Transcript Document 250063

National 5 Cell Biology
Enzymes
We are learning to:
•
•
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Describe the properties of an enzyme
Explain the importance of enzymes
Describe an enzyme reaction
Explain the specificity of enzymes for their
substrate
What I'm looking for:
• Mind map showing the properties of enzymes
• Labelled diagram showing the stages of an
enzyme reaction
• 2 examples of degradation enzymes
• 1 example of a synthesis enzyme
What are enzymes made of?
Enzymes are protein molecules. They are made up of
amino acids. Most enzymes contain between 100 and
1,000 amino acids.
These amino acids are joined together in a long chain,
which is folded to produce a unique 3D structure.
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Why do enzymes speed up reactions?
Enzymes speed up reactions by lowering the activation
energy (Ea) of a reaction. The activation energy is the
energy needed to start a reaction.
Different reactions have different activation energies.
energy (kJ)
Ea without enzyme
Ea with enzyme
reaction (time)
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Fussy enzymes?
Why are enzymes so specific in their reactions?
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Why are enzymes so specific?
Enzymes are very specific about which reactions they
catalyse. Only molecules with exactly the right shape will
bind to the enzyme and react. These are the substrate
molecules.
The part of the enzyme to
which the reactant binds is
called the active site.
This is a very specific shape
and the most important part
of the enzyme.
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The lock and key model
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What happens at the active site?
In the same way that a key fits into a lock, so a substrate
is thought to fit into an enzyme’s active site. The enzyme
is the lock, and the reactant is the key.
↔
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enzyme
+
substrate
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↔
↔
enzyme-reactant
complex
+
↔
enzyme
+
products
© Boardworks Ltd 2007
SUBSTRATE
PRODUCT
ACTIVE
SITE
ENZYME
ENZYME- SUBSTRATE
COMPLEX
I can:
•
•
•
•
Describe the properties of an enzyme
Explain the importance of enzymes
Describe an enzyme reaction
Explain the specificity of enzymes for their
substrate
Experiment One
A
5ml
starch
+
5ml
B
amylase
5ml
starch
+
5ml
water
Shake the boiling tubes to mix.
Take a sample and test for starch every 3mins.
After 15mins test both tubes for sugar.
Results
Apparatus
Tube A
Tube B
Dimple Tray A
Dimple Tray B
Final Colour
Substance
Present
Conclusion
________
Substrate
___________
End Products
Experiment Two
1
2
3
4
5
Hydrogen
peroxide
Hydrogen
peroxide
Hydrogen
peroxide
Hydrogen
peroxide
Hydrogen
peroxide
+
+
+
+
+
raw
potato
raw carrot fresh
liver
raw apple
boiled
liver
1
2
3
Bubbles
of
oxygen
4
5
Hydrogen
peroxide
Hydrogen
peroxide
Hydrogen
peroxide
Hydrogen
peroxide
Hydrogen
peroxide
+
+
+
+
+
raw
potato
raw carrot fresh
liver
Raw apple
boiled
liver
Table of Results
Type of Tissue Height of Froth (mm)
Potato
Carrot
Liver
Apple
Control
Conclusion
________
Substrate

________ + _______
End Products
Experiment Three
A
B
C
D
4 drops of glucose-1phosphate in A-D.
Add a drop of potato
extract to each.
Immediately add a drop of iodine solution to A.
Test B = 4mins, C = 8mins, D = 12mins.
REMEMBER IODINE TURNS STARCH BLUE/BLACK.
Results
Time
(mins)
0
Colour of Iodine
A
4
B
8
C
12
D
Conclusion
G
G
G
G
G
G
G
G
G
G
G
Glucose-1-phosphate
is a reactive form of
glucose
Small part of long
starch molecule
Phosphoryase – builds up starch
G