1 Which of structures below stands for D-ribose? Answer = (b) CH2OH CHO HCOH HCOH e) d) c) b)a)HCOH HCOH HCOH HOCH CHO CH2OH HCOH HOCH HCOH CHO CH2OH HCOH HCOH HOCH CHO CH2OH HCOH HCOH HCOH CHO CH2OH 2 Hydrophobic interactions most likely occur between the R groups of which of the following amino acids? a) arginine and histine b) leucine and methionine c) phenylalanie and threonine d) valine and tyrosine 3 The three-dimensional conformation of a protein may be strongly influence by amino acid residues that are very far apart in sequence. This relationship is in contrast to secondary structure, where the amino residues are: a) always side by side b) generally near each other in sequence c) generally on different polypeptide strands d) generally near the polypeptide chain’s amino terminus or carboxyl terminus e) restricted to only about seven of the twenty standard amino acids found in proteins4 Myoglobin mainly consists of . a) α helix b) β sheet c) β turn d) a) and b) 5 Amino acid analysis of an oligopeptide seven residues long gave Asp Leu Arg Met Phe Tyr The following facts were observed: a. Trypsin treatment had no apparent effect. b. The phenylthiohydantoin released by Edman degradation was c. Brief chymotrypsin treatment yielded several products including a dipeptide and a tetrapeptide. The amino acid composition of the tetrapeptide was Leu, Arg, and Met. d. Cyanogen bromide treatment yielded a dipeptide, a tetrapeptide, and free Arg. What is the amino acid sequence of this heptapeptide? a) N- Arg Asp Tyr Met Leu Met Phe b) N- Arg Asp Tyr Met Met Leu Phe c) N- Phe Asp Tyr Met Leu Met Arg d) N- Phe Asp Tyr Met Met Leu Phe e) N- Tyr Asp Arg Met Leu Met Phe 6 functions to prevent intramolecular and intermolecular aggregates of unfolded proteins. a) protein precursor b) ligand c) structural motif d) molecular chaperone7 The H+ concentration of 0.5M NaOH is : the H+ concentration of 0.5M acetic acid is ( assume the decrease in the concentration of acetic acid due to dissociation is negligible: K’ of acetic acid = 1.74 x 10-5 ). a) 2 x 10-14 M 0.5 M b) 0.5 M 2.95 x 10-3 M c) 2 x 10-14 M 9.33 x 10-4 M d) 2 x 10-14 M 2.95 x 10-3 M e) 0.5 M 9.33 x 10-4 M 8 In the binding of oxygen to hemoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as . a) hyperbolic b) sigmoidal c) linear with a positive slope d) linear with a negative slope e) random 9 A fetus obtains oxygen from maternal circulation via the placenta. This biological process can be realized because a) Fetal hemoglobin (HbF) has a higher oxygen affinity than maternal hemoglobin (HbA) does. b) The concentration of BPG is higher in fetal erythrocytes. c) BPG could bind more tightly to deoxyHbA than to deoxyHbF. d) a) and b) e) a) and c) . 10 Water molecules bind to one another by means of hydrogen bonds. Additionally, water is able to form hydrogen bonds with each type of functional group except? a) Lipids b) Amino groups (N-H) c) Hydroxyl groups (O-H) d) Carbonyl groups (C O) e) None of above11 Two monosaccharides combine to form disaccharidesor polysaccharides. This involves the OH group of one monosaccharide forming an ester linkage with the anomeric carbon of the second monosaccharide. This type of bond is called: a) Glycosidic b) Branching c) N-glycosidic bond d) O-glycosidic bond 12 Proteins must fold into their final structures to be functional. Which of the following statements are not true? a) Folding begins with disulfide bond formation; b) Structural motifs such as αα or ββ act as seeds around which the rest of the protein folds; c) Helper proteins called chaperones may assist protein folding; d) Hydrophobic amino acids are buried in the interior. 13 Which of the following is correct with respect to the amino composition of all proteins? a) Proteins with the same molecular weight have the same amino acid composition b) Proteins contain at least one each of the twenty different standard amino acids. c) Larger proteins have a more uniform distribution of amino acids than smaller proteins. d) Proteins with different functions usually differ significantly in their amino acid compositon e) The average molecular weight of an amino acid in a protein increases with the size of the protein. 14. The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In the second step, this gel is turned at a right angle, placed on another gel, and a second electric current is applied. In this second step: a) the individual bands undergo a second, more intense iselectric focusing. b) the individual bands become stained so that the isoelectric focus patterns can be visualized. c) the individual bands become visualized by interacting with protein-specific antibodies in the second gel. d) the proteins in the bands separate more completely because the second electric current is in the opposite polarity to the first current. e) proteins with similar isoelectric points become further separated according to their molecular weights by an SDS gel.15. Compare the following sequences taken from four different proteins, and select the answer that best characterizes their relationships. a) Protein 4 is the protein that shows the greatest overall homology to protein 1. b) The portions of amino acid sequence shown suggest that these proteins are completely unrelated. c) Based only on sequences in column B, protein 4 reveals the greatest evolutionary divergence. d) Comparing proteins 1 and 2 in column A reveals that these two proteins have diverged the most