AP Biology Questions and Answers (Graded A)

AP Biology Questions and Answers (Graded A) A mutation in the gene coding, for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a non-polar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has a much lower activity than the normal enzyme does. Which of the following most likely explains how the amino acid substitution has resulted in decrease catalytic activity by the mutated enzyme? A. The substitution decreased the mass of the enzyme so that the mutated enzyme binds more weakly yo the substrate than the normal enzyme does. B. The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does C. The substitution caused many copied of the mutated enzyme to cluster together and compete for substrate to bind. D. The substitution caused the directionality of the enzyme to change such that the amino terminus of the normal enzyme has become the carboxyl terminus of the mutated enzyme B. The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does A typical bag of fertilizer contains high levels of nitrogen, phosphorus, and potassium but trace amounts of magnesium and calcium. Which of the following best matches the fertilizer component with the molecule in which it will be incorporated by organisms in the area? A. Nitrogen will be incorporated into nucleic acids B. Phosphorus will be incorporated into amino acids C. Potassium will be incorporated into lipids D. Magnesium will be incorporated into carbohydrates A. Nitrogen will be incorporated into nucleic acids Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrate monomers into polymers. Which of the following best explains the reactions of these enzymes? A. Amylase acids in the removal of a water molecule to break covalent bonds whereas glycogen synthase aids in the addition of a water molecule to form a covalent bonds. B. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds. C. Amylase aids in the addition of a water molecule to form covalent bonds whereas glycogen synthase aids in the removal of a water molecule to break covalent bonds. D. Amylase aids in the removal of a water molecule to form covalent bonds whereas glycogen synthase aids in the addition of a water molecule to break covalent bonds. B. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds. A researcher measured the temperature at which two different samples of double-stranded denature (separate into single strands). Sample denatured at a significantly lower temperature than sample did. Based on the data, the researcher claims that the in sample is composed of a higher percentage of guanine and cytosine than the in sample is. Which of the following best supports the researcher's claim? A. The bonds between guanine and cytosine are covalent bonds, which require more energy to disrupt than those between adenine and thymine. B. Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds between