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CH 2012 TEST 1

LECTURER: MS C
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2
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4
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6
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8
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10
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False
The Michaelis constant is the rate of reaction that is half of Vmax
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True
Exergonic reactions are spontaneous
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True
All enzymes are protein in nature
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Class 2 enzymes catalyse
(a) Redox reactions
(b) transfer of groups within molecules to yield isomeric forms
(c) a transfer of a group, G (other than hydrogen), between a pair of substrates
(d) addition of groups to double bonds, or formation of double bonds by removal of groups
2
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(d) Modulators bind to the allosteric site on the enzyme via irreversible, covalent bonds
3
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(b) For any physical or chemical change, the total amount of energy in the universe remains
constant
(c) Energy may change form or it may be transported from one region to another, but it
cannot be created or destroyed
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______________ releases the most energy on hydrolysis
(a) Phosphenol pyruvate
(b) ATP
(c) Acetyl CoA

(d) Pyruvate
5
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Define any 10 of the following: (20marks)
(a) Transition state
It is the state at which a fraction of the reactant molecules has the energy necessary
to achieve a reactive condition
(b) enzyme kinetics
the field of biochemistry concerned with the quantitative measurement of the rates
of enzyme-catalyzed reactions and the systematic study of factors that affect these
rates
(c) enzyme inhibition
it is the slowing down or halting of enzyme catalysed reactions due to the
interference of molecular agents called inhibitors
(d) entropy
the amount of disorder in a system
(e) bioenergetics
a discipline within biochemistry that is dedicated to the study of energy flow within
living systems
(f) Enthalpy
The heat content of a reacting system
(g) free energy of activation
the energy required to raise the average energy of one mole of reactant (at a given


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Also called a second order reaction
(k) Glycolysis
The pathway by which glucose is broken down to pyruvate with release of ATP
(l) active site
the substrate binding site on an enzyme
2
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Active site takes up a relatively small part of the total volume of the enzyme

2
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Substrates are bound to active site by multiple weak interactions
4
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Water is usually excluded unless it’s a reactant
5
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List 3 covalent modifiers and the amino acids that accept these covalent modifiers (6 marks)
Phosphoryl group

Tyr, Ser, Thr, His

Adenylyl group

Tyr

Uridylyl group

Tyr

ADP-ribosyl group

Arg, Gln, Cys

Methyl group

Glu

4
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List 3 enzymes that catalyse irreversible reactions in glycolysis (3marks)
Hexokinase
Phosphofructokinase
Pyruvate kinase
6
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Illustrate the effect of substrate concentration on enzyme activity (6)

2
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Illustrate the effect of ph on enzyme activity (6)

4
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Illustrate the 3rd step of the first phase and the 3rd step of the second phase of glycolysis(6)


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if they use double arrows where there
should be a single arrow and single arrow where there should be double arrow, deduct 1
mark
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Illustrate 2 fates of pyruvate (6)

2 marks for each structure and 2 marks for the
enzyme

1 mark for each enzyme, 1
mark for acetaldehyde, 1 mark for ethanol and 2 marks for pyruvate

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