think about… 4.1 metabolism 4.2 properties and actions of enzymes
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Think about… 4.1 Metabolism 4.2 Properties and actions of enzymes 4.3 Factors affecting the rate of enzymatic reactions 4.4 Applications of enzymes Recall ‘Think about…’ Summary concept map. Stonewashed jeans. Want old, worn-out jeans?. I can help you!. Stonewashed jeans. - PowerPoint PPT PresentationTRANSCRIPT
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Think about…
4.1 Metabolism
4.2 Properties and actions of enzymes
4.3 Factors affecting the rate of enzymatic reactions
4.4 Applications of enzymes
Recall ‘Think about…’
Summary concept map
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Want old, worn-out jeans?
I can help you!
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Wash jeans with stones.
Stones break some cellulose fibres & remove the blue dye.
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enzyme
Now we can use enzymes to break down the fibres more
quickly!
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1What are enzymes
enzyme
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2
enzyme
What are theimportance of enzymes to organisms
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What are the advantages of using enzymes in the making of stonewashed jeans
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enzyme
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• different chemical reactions take place in living cells
4.1 Metabolism
respiration
protein synthesis
lipid synthesis
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• different chemical reactions take place in living cells
4.1 Metabolism
sum of the chemical reactions that take place in an organism
= metabolism (新陳代謝 )
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Metabolism
Anabolism
(合成代謝 )
Catabolism
(分解代謝 )
4.1 Metabolism
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complex molecule
simple molecules
1 Catabolism
energy
4.1 Metabolism
• breaking-down reactions• release of energy
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• example: respiration
4.1 Metabolism
glucose
water
1 Catabolism
energy
carbon dioxide
+
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Metabolism
Anabolism
(合成代謝 )
Catabolism
(分解代謝 )
4.1 Metabolism
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simple molecules
complex molecule
energy
4.1 Metabolism
• building-up reactions• requires energy
2 Anabolism
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• example: condensation of glucose
4.1 Metabolism
glucose
2 Anabolism
energy
starch
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Anabolism
Metabolism
Catabolism
What are catabolism, anabolism and metabolism?
all breaking-down reactions in an organism
all building-up reactions in an organism
all chemical reactions in an organism
4.1 Metabolism
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4.2 Properties and actions of enzymes
What is the role of enzymes in
metabolism?
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4.2 Properties and actions of enzymes
reacting molecules
product (生成物 )
energy barrier (能障 )
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4.2 Properties and actions of enzymes
energy
reacting molecules
product (生成物 )
energy barrier (能障 )
Energy supplied to overcome the energy barrier
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reacting molecule
product
•analogy: pushing a rock up a hill 4.2 Properties and actions of enzymes
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the reaction does not start due to the presence of energy barrier
4.2 Properties and actions of enzymes
reacting molecule
productenergy barrier
•analogy: pushing a rock up a hill
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energy
when energy is supplied …
maximum energy
reaction starts
4.2 Properties and actions of enzymes
•analogy: pushing a rock up a hill
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How can the energy barrier be overcome in our body?
4.2 Properties and actions of enzymes
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By increasing the temperature?
• energy level raised
4.2 Properties and actions of enzymes
energy barrier is easier to overcome
smaller energy barrier
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By increasing the temperature?
4.2 Properties and actions of enzymes
smaller energy barrier
• energy level raised energy barrier is easier to overcome
Not possible because high temperature
kill the body cells!
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lower energy barrier
4.2 Properties and actions of enzymes
• rate of chemical reactions is speeded up by enzymes (酶 )
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energy
4.2 Properties and actions of enzymes
• rate of chemical reactions is speeded up by enzymes (酶 )
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4.1
Demonstration of the breaking-down action of enzymes
4.2 Properties and actions of enzymes
1 Prepare liver extract.
fresh pig liver
a Grind fresh liver with cold distilled water.
cold distilled water
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filter paper
liver extract
b Filter the ground tissue with filter paper.
4.2 Properties and actions of enzymes
4.1
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distilled water
liver extract
c Dilute the liver extract by 50% with cold distilled water.
4.2 Properties and actions of enzymes
4.1
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2 Set up 3 test tubes A to C. Observe for the release of gas and the gas given off with a glowing splint.
hydrogen peroxide
+ liver extractA
distilled water + liver extract
hydrogen peroxide + distilled waterB C
4.2 Properties and actions of enzymes
4.1
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Results and discussion
• A gas is released from tube A.
