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Biochemistry Exam 1

102 Questions  I  By Andreazza

  
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1.  Which statement is incorrect about the nature of the hydrogen bond?
A.
B.
C.
D.
2.  If equal molar amounts of Na2HPO4 and Na3PO4 are mixed in water, calculate the resulting pH. The pKas of phosphoric acid are 2.1, 7.2, 12.4.
A.
B.
C.
D.
3.  Which of the following characteristics is not associated with the solvent water?
A.
B.
C.
D.
4.  Which of the following amino acids is the least water soluble at pH 7.0?
A.
B.
C.
D.
5.  Which amino acid would migrate the furthest toward the anode (positive electrode) during paper electrophoresis at pH 7.0?
A.
B.
C.
D.
6.  Calculate the pH that results when 0.75 mmol of HCl is added to 1.0 mmol of isoelectric histidine in 100 ml of water. The pKas for histidine are 1.8, 6.0, and 9.2.
A.
B.
C.
D.
7.  What volume of 2 N HCl is required to completely titrate a 4 mmol monosodium aspartate (Asp.Na) solution? For Asp.Na to be completely titrated we need 2 mols of HCl per mol of Asp.Na or 8mmolof HCl per 4mmol of Asp.Na.  mmol HCl = VHClxNHCl or V = 8mmol/2M = 
A.
B.
C.
D.
8.  Quaternary structure is associated with
A.
B.
C.
D.
9.  Reaction of the peptide, ala-met-lys-ser, with phenylisothiocyanate (PITC) at pH 8.0 followed by mild acidification (first cycle of Edman chemistry):  
A.
B.
C.
D.
10.  Which factors will influence the native conformation of a protein?
A.
B.
C.
D.
11.  The repeating secondary structures as found in beta-strands, beta-turns, and alpha-helices of folded proteins primarily result from
A.
B.
C.
D.
12.  Covalent forces
A.
B.
C.
D.
13.  Living systems are characterized by these, EXCEPT
A.
B.
C.
D.
14.  Carbon is essential for life is because
A.
B.
C.
D.
15.  One of these bonds is not capable of hydrogen bonding
A.
B.
C.
D.
16.  Oil in water
A.
B.
C.
D.
17.  The pH of a 0.05M solution of Ca(OH)2 is 
A.
B.
C.
D.
18.  The ionization constant of pure water is
A.
B.
C.
D.
19.  Which of the following pKAs represents the strongest acid?
A.
B.
C.
D.
20.  For a weak acid and its conjugated base the following is true
A.
B.
C.
D.
21.  If equal volumes of 0.8M sodium lactate and 0.4M lactic acid are mixed, and the pKa of lactic acid is 3.86, the final of the solution pH should be
A.
B.
C.
D.
22.  What would be the resulting pH following addition of 0.5 moles of sodium hydroxide to 1.0 mole of isoelectric alanine? The pKas for alanine are 2.4 and 9.7.
A.
B.
C.
D.
23.  The organ that controls the pH of the small intestine is?
A.
B.
C.
D.
24.  Which statement is INCORRECT about the classification of amino acids?
A.
B.
C.
D.
25.  An isoelectric amino acid was dissolved in water and the resulting pH was approximately 7.6. What amino acid would possess this property?
A.
B.
C.
D.
26.  Which of the following peptides would absorb the most light centered at 280 nm?
A.
B.
C.
D.
27.  For the amino acids histidine, alanine, and aspartic acid, list the amino acids in order of increasing isoelectric points.
A.
B.
C.
D.
28.  An isoelectric amino acid was dissolved in water and the resulting pH was approximately 10.7 . What amino acid would possess this property?
A.
B.
C.
D.
29.  Which statement is CORRECT about the peptide ala-ser?
A.
B.
C.
D.
30.  Fibrous proteins, such as collagen, have which of the following properties?
A.
B.
C.
D.
31.  The tertiary structure of a protein is usually a result of which of the following interactions?
A.
B.
C.
D.
32.  The information needed to define the structure of a protein is essentially contained in
A.
B.
C.
D.
