Download lab 3 enzymes F09

What are Enzymes?
Lab 3 – Enzymes
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Large protein molecules
They catalyze or speed up chemical reactions
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They aren’t changed in the reaction
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Chemical Reactions
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Cells constantly
rearrange molecules
by breaking existing
chemical bonds and
forming new ones.
Use enzymes
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Substrate
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Chemical Reactions
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Chemical reactions include:
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Enzymes catalyze reactions
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by decreasing the activation energy
Reactants, the starting materials
Products, the end materials
Enzymes are recycled
It takes energy to start a
chemical reaction
Catalyzed reactions go much
faster because the energy
needed to start the reaction –
or activation energy – is
lowered
Enzymes are catalysts that
speed up chemical reactions
in cells
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How Enzymes Work
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Temperature and pH alter
enzyme activity by changing the
shape of the protein
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Due to unfolding of the protein
chains
Can destroy enzyme activity
(denature the enzyme)
How Enzymes Work
The pH of the solution also affects enzyme
activity
Most enzymes work best at pH range of 6 - 8
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Except stomach enzymes that function at acidic
pH (around pH 2)
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Most enzymes work best at
body temperature
pH – another kind of measurement
Base
pH above 7
pH
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pH tells you the chemical properties of a
solution
measures the H+ concentration
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Neutral
pH=7
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The pH scale is logarithmic
a difference of 1 unit represents a 10-fold change in
concentration of hydrogen ions
Solution of pH 3 is 10 times more acidic than a
solution of pH 4
and 100 times more acidic than a solution of pH 5
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Acid
pH below 7
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Why is pH important?
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Chemical reactions within
cells are sensitive to pH
Small changes in pH can
alter enzyme activity
For example
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the pH of blood is 7.4
you would only live for a few
minutes if it were to fall to 7.0 or
rise to 7.8
Lab 3 = 3 experiments
Effect of temp on enzyme activity
1.
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Enzyme: rennin
Substrate: milk
Effect of pH on enzyme activity
2.
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Enzyme: catalase (potato)
Substrate: hydrogen peroxide
Learn about pH
3.
n
Measure pH of several solutions
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Expt 2: pH measurements
Expt 1: Rennin and temperature
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What is rennin?
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Role in digestion: curdles milk in the
stomach
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Enzyme that causes milk to coagulate
Produced by cells in the stomach lining
of mammals
Milk stays in the stomach longer and
can be digested more efficiently
Used in making cheese
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Use pH paper to measure the pH of
different solutions
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Acidic?
Basic?
Neutral?
Check out the pH of our tap water
Adding rennin causes milk protein
(casein) to curdle, yielding “curds and
whey”
Expt 3: Catalase and pH
Chemical Reactions
Catalase
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Common enzyme found in
nearly all organisms
Converts hydrogen peroxide, a
potentially harmful chemical, to
water and oxygen (gas)
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H 2O 2
H2 O + O2 (gas)
Substrate
H2 O2
Enzyme
Catalase
Products
H2 O + O2 (gas)
H2O2 is a byproduct of fat
metabolism, it must be
eliminated or it can kill the cell
Catalase and pH
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