MITES ame Practice Midterm Exam 200 points total 75 minutes Multiple hoice (3 pts each 30 pts total) Mark your answers in the space to the left: 1. Amphipathic molecules have regions that are: a) polar b) nonpolar c) hydrophilic d) hydrophobic e) all of the above 2. Eukaryotic cells have: a) a cell membrane b) a nucleus c) complex organelles d) all of the above e) none of the above 3. The pk a values for phosphoric acid are 2.14, 6.86, and 12.4. The pk b values are: a) 2.14, 6.86, and 12.4 b) 16.14, 20.86, and 26.4 c) -2.14, -6.86, and -12.4 d) 1.60, 7.14, and 11.86 e) 1.13, 2.04, and 6.54 4. Which of the following weak noncovalent forces would T be present in an aqueous solution of a charged polar compound: a) Van der Waals interactions b) ydrogen bonds c) ydrophobic interactions d) Ionic interactions 5. There are nucleotides per turn, each Å (Distance) apart in the naturally occurring form of double helical DA. a) 11, 34, B b) 10.5, 3.4, A c) 10.5, 34, Z d) 12, 26, A e) 10.5, 3.4, B 1
MITES 6. Shown below are four possible base pairing schemes between the bases guanine (G) and uracil (U). Remember that G-U base pairs form in RA. X represents 1 of ribose. Which base pairing scheme exhibits valid hydrogen bonding? a) G U b) G X X X U X X U X U c) G X d) G X 7. What is the tripeptide shown below? 3 + 2 2 2 2 2 S 3 a) Phe-Gln-Met b) Phe-Asn-Met c) Tyr-Gln-Met d) Tyr-Asn-Met e) none of the above 8. Which of the amino acids below has a side chain that is polar and charged? a) alanine b) tyrosine c) aspartate d) threonine e) none of the above 9. Which of the amino acids below has a side chain that is nonpolar and charged? a) alanine b) phenylalanine c) glutamate d) histidine e) none of the above 2
MITES 10. Which of the amino acids below has a side chain that is aromatic? a) phenylalanine b) tyrosine c) tryptophan d) all of the above e) none of the above True/False (3 pts each 30 pts total) Please mark your answers in the space to the left: 11. Monosaccharides and polysaccharides are types of proteins. 12. Water s low specific heat is a direct result of hydrogen bonding. 13. At the half-equivalence point of a monoprotic acid titration curve, [A] = [A ] and p = pk a. 14. A 0.01-M solution of l would have p = 1. 15. ydrophobic interactions occur between lipid molecules. 16. In the titration of 100 ml of a 0.1-M phosphoric acid solution, 5 ml of a 2-M a solution would be one equivalent. 17. All amino acids contain an amino group and a hydroxyl group. 18. nly L-amino acids are used in biologically produced proteins. 19. The zwitterionic form of lysine has a charge of +1. 20. Serine and methionine both contain sulfur atoms. Short Answer Please show your work--partial credit will be given. (55pts) 3
MITES 21. A base titration curve of maleic acid (pk a s = 2.00, 6.26) is shown below. Fill in the empty boxes on the x- and y-axes with numerical values. (6pts) Titration of Maleic Acid p 0 0 2 Molar Equivalents of a 22. Give one example of a protein and one example of a nucleic acid. (2pts) protein:_ nucleic acid: 23. n the molecules below, fill in labels to identify the functional groups. (6pts) P 2 2 3 + 2 S 24. For each molecule below, write the total number of chiral centers and circle each one. (5pts) 4
MITES 2 ribose chorismate 2 25. ircle and label the functional groups on the two molecules below. ote: carbonyl is insufficient; please be more specific. (6pts) 2 P 26. omplete the table below. For the two biological polymers listed below, give the general name for the monomer and polymer of each. (4pts) Monomer Protein ucleic Acid Polymer Polypeptide ucleic Acid 27. Which two weak noncovalent interactions will occur between hydrophilic molecules? (4pts) 28. Identify whether amino acids below are in the L or D form. (6pts) 5
MITES 3 + _ 3 + _ 2 3 3 2 29. Determine whether the following molecules S or R stereoisomers (12 pts): 30. In no more than two sentences, describe the main purpose behind the use of RA interference (RAi) in molecular biology today? (4pts) 6
Problems Please show your work partial credit will be given. (85pts) 31. (7 pts) For each pair of molecules listed below, state whether hydrogen bonding will occur between the two molecules and if so show how this would occur. Molecules -bonding? (Y/) If Yes, show -bonding a) 3 3 b) 3 3 c) 3 3 32. (8 pts) pk a data for glycine are shown below. pk a1 arboxyl 2.34 pk a2 Amino 9.60 a) A buffer is prepared by combining 1 mole of fully-protonated glycine ( 3 + - 2 -) and 0.5 mole a in 1 L of water. What is the p of the buffer? 7
b) 1 L of a 1M a solution is added to this buffer. What is the new p? 33. (15 pts) Using only 2 P 4 and P 4 3 how many moles of each would you add to prepare 1 L of a 0.11 M buffer at p 7.9? 3 P 4 + 2 2 P 4 + 3 + (Rxn1) pk a1 = 2.1 2 P 4 + 2 P 4 2 + 3 + (Rxn2) pk a2 = 6.9 P 4 2 + 2 P 4 3 + 3 + (Rxn3) pk a3 = 12.4 [A-] + [A] =.11 7.9 = 6.9 + log ([A-]/[A]) [A-] =.1 [A] =.01 2P4- =.06 P4 =.05 8
34. (20 pts) The structure of arginine and its K a values are given below. Draw an schematic titration curve, identifying the axis with appropriate scale, pk s, pi, and draw the specie that predominates at each endpoint, along with the net charge for each. K a1 (carboxyl) 10-2 K a2 (amino) 10-9 K ar (side chain) 10-12 3 + 2 2 2 2 2 + _ 9
35. Draw a polypeptide chain containing the following amino acid sequence: Asn-ys-Glu-Lys-Tyr. ircle the peptide bonds and mention the functional group they represent. What is the net charge of the polypeptide at p = 1.0, 5.0, 7.0, 9.5, 13? (20pts) 10
36. Draw a sequence of 3 DA nucleotides: AG. ircle the phosphodiester bonds and draw out the bases. Please state the directionality of the strand. (15pts) 11
Supplementary Material Ka 1: 1.6 pka 2 :1.9 pka R :10.7 Ka 1 : 2.19 pka 2 : 9.2 Ka 1 : 2.09 pka 2 : 9.1 Ka 1: 2 pka 2 :9.9 pka R :3. Ka 1: 2.9 pka 2 :9.5 pka R : Ka 1 1.8 pka 2 9.3 pka R 6 pka 1 : 2.14 pka 2 : 8.4 Ka 1 : 2.17 pka 2 : 9.1 Ka 1: 2.2 pka 2 :9.2 pka R :10. Ka 1: 2 pka 2 :9.1 pka R :10.54 Ka 1: 1.8 pka 2 :9 pka R :12.5 pka 1 : 2.35 pka 2 : 9.8 Ka 1 : 2.35 pka 2 : 9.9 pka 1 : 1.95 pka 2 : 10.5 pka 1 : 2.29 pka 2 : 9.7 Ka 1 : 2.33 pka 2 : 9.7 pka 1 : 2.32 pka 2 : 9.8 pka 1 : 2.13 pka 2 : 9.3 Ka 1 : 2.20 pka 2 : 9.3 pka 1 : 2.46 pka 2 : 9.4 12
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