BIOLOGY
ENZYMES
1. In
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the Stomach, proteins are hydrolysed by the enzyme known as
trypsin, whose optimum pH is alkaline
lipase, whose optimum pH is acidic
pepsin, whose optimum pH is acidic
amylase, whose optimum pH is alkaline
maltase, whose optimum pH is acidic
I do not know
2. Choose the statement which is true about enzymes.
1. Enzymes do not require co-factors
2. Enzymes do not affect the amount of activation energy required by the
reaction
3. Enzymes increases the amount of activation energy required by the
reaction
4. Enzymes decreases the amount of activation energy required by the
reaction
5. None of the above statement is true
6. I do not know
3. The “Lock and Key” theory of enzyme action was proposed by
1. Fischer
2. Koshland
3. Chargaff
4. Watson and Crick
5. Rosalind Flanklin
6. I do not know
4. The optimum pH of the enzyme trypsin, which is found in the small
intestine is
1. acidic
2. above pH 7
3. neutral
4. either alkaline or acidic
5. below pH 6
6. I do not know
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5. Any molecule which acts irectly on an enzyme to lower its catalytic
activity is called
1. a co-enzyme
2. a co-factor
3. an inhibitor
4. a substrate
5. a product
6. I do not know
6. The effect of a reversible competitive inhibitor can be cancelled by
1. increasing the products concentration
2. increasing the substrate concentration
3. increasing the temperature
4. increasing the inhibitor concentration
5. decreasing the product concentration
6. I do not know
7. Which of the following is a co-enzyme?
1. Metal ion
2. Protein
3. Vitamin
4. Purine
5. Lipids
6. I d not know
8. In the Induced fit model of enzyme activity
1. the substrate changes its shape slightly after binding the enzyme
2. the enzyme active site changes its shape slightly after binding the
substrate
3. both enzyme and substrate changes their shapes after binding each
other
4. none of the enzyme and substrate changes their shapes after binding
each other
5. the enzyme and substrate have a perfect fit of each other.
6. I do not know
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9. The effect of competitive inhibitor on enzyme activity is such that it
1. reversibly increases enzymes activity
2. irreversibly stops enzyme activity
3. irreversibly increases enzyme activity
4. reversibly changes the shape of enzyme active site
5. reversibly stops enzyme activity
6. I do not know
10.
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A non-competitive or an allosteric inhibitor
changes the shape of the substrate
binds to the substrate
binds to the enzyme active site
competes with the substrate
does not bind to the enzyme active site
I do not know
11.
Choose the statement(s) which explain(s) why enzymes are good
biological catalysts
1. They are consumed in the reaction they catalyse
2. They are very specific and their effect is reversible
3. They lower the activation energy for the reaction they catalyse
4. They are rich in nucleotides
5. 2 and 3 above are correct
6. I do not know
12.
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Which of the following statement regarding enzymes is false?
Enzymes are proteins that function as catalyst
Enzymes are specific to their substances
Enzymes lower the activation energy for reaction
Enzyme activity cannot be inhibited
Enzyme may be used many times for a specific reaction
I do not know
13.
The temporal association between an enzyme and a substrate can
best be described as
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an enzyme-substrate complex
a covalent bond association
one in which the enzyme is changed permanently
a permanent mutual alteration of structure
complementary base pairing
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14.
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The active site of an enzyme
always remains rigid and does not change shape
is found on the surface of a globular protein
is the biggest part of protein molecule
contains amino acids with the same side chain
is also called an inhibitor site
I do not know
15.
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Which of the following bonds can be found in enzyme molecules?
Ionic bond
Peptide bond
Disulphide bond
Hydrogen bond
All the above are correct
I do not know
16.
Which of the following statement describes how the substrate fits
with the enzymes?
1. The lock and key hypothesis
2. The active site changes shape slightly after binding the substrate
3. The Induced fit hypothesis
4. The substrate fits exactly into the enzyme active site
5. all the above
6. I do not know
17.
is a biological catalyst that increases the rate of the reaction
without being changed.
1. A co-factor
2. A co-enzyme
3. An enzyme
4. An allosteric enzyme
5. An inorganic catalyst
6. I do not know
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18.
Enzymes increases the rate of chemical reactions by lowering the
activation energy.
1. True
2. When the optimum temperature is constant
3. False
4. Both 1 and 2
5. When temperature is above 40ºC
6. I do not know
19.
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An apoenzyme is a
protein portion of an enzyme
non protein group
complete biologically active conjugated enzyme
prosthetic group
an ester
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20.
The relationship between an enzyme and a reactant molecule can
best be described as follows
1. A temporary association
2. An association stabilized by an ionic bond
3. One in which the enzyme is changed permanently
4. a permanent mutual alteration of substrate
5. Non complementary binding
6. I do not know
21.
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The active site of an enzyme
does not change shape
is found at the centre of haemoglobin
site specific to the substrate
contains amino acids without side chains
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5. is inorganic in nature
6. I do not know
22.
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Which of the following statements regarding enzymes is false?
A given enzyme catalyse just one type of reaction
The activity of enzymes is impaired at high temperature
They do not alter the outcome of the reaction
While most enzymes are proteins, some are composed of RNA
The enzyme itself emerges unchanged from the reaction
I do not know
23.
Choose the statement which is true about enzymes.
1. Many enzymes do not require non protein groups to function
effectively
2. Enzymes do not change the amount of activation energy
3. Enzymes increases the amount of activation energy required
4. Enzymes decreases the amount of activation energy required
5. Enzymes are lipoproteins
6. I do not know
24.
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Which of the following statement is wrong about enzymes activity
Enzyme activity is directly dependent on substrate concentration
Enzyme activity is reduced by lowering temperature
One enzyme can catalyse more than one type of chemical reaction
The substrate binds the active site of the enzyme
If there were no enzymes in cells biochemical reactions would be very
slow
6. I do not know
25.
Change in the shape of an enzyme to the point were it loses its
function is called
1. deactivation
2. neutralization
3. denaturation
4. condensation
5. activation
6. I do not know
26.
The majority of enzymes work best at pH of
1. 1
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3
7
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14
I do not know
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