33.  Determine the amino acid sequence of the following oligopeptide from the experimental data below 1. The amino acid composition is found to be ala, lys, phe, met, cys, trp 2. Treatment with carboxypeptidase results in tryptophan and a peptide 3. CNBr treatment yields a tetrapeptide and a dipeptide 4. Trypsin digestion produces an amino acid and a pentapeptide with met on the amino end 5. Chymotrypsin digestion yields a dipeptide and a tetrapeptide
A.
B.
C.
D.
34.  If the following section of a polypeptide is folded into an alpha-helix, to which amino acid is the CARBONYL GROUP OF ALANINE noncovalently bonded? ala-ser-val-asp-glu-leu-gly
A.
B.
C.
D.
35.  What in incorrect about an alpha-helix?
A.
B.
C.
D.
36.  One of these is not used to separate the subunits in a protein
A.
B.
C.
D.
37.  One of these is not found in alpha helices
A.
B.
C.
D.
38.  Iodoacetate is used to
A.
B.
C.
D.
39.  The energy that ATP transfers to another molecule resides in the phosphate bonds. 
A.
B.
40.  The type of energy released in an exergonic reaction is known as activation energy. 
A.
B.
41.  Specific binding is a characteristic of the diverse molecules such as enzymes. 
A.
B.
42.  Living systems are not actively engaged in energy transformations.
A.
B.
43.  Our bones are composed mainly of weak intermolecular forces. 
A.
B.
44.  Calculate the net energy of electrolysis of water: 2H20(l) → 2H2(g) + O2(g)
A.
B.
C.
D.
45.  What type of forces stabilizes the biological structure of macromolecules? Are covalent bonds weaker than these interactions? 
A.
B.
C.
D.
46.  Which of the following statements is true:
A.
B.
C.
D.
E.
47.  Based on the properties of Hydrogen “bond”, put pentane, water and ethanol in order of their boiling points (from strongest to weakest).  Hint: these may or may not create H-bonds with their own molecules.
A.
B.
C.
D.
48.  Oxygen in water is a type of dipole-induced dipole.
A.
B.
49.  A Hydrogen atom interacts with a very electronegative atom to form an H-bond. 
A.
B.
50.  Living organisms can function better with Si-O than C-O bonds.
A.
B.
51.  When Water is mixed with a non-polar solute, its entropy increases. 
A.
B.
52.  Water is an amphipathic molecule. 
A.
B.
53.  Weak forces bind free atoms together. 
A.
B.
54.  When HCl (strong acid) is added to water, the entropy will increase
A.
B.
55.  Detergent actually allows the surface tension of water to increase. 
A.
B.
56.  The more undisocciated the acid, the stronger it is. 
A.
B.
57.  What is the pH of 4.5 x 10-3 M solution of Ba(OH)2? Hint: Ba(OH)2→Ba+2 + 2OH-. Concentration of OH- is twice the concentration in Ba(OH)2.   2(4.5 x 10-3) = 9 x 10-3 = [OH-], [H+] = [1 x 10-14] / [9 x 10-3], [H+] = 1.1 x 10-12      Therefore, pH = -log[H+]   pH = -log (1.1 x 10-12)    pH = ________
A.
B.
C.
D.
58.  If the ratio of [HPO4-2] / [H2PO4-] in a muscle cell is 0.39, what is the internal pH of this cell? Hint: Phosphoric acid (H3P04) has three pKas (check powerpoint or textbook Chap 2). Choose only one pKa according to [HPO4-2] / [H2PO4-]. pH = pKa + log [A-]/[HA] pH = 7.2 + log (0.39) → pH = __________
A.
B.
C.
D.
59.  _____________ interactions are vital for cell membranes. 
60.  Micelles contain __________ends in contact with water and _________ends in the center. (answer, answer)
61.  As the ______ of a strong acid is a high value, its ______ should be low. (answer, answer)
62.  As an acid or a base is added, ___________ solutions will not easily change pH.
63.  The Henderson-Hasselbalch equation states that pH =______ when there are equal amounts or equivalents of an acid and its conjugate base.
64.  Which component in an amino acid will determine its identity?
A.
B.
C.
D.
65.  Is hydration used to bind two amino acids? 
A.
