Biological catalysts
Enzymess


Enzymes: proteins inside cells that act as a
catalyst.
Proteins = long amino acids chains that are folded into
a specific shape.
catalase
amylase
pepsin
trypsin

Catalyst : substance that speeds up the rate of a
chemical reaction but is not itself changed by the
reaction.
For example;
Hydrogen peroxide breaks down to water and oxygen
hydrogen peroxide
2H2O2 (l)
water + oxygen
2H2O (l) + O2 (g)

In our livers, catalase is the specific enzyme
that catalyses the breakdown of hydrogen
peroxide into water and oxygen.
Catalase
Inside the Cell
Step 1: Enzyme binds to substrate.
Substrate
Active site
Enzyme
Step 2: Substrate is changed into products.
Product
molecules
(combined into
something new or
broken down into
separate parts)
Enzyme
Step 3: Enzyme releases substrate,
ready to be re-used in another reaction.

Sketch & label this enzyme reaction into
your notes:
Active site:
place on the
enzyme where
the reaction
occurs
Substrate:
molecules upon
which enzymes
act
In enzyme catalyzed reactions,
enzymes
A. become a part of the new
products.
B. are destroyed by the reactants.
C. are not changed by the reaction.
D. are changed by the reaction.
Enzymes work like locks and keys

Lock and Key Hypothesis: the active site specifically
matches the shape of the substrate molecule.
enzyme
active site

Enzyme function:
http://www.youtube.com/watch?v=CZD5xsO
Kres&NR=1 (2:02)
Enzyme Reaction & Temperature


At low temperatures, enzyme-controlled
reactions go slowly.
At high temperatures, enzyme-controlled
reactions go quickly until optimum
temperature.
Enzyme Reaction & Temperature
 Optimum
temperature: The
temperature at which
the rate of reaction is
fastest.
Enzyme Reaction & Temperature
Once optimum temperature is surpassed, the heat
causes the enzyme to denature
 Denature: The enzyme changes shape and the active site
no longer matches the shape of the substrate molecule

Enzyme Reaction & pH

Enzymes prefer to work at an optimum pH.
Outside of its pH range, the enzyme is denatured.
Optimum pH
pepsin
amylase
Rate
Of
Reaction
1
2
3
4
5
6
7
pH
8
9
10
11
12

Concentration of enzymes - the more
enzymes, the faster the rate of reaction.

Concentration of substrates - the more
substrates, the faster the rate of reaction
What are some things that affect
enzyme activity?