Class:
4
4.1
(
Name:
)
Date:
Enzymes and metabolism
Metabolism
(Book 1A, p. 4-3)
(1) _______________ (新陳代謝) is the sum of chemical reactions that take place in an
organism. It includes (2) _______________ (分解代謝) and (3) _______________ (合成代謝).
Catabolism
Anabolism
energy
complex molecule
energy
simple molecules
simple molecules
complex molecule
The (4) ______________ (breaking-down /
The (6) ______________ (breaking-down /
building-up) reactions in an organism.
building-up) reactions in an organism.
Energy is (5) _______________ (released /
Energy is (7) _______________ (released /
required).
required).
4.2
The role of enzymes in metabolism
(Book 1A, p. 4-4)
For every reaction, a certain amount of energy must be supplied to the reactants before the
reaction can occur. This is called the (1) _______________ _______________ (活化能).
In our body, (2) _______________ (酶) are present which function as biological catalysts (催化劑).
They help (3) _______________ (raise / lower) the activation energy so that chemical reactions
can take place at body temperature at a faster rate.
energy level
activation energy
(without enzyme)
activation energy
(with enzyme)
reactants
products
progress of reaction
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Go to
Practical 4.1
Demonstration of the breaking-down action of enzymes
(Book 1A, p. 4-5; Practical Workbook for SBA 1A, p. 4-1)
Practical 4.2
Demonstration of the building-up action of enzymes
(Book 1A, p. 4-6; Practical Workbook for SBA 1A, p. 4-4)
4.3
A
Actions and properties of enzymes
How do enzymes work?
(Book 1A, p. 4-7)
(Book 1A, p. 4-7)
On each enzyme molecule, there is an (1) _______________ _______________ (活性部位). An
enzyme molecule only binds to (2) _______________ (受質) molecules that fit the shape of its
active site.
A metabolic reaction begins when the substrate molecule(s) bind to the active site of an
enzyme to form an (3) _______________-_______________ _______________ (酶受質複合物).
Its formation (4) _______________ (raises / lowers) the activation energy of the reaction.
The substrate(s) are converted into product(s). The enzyme molecule is released in its
(5) _______________ form.
Catabolic reactions
shapes fit
together
substrate
enzyme-substrate
complex
products
enzyme
unchanged
enzyme
active site
enzyme can be reused
Anabolic reactions
enzyme-substrate
complex
substrates
shapes fit
together
enzyme
product
enzyme
unchanged
active site
enzyme can be reused
▲ Enzyme action in metabolic reactions
The specificity of enzyme actions can be explained by the (6) ___________- _____________ _____________ _______________ (鎖鑰假說).
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B
What are the properties of enzymes?
Property
(Book 1A, p. 4-8)
Description
Enzymes are biological
Enzymes speed up metabolic reactions by lowering the
(7) _______________.
(8) _______________ energy of the reactions.
The actions of enzymes are
An enzyme only acts on substrates that fit into its
(9) _______________.
(10) _______________ _______________.
Enzymes are
The structures and hence the activity of enzymes are easily
(11) _______________.
affected by temperature and pH. Most enzymes are
(12) _______________ (變性) at high temperatures.
Enzymes are
Enzymes remain unchanged after reactions. They can bind to
(13) _______________.
other substrate molecules after the reaction is complete.
Enzymes are needed in relatively
Since enzymes can be (15) _______________, they are
(14) _______________ amounts.
usually needed in small amounts only.
4.4
Factors affecting the rate of enzymatic reactions
(Book 1A, p. 4-10)
A
Temperature
(Book 1A, p. 4-10)
reaction rate
maximum rate
enzymes are
denatured
enzymes are
inactive
temperature (℃)
10
20
30
40
50
60
optimum temperature
for this enzyme
▲ Effect of temperature on the rate of an enzymatic reaction
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At low temperatures, enzymes are (1) ______________ (不活躍). The enzyme and substrate
molecules move slowly and the chance for them to (2) _______________ with each other is low.
Therefore, the reaction rate is (3) _______________.
As the temperature rises, both enzyme and substrate molecules move around more rapidly and
collide with each other more (4) ______________. This increases the chance of forming
(5) _____________-_____________ ______________. As a result, the rate of the enzymatic
reaction (6) _______________.
The rate of enzymatic reaction will eventually reach a maximum at (7) _______________
_______________ (最適溫度).
High temperatures may cause (8) _______________ change (i.e. a change in shape) in the
active site of the enzyme molecule. The enzyme is said to be (9) _______________. The
substrate molecule can no longer fit into the active site of the enzyme. As a result, the rate of
the enzymatic reaction (10) _______________.
