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Biochemistry Iii Question Paper

Biochemistry Iii

Course:Pharmacy

Institution: Kenyatta University question papers

Exam Year:2010

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF PHARMACY

HMB 130: BIOCHEMISTRY III
DATE: Monday, 26th July, 2010 TIME: 8.00 a.m. – 10.00 a.m.

INSTRUCTIONS:

Answer ALL questions.
1. a) Describe:
i) the roles of glutamine synthetase and glutaminase in the
metabolism of amino groups in mammals. (5 marks)
ii) the reactions and the role of the glucose-alanine cycle.

(4 marks)
b) Show the reaction in which ammonia is formed from glutamate; include
any required cofactors. (3 marks)
c) Explain with a single diagram how the citric acid cycle and the urea cycle
overlap to form the Krebs bicycle. (3 marks)
2. a) Describe, by showing the chemical intermediates, the role of pyridoxal
phosphate (PLP) in the transamination of an amino acid. (7 marks)
b) Show the steps by which an intermediate of glycolysis can be converted
into serine. (4 marks)
c) An animal cell is capable of converting alanine into serine. What is the
shortest pathway using known enzymes by which this conversion could be accomplished? Show intermediates and cofactors. (4 marks)
3. Discuss the biomedical importance of DNA replication (15 marks)
4. Describe the mechanism of transcription (15 marks)
5. The template strand of a segment of double-stranded DNA contains the sequence:
(5’) CTT TGA TAA GGA TAG CCC TTC.
a) What is the base sequence of the mRNA that can be transcribed from this
strand? (4 marks)
b) What amino acid sequence could be coded by the mRNA base sequence in
(a), using only the first reading frame starting at the 5’ end? (Refer to the genetic code Table) (2 marks)
c) Suppose the other (complementary) strand is used as a template for
transcription. What is the amino acid sequence of the resulting peptide, again starting from the 5’ end and using only the first reading frame?
(3 marks)
d) In no more than three sentences describe a nonsense suppressor tRNA and
how it differs form a normal tRNA. (5 marks)
6. a) Describe the sequence of events between the transcription of an mRNA
for a secreted protein and the arrival of that protein in the lumen of the endoplasmic reticulum. (9 marks)
b) Polypeptide chain elongation in E.coli occurs by the cyclical repetition of
thee steps. What are the steps and what cellular components are necessary for each of them to occur? (6 marks)

Biochemistry Iii Question Paper

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