Biochemistry Module 3 Final Exam 2025

T/F: The amino acids lysine and arginine both contain sulfur atoms. - -False *only cysteine and methionine contain sulfur T/F: The amino acids serine and methionine both contain sulfur atoms. - -False *serine does not, but methionine does T/F: The following secondary structure shown below is an example of a beta-turn. - False T/F: The side chain of histidine is bonded to the backbone nitrogen atom. - -False *proline, not histidine T/F: The side chain of proline is bonded to the backbone nitrogen atom. - -True T/F: The name of the molecule that binds to an enzyme is called the apoenzyme. - False *substrate, not apoenzyme T/F: The name of the molecule that binds to an enzyme is called the ligand. - -False *substrate, not ligand T/F: An inhibitor that binds at the active site is an uncompetitive inhibitor. - -False *competitive inhibitor, not an uncompetitive inhibitor T/F: An inhibitor that binds at the active site is a coenzyme. - -False *competitive inhibitor, not a coenzyme Which amino acids differ by only one atom? A) Ser and Thr B) Leu and Ile C) Ala and Ser D) Asp and Asn E) Ser and Cys - -E) Ser and Cys Biochemistry Biochemistry *serine has an -OH group where cysteine has an -SH group Which amino acids both have an R group (side chain) with an -OH functional group? A) Ser and Thr B) Leu and Ile C) Ala and Ser D) Asp and Asn E) Ser and Cys - -A) Ser and Thr The formation of a peptide bond between two amino acids is an example of a(n) ______________ reaction. A) Cleavage B) Condensation C) Group transfer D) Isomerization E) Oxidation reduction - -B) Condensation The peptide Ala-Glu-Gly-Ala-Leu has ___. A) A disulfide bond B) 5 peptide bonds C) 4 peptide bonds D) A proline residue E) No C-terminal - -C) 4 peptide bonds Formally, when there are 100 or more amino acids that are covalently linked together, it is called a ___. A) Polypeptide B) Oligopeptide C) Peptide D) Protein E) Polyprotein - -D) Protein *protein = 100-200 amino acids oligopeptide = 2-20 amino acids polypeptide = 99 amino acids peptide = no limit What unit is used by biochemists to indicate the mass of a protein? A) g/mol B) Da Biochemistry Biochemistry C) Ba D) Mol/g E) g - -B) Da All of the 20 standard amino acids contain an R-group that is attached to the: A) α carbon B) Carboxyl group C) Amino group D) β carbon E) None of the above - -A) α carbon Which of the following correctly matches the amino acid with its one letter abbreviation? A) Tyrosine, T B) Lysine, L C) Phenylalanine, P D) Aspartic acid, D E) Proline, R - -D) Aspartic acid, D Which of the following correctly matches the amino acid with its one letter abbreviation? A) Tyrosine, T B) Glutamic acid, E C) Phenylalanine, P D) Aspartic acid, A E) Proline, R - -B) Glutamic acid, E By convention, polypeptides are read in which order? A) N to C-terminus B) C to N-terminus C) 5' to 3' D) 3' to 5' E) Smallest to largest amino acid by weight - -A) N to C-terminus Roughly how amino acids are there in one turn of an alpha helix? A) 1 B) 2.8 C) 3.6 D) 4.2 E) 10 - -C) 3.6 In an alpha helix, the R groups on the amino acid residues: Biochemistry Biochemistry A) Alternate between the outside and inside of the helix B) Are found on the outside of the helix spiral C) Cause only right-handed helices to form D) Generate the hydrogen bonds that form the helix E) Stack within the interior of the helix - -B) Are found on the outside of the helix spiral Motifs are classified primarily by their ___. A) Amino acid sequence B) