Amino Acids and Proteins - Questions with Answers | CHEM 1152K, Exams of Chemistry

Download Amino Acids and Proteins - Questions with Answers | CHEM 1152K and more Exams Chemistry in PDF only on Docsity! General, Organic, and Biological Chemistry, 4e (Timberlake) Chapter 19 Amino Acids and Proteins 19.1 Multiple-Choice Questions 1) Which of the following is NOT a function of proteins? A) provide structural components B) stores the genetic information of a living organism C) movement of muscles D) catalyze reactions in the cells E) transport substances through the bloodstream Answer: B Objective: 19.1 Global Outcomes: GO2 2) Collagen, a protein found in tendons and cartilage, would be classified as a __________ protein. A) catalytic B) structural C) transport D) storage E) hormone Answer: B Objective: 19.1 Global Outcomes: GO2 3) Wool is primarily made up of A) protein. B) carbohydrate. C) globin. D) triacylglycerols. E) enkephalin. Answer: A Objective: 19.1 Global Outcomes: GO2 4) Sucrase, the protein that facilitates the hydrolysis of sucrose, would be classified as a __________ protein. A) transport B) hormonal C) catalytic D) structural E) contractile Answer: C Objective: 19.1 Global Outcomes: GO2 1 Copyright © 2013 Pearson Education, Inc. 5) The structural formulas of amino acids are the same EXCEPT for the A) carboxyl group. B) alpha carbon. C) amino group. D) side (R) group. E) hydrogen bonding. Answer: D Objective: 19.1 Global Outcomes: GO2 6) The following amino acid R group chain is A) polar. B) hydrophobic. C) hydrophilic. D) acidic. E) basic. Answer: B Objective: 19.1 Global Outcomes: GO2 7) Which of the following would be most likely to be deficient in at least one essential amino acid? A) eggs B) milk C) beans D) steak E) ham Answer: C Objective: 19.1 Global Outcomes: GO7 8) Amino acids that are not synthesized in the body and must be obtained from the diet are called A) essential. B) polar. C) nonpolar. D) complete. E) incomplete. Answer: A Objective: 19.1 Global Outcomes: GO7 2 Copyright © 2013 Pearson Education, Inc. 16) What is the structural formula of glutamic acid (pI = 3.2) at pH = 1? A) B) C) D) E) Answer: E Objective: 19.2 Global Outcomes: GO2 17) Consider a mixture of the amino acids lysine (pI = 9.7), tyrosine (pI = 5.7), and glutamic acid (pI = 3.2) at a pH 5.7 that is subjected to an electric current. __________ will migrate towards the positive electrode(+). A) Lysine B) Tyrosine C) Glutamic acid D) All of the amino acids Answer: C Objective: 19.2 Global Outcomes: GO2 5 Copyright © 2013 Pearson Education, Inc. 18) Consider a mixture of the amino acids lysine (pI = 9.7), tyrosine (pI = 5.7), and glutamic acid (pI = 3.2) at a pH 5.7 that is subjected to an electric current. __________ will remain stationary. A) Lysine B) Tyrosine C) Glutamic acid D) All of the amino acids Answer: B Objective: 19.2 Global Outcomes: GO2 19) In a typical amino acid zwitterion, the carboxylate end is A) positively charged. B) negatively charged. C) neutral. D) soluble in a nonpolar solvent. E) attached to an amine. Answer: B Objective: 19.2 Global Outcomes: GO2 20) The R group for serine is –CH2OH. As a zwitterion, serine has the structural formula A) B) C) D) E) Answer: E Objective: 19.2 Global Outcomes: GO2 21) Which of the following functional groups of an amino acid would be in the ionized state at 6 Copyright © 2013 Pearson Education, Inc. high pH? A) B) -CH2OH C) -CH3 D) E) Answer: A Objective: 19.2 Global Outcomes: GO2 7 Copyright © 2013 Pearson Education, Inc. 27) Which of the following shows all of the tripeptides that can be formed from one molecule each of lysine (Lys), threonine (Thr), and histidine (His)? A) Lys-Thr-His B) Lys-Thr-His, Lys-His-Thr, His-Thr-Lys, His-Lys-Thr, Thr-Lys-His, Thr-His-Lys C) Lys-Thr-His, Lys-His-Thr, His-Lys-Thr, Thr-His-Lys D) Lys-Thr-His, Lys-His-Thr, His-Lys-Thr E) Lys-Thr-His, Lys-His-Thr Answer: B Objective: 19.3 Global Outcomes: GO2 28) A peptide bond contains which kind of functional group? A) alcohol B) amine C) amide D) carboxylic acid E) ketone Answer: C Objective: 19.3 Global Outcomes: GO2 29) A chain made of more than 50 amino acids is usually referred to as a(n) A) peptide. B) protein. C) enzyme. D) globulin. E) hormone. Answer: B Objective: 19.4 Global Outcomes: GO2 30) Which of the following is an example of a secondary protein structure? A) dipeptide B) triglyceride C) a helix D) amino acid E) fatty acid Answer: C Objective: 19.4 Global Outcomes: GO2 10 Copyright © 2013 Pearson Education, Inc. 31) The α helix of the secondary structure of a protein is held together by __________ between two widely separated parts of a protein chain. A) hydrogen bonds B) disulfide bridges C) salt bridges D) hydrophilic interactions E) hydrophobic interactions Answer: A Objective: 19.4 Global Outcomes: GO2 32) In the β-pleated sheet secondary structure of a protein, two or more amino acid sequences in separate parts of the protein are held together A) in a coil, by hydrogen bonding. B) in random order, due to hydrophobic interactions. C) in a triple helix. D) in a double helix. E) in a zig-zag conformation, by hydrogen bonding. Answer: E Objective: 19.4 Global Outcomes: GO2 33) Enkephalins are polypeptides that have A) a sweet taste. B) a bitter taste. C) extra caloric value. D) pain-killing properties. E) hormone activity. Answer: D Objective: 19.4 Global Outcomes: GO7 34) Enkephalins, naturally produced opiates in the body, are found in A) muscles and bone tissue. B) brain and kidney tissue. C) thalamus and spinal cord tissue. D) heart and lung tissue. E) pancreas and liver tissue. Answer: C Objective: 19.4 Global Outcomes: GO7 11 Copyright © 2013 Pearson Education, Inc. 35) The interactions that are important in the secondary structure of a protein are A) hydrogen bonds. B) hydrophobic interactions. C) disulfide bonds. D) salt bridges. E) peptide bonds. Answer: A Objective: 19.4 Global Outcomes: GO2 36) Which of the following is a secondary protein structure? A) α helix B) Ser-Met-Ala-Gly-Ile C) disulfide bond D) salt bridges E) hydrophobic interactions Answer: A Objective: 19.4 Global Outcomes: GO2 37) The secondary structure of collagen is distinguished by A) single α helix strands. B) double α helix strands. C) many α helixes wound into fibrils. D) a braided triple helix. E) many glycoside links. Answer: D Objective: 19.4 Global Outcomes: GO2 38) In insulin, two peptide chains are held together in a single unit by A) disulfide bridges. B) hydrogen bonds. C) salt bridges. D) a prosthetic group. E) a β-pleated sheet. Answer: A Objective: 19.4 Global Outcomes: GO2 12 Copyright © 2013 Pearson Education, Inc. 46) Disulfide bonds in a protein chain connect A) an amine and a carboxylic acid group. B) an alcohol and a carboxylic acid group. C) tryptophan and alanine residues. D) two cysteine residues. E) two asparagine residues. Answer: D Objective: 19.5 Global Outcomes: GO2 47) What kinds of interactions are NOT part of tertiary protein structure? A) peptide bonds B) disulfide bonds C) hydrophilic interactions D) salt bridges E) hydrophobic interactions Answer: A Objective: 19.5 Global Outcomes: GO2 48) The function of myoglobin is to A) carry vitamins in the blood. B) carry oxygen in the blood. C) support the skeletal muscles. D) carry oxygen in the muscle. E) provide strength in cartilage. Answer: D Objective: 19.5 Global Outcomes: GO2 49) In sickle-cell anemia, the hemoglobin molecules A) come apart into separate chains. B) enlarge to twice normal size. C) clump together into insoluble fibers. D) dissolve in the plasma. E) undergo crenation. Answer: C Objective: 19.5 Global Outcomes: GO2 15 Copyright © 2013 Pearson Education, Inc. 50) Acids and bases denature a protein by disrupting A) peptide bonds and ionic bonds. B) amide bonds and alkene bonds C) hydrophobic interactions and peptide bonds. D) ionic bonds and hydrophobic interactions. E) ionic bonds and hydrogen bonds. Answer: E Objective: 19.6 Global Outcomes: GO2 51) Heat denatures a protein by disrupting A) ionic bonds and peptide bonds. B) hydrophobic bonds and hydrogen bonds. C) peptide bonds and hydrophobic bonds. D) disulfide bonds and peptide bonds. E) hydrogen bonds and disulfide bonds. Answer: B Objective: 19.6 Global Outcomes: GO2 52) Denaturation of a protein A) changes the primary structure of a protein. B) disrupts the secondary, tertiary, or quaternary structure of a protein. C) is always irreversible. D) hydrolyzes peptide bonds. E) can only occur in a protein with quaternary structure. Answer: B Objective: 19.6 Global Outcomes: GO2 53) One heavy metal that can cause denaturation of a protein is A) silver. B) sodium. C) barium. D) iron. E) calcium. Answer: A Objective: 19.6 Global Outcomes: GO2 16 Copyright © 2013 Pearson Education, Inc. 54) Heavy metals denature proteins by A) releasing amino acids. B) disrupting