The gas is oxygen becauseit re-lights a glowing splint.• No oxygen is released from the control set-ups (tubes B and C).
4.2 Properties and actions of enzymes
4.1
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• Fresh liver tissues can break down hydrogen peroxide possibly due to the presence of catalase in the liver tissue.
• Catalase speeds up the breakdown of hydrogen peroxide.
Results and discussion
4.2 Properties and actions of enzymes
4.1
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enzyme
active site (活性部位 )
• each enzyme has an active site of a specific (專一的 ) shape
4.2 Properties and actions of enzymes
How do enzymes work?
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enzyme
substrate shapes fit together!
• active site can combine with substrate (受質 ) molecule(s)
4.2 Properties and actions of enzymes
How do enzymes work?
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• complex breaks down to give product(s)
• active site can combine with substrate (受質 ) molecule(s)
enzyme-substrate complex (酶受質複合物 )
4.2 Properties and actions of enzymes
How do enzymes work?
enzyme
substrate
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enzyme- substrate complex
• in catabolic reactions:
4.2 Properties and actions of enzymes
How do enzymes work?
substrate
enzyme
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enzyme unchanged and can be reused
enzyme- substrate complex
• in catabolic reactions:
products
4.2 Properties and actions of enzymes
How do enzymes work?
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• in anabolic reactions:
enzyme- substrate complex
4.2 Properties and actions of enzymes
How do enzymes work?
substrates
enzyme
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• in anabolic reactions:
enzyme- substrate complex
product
4.2 Properties and actions of enzymes
How do enzymes work?
enzyme unchanged and can be reused
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• act as catalysts (催化劑 ) in organisms
Properties of enzymes
1) Biological catalysts
speed up metabolic reactions
4.2 Properties and actions of enzymes
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• enzyme returns to its original form after reaction
Properties of enzymes
2) Reusable
after reaction
same!
before reaction
4.2 Properties and actions of enzymes
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Properties of enzymes
3) Required in small amount
large amount of products produced
4.2 Properties and actions of enzymes
reusablereusablereusable
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Properties of enzymes
4) Proteins
• enzymes are denatured (變性 ) at high temperatures and extreme pH
4.2 Properties and actions of enzymes
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Properties of enzymes
5) Specific action
4.2 Properties and actions of enzymes
different shape!
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Properties of enzymes
5) Specific action• each enzyme combines with a specific
substrateeach enzyme catalyses only one
type of reaction
4.2 Properties and actions of enzymes
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• can be explained by
Properties of enzymes
lock-and-keyhypothesis(鎖鑰假說 )
4.2 Properties and actions of enzymes
5) Specific action
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Lock-and-key hypothesis
• fit only a particular lock
4.2 Properties and actions of enzymes
specific shape
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• fit only a particular substrate
4.2 Properties and actions of enzymes
active sites of specific shape
Lock-and-key hypothesis
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Enzymes are biological catalysts
that chemical reactions
in organisms by lowering the
of reactions.
They are important in regulating
metabolism.
energy barrier
speed up
1
4.2 Properties and actions of enzymes
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An enzyme works when its
combines with substrate
(s) to form an
. The c
omplex then breaks down to give the
product(s). The enzyme is released in
its .
active site
original form
enzyme-substrate complex
2
4.2 Properties and actions of enzymes
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Enzyme actions are specific becaus
e their active sites have
. Enzyme combin
es only with substrate(s) that fits into
its active site. The specificity of enzy
me actions can be explained by the
.
specific shapes
3
lock-and-key hypothesis
4.2 Properties and actions of enzymes
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Five properties of enzymes:
i) They are biological
.
ii) They can be .
iii) They are required in
amount.
iv) They are .
v) Their actions are .