B
pH
(Book 1A, p. 4-12)
Most enzymes work in a (11) _______________ (wide / narrow) range of pH. They work best
at their (12) _______________ pH.
Similar to the effect of high temperatures, an unsuitable pH will cause (13) _______________
of the enzyme. Therefore the rate of the enzymatic reaction (14) _______________.
many enzymes in mammals
(e.g. salivary amylase)
pancreatic lipase
reaction rate
pepsin
2
4
optimum
pH
6
8
10
12
14
pH
optimum optimum
pH
pH
▲ Different enzymes have their own optimum pH
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C
Inhibitors
(Book 1A, p. 4-15)
(15) _______________ (抑制劑) are chemicals that can decrease the rate of enzymatic
reactions. Cyanides and (16) _______________ _______________ (重金屬) such as mercury
ions, lead(II) ions and copper(II) ions are examples of inhibitors.
Go to
Practical 4.3
Investigation of the effect of temperature on enzyme activity
(Book 1A, p. 4-11; Practical Workbook for SBA 1A, p. 4-8)
Practical 4.4
Design an investigation of the effect of pH on enzyme activity
(Book 1A, p. 4-13; Practical Workbook for SBA 1A, p. 4-12)
Practical 4.5
Investigation of the effect of inhibitors on enzyme activity
(Book 1A, p. 4-15; Practical Workbook for SBA 1A, p. 4-17)
4.5
Applications of enzymes
(Book 1A, p. 4-18)
Enzymes produced by organisms also work well outside the organisms. They are extracted and
used to produce various commercial products.
Examples of products and the enzymes used:
Enzyme used
Product
I
Biological washing powders
a
Protease
II
Stonewashed jeans (石磨藍牛仔褲)
b
Lipase
III Contact lens cleaners
c
Cellulase
IV Meat tenderizers
d
Papain (木瓜酶)
V
e
Pectinase (果膠酶)
Cheese
VI Fruit juices
I: (1) _______ & (2) _______
II: (3) _______
III: (4) ______
IV: (5) _______
V: (6) _______
VI: (7) ______
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Advantages and limitations of using enzymes in the production of commercial products:
Advantage
Limitation
Enzymes can speed up chemical
Enzymes are sensitive to
reactions. This (8) _______________ the
(15) _______________ and
production time and allows the
(16) ________ changes. High
(9) _______________ production of
temperatures and unsuitable pH can cause
products.
(17) _______________ of enzymes.
Enzymes are (10) _______________ in
Enzymes are easily affected by
action. This can reduce the production
(18) _______________. All containers
of (11) _______________ products.
that are used in the production processes
Enzymes are (12) _______________ and
have to be (19) _______________. This
are needed in small amounts only. This
prevents the containers from
lowers the (13) ______________ of
(20) _______________ with inhibitors.
production.
Many enzymes work at
(14) _______________ conditions. Using
enzymes in the production processes does
not require extreme conditions.
Go to
Practical 4.6
Investigation of the effectiveness of different biological washing powders
(Book 1A, p. 4-20; Practical Workbook for SBA 1A, p. 4-20)
Practical 4.7
Design an investigation of protease activities in different fruit juices
(Book 1A, p. 4-21; Practical Workbook for SBA 1A, p. 4-24)
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Answers
Ch 4
Enzymes and metabolism
4.1
1
Metabolism
2
catabolism
3
anabolism
6
building-up
7
required
activation energy
2
1
active site
5
4
enzymes
3
lower
2
substrate
3
enzyme-substrate complex
original
6
lock-and-key hypothesis
9
specific
10
active site
14
small
15
reused
1
inactive
2
collide
5
enzyme-substrate complexes
8
conformational
9
13
denaturation
1
breaking-down
5
released
4
lowers
4.2
1
4.3
7
catalysts
8
activation
13
reusable
11
proteins
12
denatured
3
low
4
frequently
6
increases
7
optimum temperature
denatured
10
decreases
11
narrow
14
decreases
15
Inhibitors
16
heavy metals
a
2
b
3
c
4
6
a
7
e
8
shortens
11
unwanted
12
reusable
13
16
pH
17
denaturation
18
4.4
12
optimum
a
5
d
9
mass
10
specific
cost
14
moderate
15
temperature
inhibitors
19
clean
20
contaminating
4.5
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