hydrophobic interactions. C) changing the pH of the protein solution. D) changing the temperature of the protein solution. E) disrupting disulfide bonds. Answer: E Objective: 19.6 Global Outcomes: GO2 55) An acid can denature a protein by A) agitating the protein chains. B) disrupting hydrogen bonds between R groups chains. C) disrupting hydrophobic interactions within a protein chain. D) removing helping molecules such as heme. E) breaking disulfide bridges. Answer: B Objective: 19.6 Global Outcomes: GO2 19.2 Bimodal Questions 1) Immunoglobulin, a protein that stimulates immune responses, would be classified as a __________ protein. A) transport B) structural C) storage D) protection E) catalytic Answer: D Objective: 19.1 Global Outcomes: GO2 2) What amino acids have polar R groups that are attracted to water? A) hydrophilic B) hydrophobic C) nonpolar D) aromatic E) hydrocarbon Answer: A Objective: 19.1 Global Outcomes: GO2 17 Copyright © 2013 Pearson Education, Inc. 10) In digestion, proteins are broken down into amino acids by a(n) __________ reaction. A) saponification B) reduction C) hydrolysis D) oxidation E) denaturation Answer: C Objective: 19.6 Global Outcomes: GO2 19.3 Short Answer Questions 1) Collagen can be classified as a __________ protein. Answer: structural Objective: 19.1 Global Outcomes: GO2 2) The protein that transports oxygen in the blood is __________. Answer: hemoglobin Objective: 19.1 Global Outcomes: GO2 3) Proteins that stimulate immune response are known as __________. Answer: immunoglobulins Objective: 19.1 Global Outcomes: GO2 4) Amino acids that are not synthesized in the body but must be ingested with the diet are called __________ amino acids. Answer: essential Objective: 19.1 Global Outcomes: GO2 5) A zwitterion of any amino acid has a net charge of __________. Answer: zero Objective: 19.2 Global Outcomes: GO2 6) The isoelectric point for any amino acid is the pH at which the amino acid has a net charge of __________. Answer: zero Objective: 19.2 Global Outcomes: GO2 20 Copyright © 2013 Pearson Education, Inc. 7) Electrophoresis is a laboratory technique for separating amino acids using their different __________. Answer: isoelectric points Objective: 19.2 Global Outcomes: GO2 8) Write the zwitterion of glycine. Answer: Objective: 19.2 Global Outcomes: GO2 9) Circle the peptide bond in this structure. Answer: Objective: 19.3 Global Outcomes: GO2 19.4 True/False 1) Hemoglobin is a transport protein. Answer: TRUE Objective: 19.1 Global Outcomes: GO2 2) Insulin is a transport protein. Answer: FALSE Objective: 19.1 Global Outcomes: GO2 21 Copyright © 2013 Pearson Education, Inc. 3) Zwitterions have an overall positive charge. Answer: FALSE Objective: 19.2 Global Outcomes: GO2 4) The dipeptide abbreviated as Gly-Lys is the same as the dipeptide abbreviated as Lys-Gly. Answer: FALSE Objective: 19.3 Global Outcomes: GO2 5) Sickle-cell anemia is caused by a change in the primary structure of a subunit of the hemoglobin protein. Answer: TRUE Objective: 19.4 Global Outcomes: GO2 6) The peptide sequence Gly-Gly-Gly gives the primary structure of a tripeptide. Answer: TRUE Objective: 19.4 Global Outcomes: GO2 7) Disulfide bonds stabilize the tertiary structure of a protein. Answer: TRUE Objective: 19.5 Global Outcomes: GO2 8) Lysine and glutamic acid form hydrophobic interactions. Answer: FALSE Objective: 19.5 Global Outcomes: GO2 9) Upon hydrolysis the dipeptide abbreviated as Gly-Lys will yield the same products as the dipeptide abbreviated as Lys-Gly. Answer: TRUE Objective: 19.6 Global Outcomes: GO2 10) Lead ions disrupt hydrophobic interactions. Answer: FALSE Objective: 19.6 Global Outcomes: GO2 22 Copyright © 2013 Pearson Education, Inc. Would an amino acid with the given R group be most likely to be found in the hydrophobic or hydrophilic region of a protein? A) hydrophobic B) both C) hydrophilic 11) Objective: 19.5 Global Outcomes: GO2 12) Objective: 19.5 Global Outcomes: GO2 13) -CH3 Objective: 19.5 Global Outcomes: GO2 14) – CH2CH2SCH3 Objective: 19.5 Global Outcomes: GO2 15) Objective: 19.5 Global Outcomes: GO2 16) Objective: 19.5 Global Outcomes: GO2 25 Copyright © 2013 Pearson Education, Inc. 17) Objective: 19.5 Global Outcomes: GO2 18) Objective: 19.5 Global Outcomes: GO2 19) Objective: 19.5 Global Outcomes: GO2 Answers: 11) A 12) C 13) A 14) A 15) C 16) C 17) C 18) A 19) A 26 Copyright © 2013 Pearson Education, Inc.