catalysts
specific
proteins
reused
small
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4.2 Properties and actions of enzymes
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Enzyme activity• reaction rate of an enzymatic reaction= the rate at which substrates are
used up or broken down= the rate of product formation
4.3 Factors affecting the rate of enzymatic reactions
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enzyme
4.3 Factors affecting the rate of enzymatic reactions
Enzyme activity• reaction rate of an enzymatic reaction= the rate at which substrates are
used up or broken down= the rate of product formation
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enzyme
4.3 Factors affecting the rate of enzymatic reactions
temperature pH
inhibitor
temperature
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Temperature
temperature( )℃
reaction rate
0 10 20 30 40 50 60
0˚C low kinetic energy
enzyme inactive
4.3 Factors affecting the rate of enzymatic reactions
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temperature( )℃
reaction rate
0 10 20 30 40 50 60
temperature rises
more kinetic energy
4.3 Factors affecting the rate of enzymatic reactions
Temperature
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have higher chance to form an enzyme-substrate complex
molecules vibrate more rapidly
collide more frequently
4.3 Factors affecting the rate of enzymatic reactions
more kinetic energy
Temperature
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4.3 Factors affecting the rate of enzymatic reactions
Temperature
temperature( )℃
reaction rate
0 10 20 30 40 50 60
temperature rises
more kinetic energy
reaction rate increases
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Temperature
temperature( )℃
reaction rate
0 10 20 30 40 50 60
optimum temperature rate of enzymatic reaction reaches maximum
maximum rate
4.3 Factors affecting the rate of enzymatic reactions
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Temperature
temperature( )℃
reaction rate
0 10 20 30 40 50 60
temperature higher than optimum temperature enzyme denatured
reaction rate decreases
4.3 Factors affecting the rate of enzymatic reactions
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Enzymes are killed by heating so the rate of enzymatic reaction decreases.
4.3 Factors affecting the rate of enzymatic reactions
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Enzymes are NOT living things. They cannot be killed. They are denatured (their shapes are changed) at very high temperatures.
4.3 Factors affecting the rate of enzymatic reactions
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4.2
Investigation of the effect of temperature on enzyme activity
4.3 Factors affecting the rate of enzymatic reactions
1 Add amylase solution to test tubes A to F. Add starch solution to test tubes 1 to 6.
2 Leave the different pairs of test tubes in water baths at different temperatures for 10 minutes.
Simulation
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4.2
ice
A 1
0˚C
B 2
20˚C
C 3
40˚C
D 4
60˚C
E 5
80˚C
F 6
100˚C
starch solution
amylase solution
4.3 Factors affecting the rate of enzymatic reactions
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4.2
3 Pour the amylase solution into starch solution. Put the tube of mixture back to its beaker. Record the time as zero.
A
1
amylase solution
starch solution
4.3 Factors affecting the rate of enzymatic reactions
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4.24 At 2-minute intervals, transfer a drop of each mixture to an iodine drop. Record the
time it takes for the blue-black colour to disappear.
amylase and starch mixture
iodine drops
spot plate
4.3 Factors affecting the rate of enzymatic reactions
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4.2
Results and discussion
• The time it takes for the blue-black colour to disappear is the shortest at 60˚C.
4.3 Factors affecting the rate of enzymatic reactions
• The starch does not disappear at 0˚C, 80˚C and 100˚C.
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4.2
• At low temperature, the enzymatic reactionrate is low because amylase is inactive.
• Its activity increases with temperature until it reaches a maximum (around 60˚C).
Results and discussion
4.3 Factors affecting the rate of enzymatic reactions
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4.2
• The enzyme activity is the highest at 60˚C.
• Above the optimum temperature, the enzyme activity decreases and the reaction rate decreases until the enzyme becomes denatured and can no longer work.
Results and discussion
4.3 Factors affecting the rate of enzymatic reactions
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enzyme
4.3 Factors affecting the rate of enzymatic reactions
temperature pH
inhibitor
pH
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reaction rate
2 4 6 8 10 12 14pepsin
many enzymes in mammals (e.g.
salivary amylase)
pancreatic lipase
pH4.3 Factors affecting the rate of enzymatic reactions
pH
752 4 6 8 10 12 14
reaction rate
each enzyme works in a narrow range of pH
pH
pH4.3 Factors affecting the rate of enzymatic reactions
762 4 6 8 10 12 14
reaction rate
each enzyme have their own optimum pH
unsuitable pH causes denaturation
optimum pH for most enzymes: pH 5 – pH 9
pH4.3 Factors affecting the rate of enzymatic reactions
pH
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4.3
Investigation of the effect of pH on enzyme activity
4.3 Factors affecting the rate of enzymatic reactions
1 Add Benedict’s solution to test tubes 1 to 6.
Benedict’s solution
Simulation
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2 Add sucrose solution to another 6 test tubes A to F. Then add citrate-phosphate buffer solution at different pH values to the tubes as shown.
Tube A B C D E F
pH of buffer solution
3.2 4.0 5.2 6.0 7.0 8.0
4.3
4.3 Factors affecting the rate of enzymatic reactions
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3 Add invertase solution to test tubes A to F. Leave at room temperature for 5 minutes.
