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Biochemistry Question Paper

Biochemistry

Course:Bachelor Of Pharmacy

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2008/2009
SECOND SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR
OF PHARMACY

HMB 110:
BIOCHEMISTRY

DATE: Wednesday, 9th September, 2009
TIME: 11.00 a.m. – 1.00 p.m.

SECTION A: Answer any 2 questions (20 marks each)
Q.1
a)
Salicylate inhibits the catalytic action of glutamate dehydrogenase.

From the following data:-
i)
Determine the type of inhibition by graphical analysis of the data.
ii)
Calculate the Km for the substrate
iii)
The Ki, the dissociation constant for the enzyme – inhibitor
complex.
Assume that the salicylate concentration is held constant at 20mM.
Either or both of the equations below may be necessary.
? [ ]
V max
Km1 = Km + 1
1

?
?
?
V
1 =

?
Ki ?
max
? [ ]
+ 1
1
?
?
?
?
Ki ?
Substance
Concentration
Product
per
minute,
mg
MM
without
salicylate

with
salicylate
1.5
0.21
0.08
2.0
0.25
0.10
3.0
0.28
0.12
4.0
0.33
0.13
8.0
0.44
0.16
16.0
0.40
0.18

(12 marks)

b)
Considering a single substrate enzyme – catalyzed reaction, derive an
V max [S]
expression V =

Km +[S]
What assumptions have you made to arrive at the equation. (6 marks)

c)
Calculate the relationship of Km to [S] when an enzyme catalyzed
reaction is operating at 80% of the maximum velocity.
(2 marks)
Page 1 of 2

Q.2
a)
How does the concept proposed by Arrhenius Bronsted – Lowry & Lewis
explain
acids
and
bases?
(10
marks)
b)
The dissociation constant of two weak acids formic and acetic acid are
21.4 x 10-5 and 1.81 x 10-5 respectively.
Derive a relevant expression and use it to calculate the relative strength of
these acids.

(10 marks)

Q.3
a)
i)
Given that Lactic acid (HA) is a weak and dissociates into H+ and
A-, derive the Henderson-Hasselbalch equation.
(6 marks)

ii)
Calculate the pKa of lactic acid, given that when the concentration
of lactic acid is 0.010M and the concentration of lactate is 0.087
M, the pH is 4.80.

(2 marks)

iii)
Calculate the ratio of the concentrations of acetate and acetic acid
required in a buffer system of pH 5.30. (The pKa of acetic acid is
4.76).
(2
marks)

b)
Describe
and
explain
the Bicarbonate buffer system that exists between
the blood in capillaries and the lung air spaces.

(10 marks)

SECTION B:
Answer ALL questions: (10 marks each)
Q.4 Indicate
the
structures and functions of the following biomolecules.

i)
Vitamin A
ii)
cAMP
iii)
Cortisol
iv)
Cysteine
v)
D-glucose
(10 marks)

Q.5
Describe co-operatively in the binding of haemoglobin for oxygen as model for
allosteric
control
of
enzymes.
(10
marks)

Q.6
a)
Distinguish between hydrophobic interactions and van der waals forces.

(4 marks)

b)
Write briefly on three important properties of water that makes it an ideal
medium
for
living
organisms.
(6
marks)
Page 2 of 2

Biochemistry Question Paper

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