up

Enzyme Characteristic 2

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Tube A Tube B Tube CContains H2O2 & sand H2O2 & liver H2O2 & liverObservation

Tube A Tube B Tube C

Minute amounts of enzymes is needed to speed up the rate of reaction, without being chemically changed at

the end of the reaction.

Enzymes are required in minute amounts.

Maltase

Enzymes are required in minute amounts.

At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions.

Maltose

GluGlu

Maltase

At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions.

Maltose

GluGlu

Enzymes are required in minute amounts.

Maltase

At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions.

Maltose

GluGlu

Enzymes are required in minute amounts.

Maltase

At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions.

Maltose

GluGlu

Enzymes are required in minute amounts.

Maltase

Maltose

GluGlu

Hence, a minute amount of enzymes is enough to catalyse a chemical reaction.

Enzymes are required in minute amounts.Since enzymes remain chemically unchanged in the reactions they catalyse, the same enzyme can be used over and over again.

Recall

How do we name enzymes?

Based on the substrate they act on!

Enzymes are substrate specific.

Amylase Starch

Protease Proteins

Enzyme Characteristic 3

ACT ON

Lipids/ FatsLipase

Substrates

ACT ON

ACT ON

Enzyme Characteristic 3

An Enzyme

Active site

A depression on the surface of an enzyme molecule into which the substrate molecule(s) can fit

Enzyme Characteristic 3The specificity of an enzyme is due to its surface configuration or active site.

Demonstration

According to the “lock and key” hypothesis, the enzyme action depends on the active site.

Unsuitable substrate molecules will NOT FIT into the active site.Hence, the enzyme will not catalyse the reaction.

A

B

CD

CD

ONLY suitable substrate molecules will fit into the active site.The enzyme will then be able to catalyse the reaction.

Only Only certain substratecertain substrate can fit the can fit the active siteactive site of of an enzyme.an enzyme.

locklock keykey

• Each enzyme is a molecule with a specific shape.

• On part of its surface is the active site (the lock)—a section where its substrate molecule (the key) fits exactly.

• When the substrate molecule is in position in the active site, the enzyme alters the substrate, splitting it into its product molecules.

• The product molecules drift away from the enzyme molecule leaving its active site free to operate again.

What we learn today.

• Characteristics of Enzymes (Think: What are they?)

• “Lock and Key” Hypothesis (Describe)