MCB 450 Exam 1 Form A Key PDF - February 8, 2024

NAME:_____________________________ NETWORK ID:__________________ MCB 450 Exam 1 February 8, 2024 FORM A KEY...

NAME:_____________________________ NETWORK ID:__________________ MCB 450 Exam 1 February 8, 2024 FORM A KEY This exam consists of 50 questions for a total of 150 points. Choose the BEST answer from the available choices. 1) Which of the following biological molecules are highly versatile? a. Carbohydrates b. Lipids c. Nucleic acids d. Proteins e. Water 2) Which of the following enzyme is responsible for the formation of peptide bonds in proteins? a. acyltransferase b. DNA or RNA polymerase c. glycogen synthase d. Lipase e. peptidyltransferase 3) Hydrogen bonds mostly occur between hydrogen and which other atoms? a. Oxygen and nitrogen b. Sodium and magnesium c. Scandium and vanadium d. Silicon and Germanium e. Neon, argon, and xenon 4) Which of the following is an amphipathic molecule? a. Water b. Glucose c. NaCl (sodium chloride) d. Bile acid e. Ethanol 1 5) Which of the following is necessarily characterized by a non-covalent linkage? a. Peptide bond b. Ionic bond c. Phosphodiester bond d. Ester bond e. Glycosidic bond 6) Which of the following processes is powered by a hydrophobic interaction? a. Binding of enzymes to its substrates b. Membrane formation c. Binding of antibodies to antigens d. Dissolving of salt in water e. Dissolving of alcohols in water 7) What is the concentration of a NaOH solution with a pH of 12.7? a. 0.01M b. 0.05 M c. 0.1M d. 0.5M e. 1M 8) The pH of a buffered solution is 4.97. What is the approximate ratio of the concentration of acid to conjugate base if the pKa of the acid is 3.97? a. 1:10 b. 10:1 c. 100:1 d. 1:100 e. 1:1 9) What accounts for peptide bond planarity within a polypeptide? a. Electronegativity differences between nitrogen and carbon. b. Hydrogen bonding between amino acid side chains and water. c. Partial double bond character of the peptide bond. d. The peptide bond is not planar; it can actually rotate relatively freely. e. The fully double bonded peptide bond. 10) Which of the following are hydrophobic molecules? a. Charged molecules b. Molecules with two amino acids c. Polar molecules d. Nonpolar molecules e. Ionic molecules 2 11) Proline is called “alpha-helix breaker” because of its a. branch-side chain, which interferes with the backbone of the preceding turn. b. bulky side chain, which interferes with the backbone of the preceding turn. c. nitrogen atom in the peptide linkage has no hydrogen atom to participate in hydrogen bonds with other amino acids. d. charged side chain, which interferes with the backbone of the preceding turn. e. hydrophilic side chain, which interferes with the backbone of the preceding turn. 12) Which of the following interactions contributes to the secondary structure of a protein? a. Disulfide bonds between cysteine residues. b. Hydrogen bonds between R groups. c. Hydrophobic interactions. d. Peptide bonds between amino acids. e. Hydrogen bonds between amino groups and carbonyl groups of different amino acids. 13) _________ structure involves interactions between the various side chains of amino acids. a. Primary b. Secondary c. Tertiary d. Quaternary e. None of the above answers are true. 14) Which of the following type of bonds is involved in the tertiary structure of protein folding? a. Peptide bond b. Disulfide bond c. Phosphodiester bond d. Ester bond e. Glycosidic bond 15) When cooking an egg, opening the egg over a hot pan causes the non-yolk part of the egg to go from clear and viscous to white and solid. Adding heat to the egg white protein part of the egg is part of a process called what? a. Thermodynamics b. Hybridization c. Condensation d. Naturalization e. Denaturation 16) Which of the following is a protein-misfolding disease? a. Alzheimer's disease (AD) b. Gout c. Phenylketonuria d. Lesch-Nyhan syndrome e. Cystinuria 3 17) Listed below are some zymogens together with their putative activators. Select the pair that is incorrectly matched. a. Pepsinogen---activated by trypsin b. Trypsinogen---activated by enteropeptidase c. Chymotrypsinogen---activated by trypsin d. Proelastase---activated by trypsin e. Trypsinogen---trypsin 18) Hartnup disease results from the genetic defect in the transporter gene, SLC6A19, which is responsible for the absorption of which of the following amino acids? a. Cystine b. Glutamine c. Tryptophan d. Glycine e. Valine 19) Which of the following glycosidic bonds cannot be broken down by human digestive enzymes? a. a-1,4-Glycosidic bond in cellulose b. a-1,4-Glycosidic bond in maltose c. b-1,4 Glycosidic bond in lactose d. b-1,4 Glycosidic bond in cellulose e. a-1,b-2 Glycosidic bond in sucrose 20) Lactose intolerance is due to the deficiency of which of the following enzymes? a. maltase b. lactase c. sucrase d. cellulase e. a-amylase 21) Which of the following statements is NOT true regarding lipid digestion? a. Lipases break down the ester bonds in triacylglycerol. b. The major site for lipid digestion is the small intestine. c. Lipid digestion starts in the mouth by lingual lipase. d. Lipid can only be digested in stomach and small intestine. e. Lipase is one of the many digestive enzymes in lipid digestion. 