B.
66.  At what pH an amino acid will be neutral in charge, without considering any ionization on the side chain? 
67.  How do you call a neutral amino acid? 
68.  There are four aromatic amino acids. 
A.
B.
69.  All twenty amino acids are chiral. 
A.
B.
70.  At neutral pH, amino acids can be positively or negatively charged. 
A.
B.
71.  In acidic conditions, amino groups will be protonated
A.
B.
72.  In basic conditions, Phe will be neutrally charged. 
A.
B.
73.  At pH = 14, glutamic acid is in cationic form.
A.
B.
74.  At pH = 1, the R group of acidic and basic amino acids are charged.
A.
B.
C.
D.
75.  At pKa value of an amino acid, there are equal amounts of acid and conj. base. 
A.
B.
76.  If the side group of Glu is ¾ dissociated, its pH is around 1.523 
A.
B.
77.  In a sequence of six residues, there are five peptide bonds. 
A.
B.
78.  Ala-Gly-Lys-Gln-Arg-Phe-Asp Hint: sense of directionality for peptide bond COO - →NH3+ What amino acids are the N-terminal and C-terminal? 
A.
B.
C.
D.
79.  Ala-Gly-Lys-Gln-Arg-Phe-Asp Hint: sense of directionality for peptide bond COO - →NH3+ How many pKa values does this peptide have? 
A.
B.
C.
D.
80.  Ala-Gly-Lys-Gln-Arg-Phe-Asp Hint: sense of directionality for peptide bond COO - →NH3+ What is the net charge of this peptide at pH = 6? 
A.
B.
C.
D.
81.  In a cation exchange bead: The bead will be mainly positively or negatively charged? 
A.
B.
82.  In a cation exchange bead: A mixture of His, Glu and Arg is added. Which one will elute first at pH = 5? 
A.
B.
C.
D.
83.  In a cation exchange bead: A mixture of His, Glu and Arg is added. One will elute first at pH = 5. If pH is increased to 7, which amino acid will be eluted next? 
A.
B.
C.
D.
84.  The pI of Arg can be found by taking the average of its first two pKa values. 
A.
B.
85.  The main function of iodoacetate is to promote the formation of disulfide bridges
A.
B.
86.  Ellman’s reagent is used to determine the concentration of thiol groups in a sample. 
A.
B.
87.  Edman’s reagent will modify the C-terminal residues of a peptide sequence. 
A.
B.
88.  Chymotrypsin mainly cleaves amino acids which absorb light at 260-280nm. 
A.
B.
89.  The presence of proteins can be determined when the solution turns purple. 
A.
B.
90.  The partial double bond character of a peptide bond allows free rotation. 
A.
B.
91.  In HPLC, amino acids are separated mainly based on their charges.
A.
B.
92.  A multimeric protein contains a few (~3) disulfide bridges. After treating it with 8M urea to separate amino acid chains, iodoacetate should be added next. 
A.
B.
93.  One way to determine the C terminal is by using carboxypeptidases. 
A.
B.
94.  What is this derivative called? 
95.  What reagent has been used?
96.  What type of analysis has been done? 
97.  What is the amino acid that has being modified
98.  Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg   Which of the following reagents will cleave this peptide into two fragments only?
A.
B.
C.
D.
99.  Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg Which of the above reagents will produce a peptide with a C-terminal homoserine lactone? And how many fragments will be produced?
A.
B.
C.
D.
100.  Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg What happens if Clostripain and Carboxypeptidase A are added?
A.
B.
C.
101.  Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg After 3 rounds with Edman’s reagent, which residue will be modified next with this same reagent?
A.
B.
C.
D.
102.  1. Amino acid analysis of a peptide shows the composition Ala5, Lys1, Phe1. 2. Reaction of the intact peptide with Edman’s reagent followed by acid hydrolysis liberates Ala. 3. Trypsin cleavage of the intact peptide gives a tripeptide and a tetrapeptide with compositions Ala3, Phe1 and Lys1, Ala2. 4. Reaction of the intact peptide with chymotrypsin yields a hexapeptide plus free Ala. What is the sequence of this peptide?  
A.
B.
C.
D.
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