Problem 53
Methanol and ethanol are oxidized by alcohol dehydrogenase. In methanol poisoning, ethanol is given intravenously to prevent the formation of formaldehyde that has toxic effects. a. Draw the condensed structural formulas of methanol and ethanol. b. Would ethanol compete for the active site or bind to a different site? c. Would ethanol be a competitive or noncompetitive inhibitor of methanol oxidation?
Problem 55
Is the enzyme described in each of the following statements a simple enzyme or one that requires a cofactor? a. requires vitamin \(\mathrm{B}_{1}\) (thiamine) b. needs \(\mathrm{Zn}^{2+}\) for catalytic activity c. its active form consists of two polypeptide chains
Problem 56
Is the enzyme described in each of the following statements a simple enzyme or one that requires a cofactor? a. requires vitamin \(\mathrm{B}_{2}\) (riboflavin) b. its active form is composed of 155 amino acids c. uses \(\mathrm{Cu}^{2+}\) during catalysis
Problem 57
Identify a vitamin that is a component of each of the following coenzymes: a. coenzyme \(\mathrm{A}\) b. tetrahydrofolate (THF) c. \(\mathrm{NAD}^{+}\)
Problem 58
Identify a vitamin that is a component of each of the following coenzymes: a. thiamine pyrophosphate b. FAD c. pyridoxal phosphate
Problem 59
Ethylene glycol \(\left(\mathrm{HO}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{OH}\right)\) is a major component of antifreeze. In the body, it is first converted to \(\mathrm{HOOC}-\mathrm{CHO}\) (oxoethanoic acid) and then to \(\mathrm{HOOC}-\mathrm{COOH}\) (oxalic acid), which is toxic. a. What class of enzyme catalyzes the reactions described? b. The treatment for the ingestion of ethylene glycol is an intravenous solution of ethanol. How might this help prevent toxic levels of oxalic acid in the body?
Problem 60
Adults who are lactose intolerant cannot break down the disaccharide in milk products. To help digest dairy food, a product known as Lactaid can be added to milk and the milk then refrigerated for 24 hours. a. What enzyme is present in Lactaid, and what is the major class? b. What might happen to the enzyme if the Lactaid were stored at \(55^{\circ} \mathrm{C}\) ?
Problem 62
Fresh pineapple contains the enzyme bromelain that hydrolyzes peptide bonds in proteins. a. The directions for a gelatin dessert say not to add fresh pineapple. However, canned pineapple where pineapple is heated to high temperatures can be added. Why? b. Fresh pineapple is used in a marinade to tenderize tough meat. Why? c. What structural level of a protein does the bromelain enzyme destroy?
Problem 71
What are some differences between the following pairs? a. secondary and tertiary protein structures b. essential and nonessential amino acids c. polar and nonpolar amino acids d. dipeptides and tripeptides
Problem 72
What are some differences between the following pairs? a. an ionic bond (salt bridge) and a disulfide bond b. fibrous and globular proteins c. \(\alpha\) helix and \(\beta\) -pleated sheet d. tertiary and quaternary structures of proteins