22) What is the major role of bile salts in lipid metabolism? a. They break down the ester bonds in fat. b. They are important for the transportation of lipid in the blood. c. They neutralize the pH of chyme from the stomach. d. They break up (emulsify) the fat globules into smaller hydrophilic coated droplets. e. They are a structure component of chylomicrons. 4 23) Which of the following is NOT true regarding micelles in the intestine? a. They are very small fat molecules that have been emulsified by bile acids. b. They are small spherical water soluble microdroplets. c. They are disc-shaped clusters of amphipathic lipids with their hydrophobic groups on the inside and their hydrophilic groups on the outside. d. They are important for lipid absorption. e. They are transport vehicles after triglycerides and proteins bind during lipid digestion. 24) What is the function of ApoCII in mature chylomicrons? a. It is recognized by hepatic receptors for recycling. b. It is the structure protein for the formation of chylomicrons. c. It is required for the transportation of chylomicrons in the blood. d. It is necessary for the activation of lipoprotein lipase in some tissues. e. It is involved in the re-synthesis of TAG in the small intestine. 25) Steatorrhea is the presence of excess fat in feces due to poor digestion and malabsorption. Which of the following defect or deficiency in a disorder is likely associated with steatorrhea? a. Brush border enzyme level b. Gastric motility c. Ileal motility d. Lack of bile acids e. Kidney stone 26) ALT (Alanine aminotransferase) and AST (aspartate aminotransferase) are abundant in liver and can be used as plasma markers for liver diseases. What is the major function of these enzymes in liver? a. Maintain the turnover of the urea cycle since both enzymes are involved in the urea cycle. b. Synthesize non-essential amino acids from keto acids. c. Transfer the amino groups of different amino acids to α-ketoglutarate. d. Link the urea cycle intermediate to the TCA cycle intermediate for translocation out of the mitochondria. e. They are directly involved in the oxidative deamination of amino acids. 27) Amino groups of amino acids can be used for the synthesis of other nitrogen-containing molecules. What is the source of the two nitrogens in urea? I. Glutamate II. Alanine III. Aspartate IV. NH3 a. I, II b. I, III c. II, III d. II, IV e. III, IV 5 28) A deficiency in which of the following enzymes would directly limit the ability of the body to fix and dispose of ammonia? a. Carbamoyl phosphate synthetase I (CPS-I) b. Carbamoyl phosphate synthetase II (CPS-II) c. Asparagine synthetase d. Urease e. Alanine aminotransferase 29) Which of the following statements is TRUE for the disposal of nitrogen in hibernating bears? a. Urea is synthesized in the small intestine rather than the liver for disposal. b. Nitrogen is converted to NH4+ in the blood of the hibernating bears. c. Urea from liver is transported to small intestine to be converted to NH4+ for reuse in amino acid synthesis. d. Bears do not dispose of any nitrogen since they sleep during the winter. e. Nitrogen is converted to ammonia which is released from the breath of the hibernating bears. 30) A patient with PKU (Phenylketonuria) should be put on a life-long diet restricting which of the following? a. Phenylalanine b. Branched-chain amino acids (leucine, valine, and isoleucine) c. Sulfur-containing amino acids (methionine and cysteine) d. Thiamine e. Methionine 31) Which of the following co-factor is involved in the synthesis of succinyl CoA from L- methylmalonyl CoA? a. Pyridoxal phosphate b. Vitamin C c. N5, N10-methylene-tetrahydrofolate d. Methylcobalamin e. Deoxyadenosylcobalamin 32) Which of the following reactions is an example of ammonia fixation? a. Glutamine is converted to glutamate by glutaminase. b. Glutamate is converted to alpha-ketoglutarate by glutamate dehydrogenase. c. Alpha-ketoglutarate is converted to glutamate by glutamate dehydrogenase. d. Nitrogen in the atmosphere is converted into ammonia by some microorganisms. e. Alanine is converted to pyruvate by alanine aminotransaminase (ALT). 