Biochemistry Final Exam

Exam (elaborations) Biochemistry Final Exam Biochemistry Final Exam 1) Calculate the enthalpy of formation per mol of NH3: Bond energies: H2, 436k KJ/mol; N2, 945 KJ/mol, N-H, 391 KJ/mol a) -93 KJ b) -1080 KJ c) 1080 KJ d) 45 KJ e) -46.5 KJ 2) Membrane structures are held primarily by? (OR membrane fs in a lipid bilayer are held together primarily by?) a) Hydrophobic interactions b) Covalent bonds c) Ionic Interactions d) All of the Above 3) Which system corresponds to the intracellular buffer in humans? a. H2PO4 -/ HPO4 2-/ PO4 3- system b. CO2/HCO3/H2CO3 system c. All of Above d. None of Above 4) Which of the following has the best buffering capacity? a. 2M CH3COOH/ 2M CH3COOb. 0.2M CH3COOH/ 0.2M CH3COOc. 7M CH3COOH/ 7M CH3COO- 5) Which of the following statements is incorrect about the following amino acids? a. Phe and Ala are nonpolar b. His and Arg are basic c. Cys and Gly are polar d. Asp and Asn are acidic 6) Which of the following amino acids belong to the same group? a. leu, pro, ala, val b. his, arg, lys, glu c. gly, tyr, cys, pro d. asp, glu, asn, gln 7) 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 and amino acid and a pentapeptide with met on the amino end 5. Chymotrypsin digestion yields a dipeptide and a tetrapeptide a. trp-lys-met-cys-met-ala b. lys-ala-cys-phe-met-trp c. trp-ala-phe-cys-met-lys d. lys-met-cys-phe-ala-trp 8) What is the overall net charge of the following polypeptide at pH = 13? lys-lys-his-glu a. +2 b. 0 c. –2 d. 1 9) Place the following amino acids by increasing isoelectric points: his, ala, asp, lys, arg. a. asp, ala, lys, arg, his b. his, lys, arg, ala, asp c. arg, lys, ala, his, asp 10) Most non-basic and non-acidic isoelectric amino acids: a. give a basic solution in water b. give an acidic solution in water c. give a neutral solution in water 11) Which cannot be a component in an alpha helix? a. lys b. gly c. pro d. All are components 12) In beta keratin (composed of ala and gly) you will find: a. alternating ala & gly in opposite faces b. ala and gly on the same plane c. None of Above 13)The most abundant amino acids in collagen is: a. pro & gly b. gly & ala c. All of Above d. None of Above 14) Every third amino acid faces the crowded center of tropocollagen molecule. This amino acid is: a. gly b. pro c. Ala d. All of Above 15) All are globular proteins except: a. ribonuclease b. alpha-keratin c. transport protein 16)This is true of an alpha helix a. all carbonyl groups point in the same direction d. its has a pitch that is smaller than that of collagen b. the helix has axial polarity e. all of the above c. the helix is found in human keratin 17) Collagen is characterized by a. having long streches of gly-propro/ hyp c. has no lysine in its composition b. formula has repeats of abcdefg amino acids d. being made of alpha helices 18)Globular proteins are usually all EXCEPT a. Insoluble in water d. Hydrophobic side chains are exposed to the water b. Roughly spherical e. none are true c. Folded so that the hydrophobic amino acids are in the interior of the molecule 19)Membrane proteins differ from globular proteins in that a. membrane associated amino acids usually have polar side chains d. globular proteins are water insoluble b. membrane proteins are much more soluble in detergents than water e. All are true c. membrane proteins usually have more hydrophobic amino acids 20)Alpha keratin has a structure with a sequence that a. has 7 repetitive residues c. disulfide bridges connect the polypeptides b. the first and the fourth are nonpolar d. all of them 21)One of these is not found in collagen a. 3-hydroxyproline c. 5-hydroxylysine b. 4-hyrdroxyproline d. 3-hydroxy-glycine 22)The separation between two proximal beta strands of a beta sheet is wider in the? a. paralell arrangement c. the have the same separation b. antiparalell arrangement d. none of them 23)The unique composition of collagen is accommodated in a structure called a(n): a. -pleated sheet. d. coiled coils. b. triple helix. e. all are true c. helix-turn-helix motif 24)The rate constant for a third order reaction has the unit: a. M-1 b. M-1-s-1 c. s-1 d. M-2-s-1