Structural Biochemistry 1 (BCHS3101)
BSc, Biochemistry - BCHS
Semester: First Semester
Level: 300
Year: 2018
REPUBLIC OF CAMEROON THE UNIVERSITY OF BAMENDA
Peace-Work-Fatherland
P. O. BOX 39 Bambili
School/Faculty:Science Department:_Biochemistry Lecturer(s): Dr Nantia & Pr
Mbouobda____
Course Code: _BCHS3101_______ Course Title: Structural Biochemistry I__
Date: _Febuary 2018_______Halls: __ ________Time: __
Instructions: ___Answer questions in ordering manner and do not miss different exercises.
Exercise 1 (7 marks)
A MCQ (4.5 marks)
1) Of the 20 standard amino acids, only….is not optically active. The reason is that its side chain …..
a) alanine; is a simple methyl group b) glycine; is a hydrogen atom c) glycine; is unbranched d) lysine; contains
only nitrogen
2) All of the amino acids that are found in proteins, except for proline, contain a(n):
a) amino group. b) carbonyl group. c) carboxyl group. d) ester group, e) thiol group.
3) Which of the following statements about aromatic amino acids is correct?
a) All are strongly hydrophilic, b) Histidine’s ring structure results in its being categorized as aromatic or basic,
depending on pH. c) On a molar basis, tryptophan absorbs more ultraviolet light than tyrosine. d) The major
contribution to the characteristic absorption of light at 280 nm by proteins is the phenylalanine R group. e) The
presence of a ring structure in its R group determines whether or not an amino acid is aromatic.
4) Which of the following statements about cystine is correct?
a) Cystine forms when the —CH
2
—SH R group is oxidized to form a — CH
2
—S—S—CH
2
— disulfide bridge
between two cysteines, b) Cystine is an example of a nonstandard amino acid, derived by linking two standard
amino acids. c) Cystine is formed by the oxidation of the carboxylic acid group on cysteine. d) Cystine is
formed through a peptide linkage between two cysteines. e) Two cystines are released when a —CH
2
—S—S—
CH2— disulfide bridge is reduced to —CH2—SH.
5) The uncommon amino acid selenocysteine has an R group with the structure —CH2—SeH (pK
a
» 5). In an
aqueous solution, pH = 7.0, selenocysteine would:
a) be a fully ionized zwitterion with no net charge. b) be found in proteins as d-selenocysteine.
c) never be found in a protein, d) be nonionic, e) not be optically active.
6) Amino acids are ampholytes because they can function as either a(n):
a) acid or a base. b) neutral molecule or an ion. c) polar or a nonpolar molecule, d) standard or a
nonstandard monomer in proteins. e) transparent or a light-absorbing compound.
7) Titration of valine by a strong base, for example NaOH, reveals two pK’s. The titration reaction occurring at
pK
2
(pK
2
= 9.62) is:
a) —COOH + OH'-> —COO
-
+ H
2
O. b) —COOH + —NH
2
-> - COO
-
+—NH
2
+
. c)— COO
-
+ —
NH2 -> —COOH + —NH
2
. d) —NH
3
+
+ OH' -> —NH2 + H2O. e) —NH
2
+ OH" -> —NH’ + H2O.
8) For amino acids with neutral R groups, at any pH below the pl of the amino acid, the population of amino
acids in solution will have:
a) a net negative charge. b) a net positive charge. c) no charged groups, d) no net charge, e) positive and
negative charges in equal concentration.
9) The element found in all amino acids that is not found in carbohydrates is
a) Sulphur (b) Carbon (c) Oxygen (d) Hydrogen (e) Nitrogen (f) a and b
B) fill the table below (2.5 mrks)
Definition Example (structure and name) Function
Standard amino acid
Essential amino acid
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Exercise 2 (13 marks)
Mrs Wendy has been given the biomolecule X glycylalanylprolyltyrosylmethionylthreonine
1)
Help propose the one letter nomenclature of X (1.5 mrk)
2)
What could she give as structure of X? (3 mrks)
3)
What could be the nature of X (1 mrk)
4)
Give with justifications (in a table) 4 properties of X (2 mrks)
5)
What could be the changes on X structure if it is treated with increasing H
+
solution? (3 mrks)
6)
Mrs Wendy proposes as X pl 4.6. Is it correct? (2 mrks)
Given:
7)
Mrs Wendy intubates X in an electrophoretic field containing phosphate buffer (C 0.0IM, pH 7.0). Help
her determining any possible mobility of X. (1.5 mrk)
Exercise 2 (10 marks)
1)
Nucleic acids are vital biomolecules for living organisms. In a table, give 4 functions of nucleic acids
with example (3 mrks).
2)
Compare the systematic names and functions of cGMP and ATP (3 mrks)
3)
A student was giver, a biomolecule 3’-pGpApUpTpC-5’
a)
Can such a molecule occur naturally? Justify your answer (1 mrk)
b)
Give the developed structure of the molecule (2 mrks)
c)
Give 2 properties of the molecules (1 mrk)
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