4.3
sucrose solution + citrate-phosphate buffer + invertase
4.3 Factors affecting the rate of enzymatic reactions
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4 Pour the Benedict’s solution in test tubes 1 to 6 into test tubes A to F respectively. Shake the tubes gently. Put the test tubes into a boiling water bath for 10 minutes.
4.3
boiling water
4.3 Factors affecting the rate of enzymatic reactions
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5 Allow the tubes to stand for 15 minutes.Measure the depth of any brick-red precipitate settled in the test tubes.
4.3
4.3 Factors affecting the rate of enzymatic reactions
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4.3
Results and discussion• Precipitate is formed in tubes A, B, C and
D. The largest amount of precipitate is settled in tube C. No precipitate is formed in tubes E and F.
• The results show that invertase works in an acidic medium. It has an optimum pH value around pH 5.2.
4.3 Factors affecting the rate of enzymatic reactions
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enzyme
4.3 Factors affecting the rate of enzymatic reactions
temperature pH
inhibitor inhibitor
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Inhibitors4.3 Factors affecting the rate of enzymatic reactions
• inhibitors (抑制劑 ) are chemicals that slow down or stop the activities of enzymes
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Competitiveinhibitors
(競爭性抑制劑 )
Non-competitiveinhibitors
(非競爭性抑制劑 )
Inhibitors
4.3 Factors affecting the rate of enzymatic reactions
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1 Competitive inhibitors
substratecompetitive inhibitor
similar shape!
4.3 Factors affecting the rate of enzymatic reactions
Animation
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• compete with substrates for active sites
active site
enzyme
4.3 Factors affecting the rate of enzymatic reactions
substrateinhibitor
1 Competitive inhibitors
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inhibitor prevents binding of substratechance to form enzyme-substrate complex lowered
4.3 Factors affecting the rate of enzymatic reactions
enzyme
reaction rate decreases
1 Competitive inhibitors
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substrate can bind when inhibitor leaves
reversible binding
4.3 Factors affecting the rate of enzymatic reactions
enzyme
1 Competitive inhibitors
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reaction rate increases
more substrates, greater chance of binding
4.3 Factors affecting the rate of enzymatic reactions
1 Competitive inhibitors
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Inhibitors
Competitiveinhibitors
(競爭性抑制劑 )
Non-competitiveinhibitors
(非競爭性抑制劑 )
4.3 Factors affecting the rate of enzymatic reactions
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substratenon-competitive inhibitor
shape not similar
2 Non-competitive inhibitors4.3 Factors affecting the rate of enzymatic reactions
• do not compete for active sites
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2 Non-competitive inhibitors
active site changes shape
4.3 Factors affecting the rate of enzymatic reactions
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2 Non-competitive inhibitors4.3 Factors affecting the rate of enzymatic reactions
not fit together!
reaction rate decreases
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• increasing substrate concentration cannot increase reaction rate
2 Non-competitive inhibitors4.3 Factors affecting the rate of enzymatic reactions
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• examples:
2 Non-competitive inhibitors4.3 Factors affecting the rate of enzymatic reactions
cyanideheavy metals
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4.4
Investigation of the effect of inhibitors on enzyme activity
4.3 Factors affecting the rate of enzymatic reactions
Acopper(II) suphate +sucrose
1 Add Benedict’s solution to test tubes 1 to 3.
2 Prepare test tubes A to C.Bsilver nitrate + sucrose
Cdistilled water + sucrose
Video
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4.4
3 Add 10 drops of invertase solution to test tubes A to C. Leave the tubes at room temperature for 5 minutes.
4.3 Factors affecting the rate of enzymatic reactions
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4.4
4 Pour Benedict’s solution in test tubes 1 to 3 into test tubes A to C respectively. Shake the tubes gently. Put the test tubes into a boiling water bath for 10 minutes.
boiling water
4.3 Factors affecting the rate of enzymatic reactions
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4.4
5 Allow the tubes stand for 15 minutes.Measure the depth of any brick-red precipitate settled in the test tubes.
4.3 Factors affecting the rate of enzymatic reactions
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4.4
Results and discussion
• Precipitate is formed in control set-up (tube C). No precipitate is formed in tubes A and B.
• The results show that copper(II) ion and silver ion are inhibitors of enzyme invertase. Their presence slows down the action of invertase on sucrose.
