PHR 911 Study Questions With Complete Solutions

Which one of the four classes of biologically important molecules does insulin belong to? a. carbohydrates b. proteins c. nucleic acids d. lipids correct answer: b. proteins Which of the following is true? a. the amino acid may be any of the nonpolar, aliphatic amino acids b. the first pKa represents protonation/deprotonation of the amine c. the amino acid cannot be a member of the sulfur-containing classification d. the side chain contains a carboxylate functional group e. the side chain contains an amine functional group correct answer: a. the amino acid may be any of the nonpolar, aliphatic amino acids Of the 20 standard amino acids, only ________ is not optically active. The reason is that its side chain ________. a. Ala; is a simple methyl group b. Gly; is a hydrogen atom c. Ile; is unbranched d. Lys; contains a nitrogen e. Pro; forms a covalent bond with the side chain correct answer: b. Gly, is a hydrogen bond Two amino acids of the standard 20 amino acids contain sulfur atoms. They are: correct answer: methionine (Met, M) and cysteine (Cys, C) All of the amino acids described in class, except proline (Pro), contain a: a. primary amino group b. carbonyl group c. carboxyl group d. ester group e. thiol group correct answer: a. primary amino group The chirality of an amino acid results from the fact that its alpha carbon: a. has no net charge b. is a carboxylic acid c. is bonded to four different chemical groups d. is in the D-configuration for those incorporated into proteins e. is symmetric correct answer: c. is bonded to four different chemical groups The amino acid Glu has an R group that makes Glu: a. a zwitterion with no net charge at pH=7 b. found in proteins in the D-configuration c. never found in proteins d. nonionic e. function in acid/base catalysis correct answer: e. function in acid/base catalysis Titration of valine by a strong base, for example NaOH, reveals two pKs. The titration reaction occurring at pK2 (pK2=9.62) is: a. -COOH + OH(-) -- -COO(-) + H2O b. -COOH + -NH2 -- -COO(-) + -NH2(+) c. -COO(-) + -NH2(+) -- -COOH + NH2 d. -NH3(+) + -OH(-) -- -NH2 + H2O e. -NH2 + OH(-) -- -NH(-) + H2O correct answer