6 33) What enzyme is deficient in Maple Syrup Urine Disease (MSUD)? a. cystathionine alpha-synthase b. methylmalonyl CoA mutase c. branch-chain alpha-keto acid dehydrogenase d. tyrosinase e. phenylalanine hydroxylase 34) Which of the following answers completes the sentence correctly? Guanosine is a a. purine base. b. purine nucleoside. c. pyrimidine base. d. pyrimidine nucleoside. e. nucleotide. 35) Mycophenolic acid is a drug used to prevent graft rejection by inhibiting an enzyme in de novo purine synthesis. What is the direct target of this drug? a. PRPP synthetase b. Glutamine phosphoribosyl amidotransferase c. IMP dehydrogenase d. Dihydrofolate reductase e. Ribonucleotide reductase 36) Lesch-Nyhan syndrome is caused by a. mutations in the HGPRT (Hypoxanthine-guanine phosphoribosyltransferase) gene. b. mutations in the xanthine oxidase gene. c. mutations in the adenosine deaminase gene. d. an infection of the kidney. e. respiratory failure. 37) Degradation of which of the following products leads to the production of uric acid during the digestive process? a. Purines b. Pyrimidines c. Vitamins d. Fatty acids e. Proteins 38) What is the carbon source for the carbamoyl phosphate in pyrimidine synthesis? a. Aspartate b. ATP c. CO2 d. Glutamine e. Glutamate 7 39) What is the direct target of 5-Fluorouracil, a drug widely used in chemotherapy in cancer? a. PRPP synthetase b. CPSII c. Dihydrofolate reductase d. Ribonucleotide reductase e. Thymidylate synthase 40) Urine FIGlu test could be an indicator of the deficiency of which of the following vitamin? a. Vitamin B6 b. Vitamin A c. Vitamin C d. Vitamin D e. Vitamin B12 41) Human dihydrofolate reductase can be effectively and specifically inhibited by the administration of: a. uridylate (dUMP) b. colchicine c. sulfonamide d. methotrexate e. 5-fluorouracil (5-FU) 42) N5, N10-methylene-THF is the first THF (tetrahydrofolate) derivative generated in cells in one carbon metabolism. Which of the following amino acid provides this methylene (-CH2-) group? a. Alanine b. Glycine c. Serine d. Methionine e. Histidine 43) What is the source of electrons entering complex II? a. NADH from the TCA cycle and glycolysis b. FADH2 from the TCA cycle c. NAD+ from conversion of pyruvate to lactate d. FAD from pyruvate dehydrogenase e. Water 44) In the electron transport chain, what are the pair of electron carriers in and out of complex III? a. NADHàQH2 b. FADH2àQH2 c. QH2àcytochrome C d. cytochrome Càoxygen e. NADHàFe-S clusters 8 45) There are 3 conformations of the beta subunit of ATP synthase, with each representing different state of this enzyme. Which conformation represents the active state of ATP synthase for the synthesis of ATP? a. O (open) form b. L (loose) form c. T (tight) form d. A (attach) form e. R (release) form 46) Many of the carriers in the electron transport chain are cytochromes. The central component of the cytochrome capable of redox reactions is __________. a. a copper atom b. a hydrogen atom c. oxygen gas d. water e. an iron atom 47) Why is oxygen necessary in aerobic cellular respiration? a. It is needed for glycolysis, which begins the process of respiration in cells. b. It is important in creating oxaloacetic acid in the Kreb's cycle. c. It provides the hydrogen nuclei needed to create a proton gradient in the intermembrane space. d. It is the final electron acceptor in the electron transport chain. e. It is needed to transport electrons from NADH to QH2. 48) Which of the following is an inhibitor of ATP synthase by binding to the carboxylate group of glutamate of the C subunit? a. rotenone b. antimycin A c. cyanide d. dicyclohexylcarbodiimide (DCC) e. 2,4-dinitrophenol (DNP) 49) Why cytosolic NADH might yield potentially less ATP than mitochondrial NADH? a. Cytosolic NADH always loses energy when transferring electrons. b. Once NADH enters the matrix from the cytosol, it becomes FADH2. c. Electron transfer from cytosol to matrix if using the glycerol 3-phosphate shuttle. d. There is an energy cost for bringing cytosolic NADH into the matrix. e. Electron transfer from cytosol to matrix if using the malate-aspartate shuttle. 9 50) The uncoupler 2,4-dinitrophenol (DNP) prevents ATP synthesis while allowing electron transport to proceed because a. DNP is capable of transporting protons across the membrane, dissipating the proton gradient. b. DNP prevents the buildup of a proton gradient by altering the electron transfer complexes such that they no longer pump protons. c. DNP binds to the ATP synthase and acts as an inhibitor of the enzyme. d. DNP transports protons out of the mitochondria after they are pumped out of the matrix. e. DNP inhibits complex I on the ETC to prevent electron transport. -END OF EXAM- 10