4.3 Factors affecting the rate of enzymatic reactions
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1 Effect of temperature on enzymes:
Temperature Enzymes
Low temperature
Work best
High temperature
Inactive
Optimum temperature
Denatured
4.3 Factors affecting the rate of enzymatic reactions
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2 Effect of pH on enzymes:
pH Enzymes
Work best
Extreme pH
Optimum pH
Denatured
4.3 Factors affecting the rate of enzymatic reactions
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3 Difference between competitive and non-competitive inhibitors:
Competitive Non-
competitive
Shape of molecule
4.3 Factors affecting the rate of enzymatic reactions
Are they similar to substrate?
Similar Not similar
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Competitive Non-
competitive
Action
4.3 Factors affecting the rate of enzymatic reactions
What is their mode of action?
Change the shape of enzyme
Compete for active
site
3 Difference between competitive and non-competitive inhibitors:
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Competitive Non-
competitive
Increased substrate concentration
4.3 Factors affecting the rate of enzymatic reactions
Will the rate of enzymatic reaction
increase?Yes No
3 Difference between competitive and non-competitive inhibitors:
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4.4 Applications of enzymes
• used to produce useful commercial products
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• example:
lipases and proteasesto remove stains
containing lipids and proteins
biological washing powder
4.4 Applications of enzymes
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• example:
papainto soften meat
meat tenderizer
a protease extracted from papaya
4.4 Applications of enzymes
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• example:
proteasesto coagulate (凝固 )
milk in cheese production
cheese
extracted from young cows’ stomach
4.4 Applications of enzymes
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• example:
to modify starch to keep the bread soft
bread
4.4 Applications of enzymes
enzymes
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• example:
to break down plant cell walls so that the juice looks less cloudy
fruit juice
4.4 Applications of enzymes
enzymes
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• example:
to remove hairs from hides (牛皮 )
to soften leatherleather
4.4 Applications of enzymes
enzymes
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What are the advantages of using enzymes?
4.4 Applications of enzymes
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• reduce the production of unwanted products
Specific in action1
4.4 Applications of enzymes
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• lower the cost of production
Efficient in small amount2
4.4 Applications of enzymes
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• extreme and expensive conditions not required
Work at moderate conditions3
4.4 Applications of enzymes
e.g. high temperaturehigh pressure
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4.5
Investigation of protease activities in different fruit juices
4.4 Applications of enzymes
1 Heat the end of a cork borer in a Bunsen flame and allow it to cool.
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4.5
4.4 Applications of enzymes
cork borer
wellmilk agar plate
2 Gently press the borer down into the milk-agar plate to make five wells. Replace the lid quickly.
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4.53 Use a clean dropper to fill the wells A–D with pineapple juice, kiwi fruit juice, papaya
juice and guava juice. Fill well E with distilled water.
distilled water
different fruit juices
4.4 Applications of enzymes
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4.5
4 Replace the lid. Incubate the plate at 35˚C for one hour.
incubator
4.4 Applications of enzymes
122
4.5
5 Measure the diameter of the clear zones around the wells by placing the plate on graph paper and examining against light.
4.4 Applications of enzymes
123
4.5
Results and discussion
• Clear zones are observed around the wells containing fruit juices and their diameters are different.
• The well containing distilled water is a control. No clear zone is formed around it.
4.4 Applications of enzymes
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4.5
Results and discussion• The results show that pineapple, kiwi fruit, papaya and guava contain
proteases that can break down proteins, but the activities of the proteases differ from one another.
4.4 Applications of enzymes
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4.6
Design an investigation of the effectiveness of different biological washing powder
Which brand of biological washing powder is the most effective in removing food stains? Design an investigation to find this out.
4.4 Applications of enzymes
Video
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tenderizers
Enzyme are widely used in industry
to produce useful products e.g.
biological and
meat . They are also
important in food industries,
breweries and leather industries.
washing powder
4.4 Applications of enzymes
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enzyme
What are enzymes?1Enzymes are biological catalysts. They speed up metabolic reactions in organisms.
128
enzyme
What is the importance2Without enzymes, metabolic reactions will not proceed under the relatively low temperatures.
of enzymes to organisms?
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enzyme
What is the advantage of 3
This can shorten the time of jean production.
using enzymes in the making of stonewashed jeans?
130
lower the
Enzymes
metabolic reactions
energy barriertherefore speed up
include
anabolic reactions
catabolic reactions
131
Enzymes have an
active site
specificity
lock-and-key hypothesis
shows
can be explained by
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Enzymes activities affected by
temperature pH inhibitors
inactivation of enzymes
denaturation of enzymes
too low causes
too high causes
extreme values cause
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inhibitors
competitive non-competitive
may be