L> Exam 3 Answer Key Chemisattempt 332 - Winter 1997Exam 3: Chapters 15, 16 - Answer Key1. (15 points) Write finish frameworks for the following:a) the dipeptide ValGln as it would certainly show up at pH 7b) ATP (adenosine 5"-triphosphate)c) glyceryl triacetate2. (15 points) a) If a sample of DNA is analyzed and also discovered to contain 32% A and also 18%G, what have to be the rest of the base composition?32% T and 18% Cb) Using simply the 20 common amino acids, how many various tripeptidescan be created?20 x 20 x 20 = 8,000c) In an electrophoresis experiment, which of the 20 prevalent aminoacids would certainly move in the direction of the anode (the negative electrode) at pH 9 ?Lys and Arg are the only amino acids that would certainly be positively chargedat pH 9. They have actually isoelectric points above 9.3. (15 points) The name for the amino acid threonine comes from itssimilarity in structure to the sugar D-threose, shown below.Write the structure for threonine in a Fischer estimate that clearlymirrors its similarity to D-threose. Identify each stereofacility in threonineas R or S. Only one various other amino acid (of the 20 prevalent ones in your table) has2 stereocenters. Which one? Write its framework with both stereocentersin the S configuration.4. (15 points) Several of the three-letter codes in the codon table canbe deduced by use of simple nucleic acid polymers that are easy to make.For example, if poly-U is fed to the bacteria E. coli, an excess of theamino acid phenylalanine appears. Exordinary.The codon UUU converts as PheWhat amino acids would certainly be expected from poly-G, poly-C, and poly-A?The codon GGG translates as GlyThe codon CCC translates as ProThe codon AAA equates as LysWhat amino acids would certainly be supposed from a constant alternating copolymerof A and C (i.e., ACACACACACACAC ) ?The codon ACA equates as ThrThe codon CAC converts as His5. (15 points) Consider an unwell-known heptapeptide consisting of thefollowing amino acids: Arg, Asp, His, Ile, Phe, Tyr, ValDeduce its primary framework from the following data:the N-terminus is Aspthe C-terminus is Phechymotrypsin cleaves it to a tripeptide and a tetrapeptide, A andBA has actually Ile at its N-terminus and Phe at its C-terminusB can be partly hydrolyzed to provide dipeptides Arg Val, AspArg andValTyrAsp Arg Val Tyr Ile His PheUse the amino acids in this peptide to show the adhering to aspectsof tertiary structure. Draw just the specific side chain frameworks associated.a) ionic attractivity b) H-bondingseveral possibilities, including: 6. (10 points) The framework of the male hormone androsterone is shownbelow. Complete the framework on the best by effectively locating each ofthe seven substituents that are especially shown on the left structure.Identify each substituent as either axial or equatorial (usage A or E).all substituents are axial7. (15 points) Glutamic acid has 2 carboxylic acid teams through differentpKa worths.

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The structure is shown in its totally protonated form listed below, withits three pKa values. Referring to the pH diagram listed below, create the structuresof the significant develops that would certainly be intended in solution within each of thepH ranges noted A, B, C, and D.Exordinary why the 2 carboxylic acid groups have actually various pKa worths.The -COOH team closer to the -NH3+ team is a stronger acid becauseof the electron-withillustration effect of the -NH3+ team.