1(a) Explain the consequence and
role of compartmentation of enzymes. (06 Marks)
(b) Write the open chain
structures for (a) D-gluconic acid and (b) D-glucoronic acid. (06 Marks)
(c) There are two possible chair
conformers of beta-D-glucopyranose. How many boat conformers are possible? (04
Marks)
(d) The specific rotation of
maltose in water is +138 degrees. What would be the concentration of a maltose
solution that had an optical rotation of +23 degrees if a polarimeter tube 10
cm long was used? (04 Marks)
2(a) Calculate the isoelectric
point of (a) arginine and (b) histidine. (06 Marks)
(b) What are the reasons for the
marked stability of an alpha helix? (06 Marks)
(c) What is meant by the
statement that a particular conformation of an amino acid residue lies in an
unfavourable region of the Ramachandran plot? (04 Marks)
(d) Theronine constitutes 1.8% by
weight of the amino acid content of insulin. Given that the molecular weight of
theronine is 119, what is the minimum molecular weight of Insulin? (04 marks)
3(a) Why is the triple helix of
collagen a better structure for providing tensile strength than the alpha
helix? (04 Marks)
(b) The identification of the
type and subtype of intermediate filament help in the diagnosis and
classification of cancer. Explain. (06 Marks)
(c) How many different molecules
of triacylglycerol can be made from glycerol and four different fatty acids?
(06 Marks)
(d) The pH of the gastric juice
is 1. The cells that produce gastric juice have an internal pH of 7. Calculate
the ΔG for transport of protons from these cells into the stomach at 37 degree
Celsius temperature. Given R = 8.3 J/mol.K. (04 Marks)
4(a) What feature of the amino
acid composition of histones enables them to interact strongly with DNA? (04
Marks)
(b) Why does messenger RNA have
the most heterogeneous base sequences of the major forms of RNA present in the
cytoplasm of a cell? (04 Marks)
(c) What is the basic difference
between the reaction catalyzed by (a) a mutase enzyme and that catalyzed by an
isomerase; (b) an oxidase, an oxygenase, and the reverse reaction of a
reductase? Give examples. (08 Marks)
(d) Give some examples of enzymes
that are smaller than their substrates. (04 Marks)
5(a) How does varying the
substrate concentration relative to the enzyme concentration affect the
validity of the steady-state assumption and the applicability of the
Michaelis-Menten expression? (06 Marks)
(b) Prove that the sum of the
control strengths of all enzymes in a linear sequence of reaction is 1. (06
marks)
(c) Write a brief note on the
role of ATP in bioenergetics. (04 Marks)
(d) Calculate the mean activity
coefficient in a solution of 0.25 mol L-1Na3PO4.
(04 Marks)
6(a) How is the concentration of
the glucose in the blood maintained (a) during rest after a carbohydrate–rich meal
and (b) during prolonged exercise? (04 marks)
(b) Termites exist almost
entirely on a diet of cellulose. How is the cellulose degraded by the termites
to carbohydrates, which can be used as an energy source. (06 Marks)
(c) If a protein inhibitor of
succinyl-CoA synthetase is applied to liver cells and germinating plant cells,
what effect would this have on energy production and the synthesis of
carbohydrate in both types of cell? (06 Marks)
(d) Calculate the number of
molecules of ATP that can be produced by substrate-level phosphorylation of ADP
from two molecules of acetyl-CoA in the (a) citric acid cycle and (b)
glyoxylate cycle. (04 Marks)
7(a) What effect would a
deficiency of carnitine palmitoytransferase in skeletal muscle have on the
ability of a person to perform prolonged exercise? (06 Marks)
(b) Why does feeding compounds
that act as methyl-group donors to patients with fatty liver alleviate the
condition? (04 Marks)
(c) How is it possible to distinguish
between the different cytochromes in the electron-transport chain? (06 Marks)
(d) Given that the internal pH of
a mitochondrion is 7.8, and assuming that a mitochondrion has a volume the same
as the sphere of diameter 1.4×10-6 m, calculate the number of
protons inside the mitochondrion. (04 Marks)
8(a) Glutamine from the diet and
from muscle during fasting can be converted into alanine in the intestine.
Which enzymes are involved in this conversion? (04 Marks)
(b) What feature of circular,
double-helical DNA is essential for it to function as a vector for DNA cloning?
(04 Marks)
(c) Decode the following RNA
sequence into the corresponding amino acid sequence:
CAU AUU ACU CAU GAA CGU GAA (06
Marks)
(d) What is the difference
between a repressor and a corepressor in relation to transcription? (06 Marks)
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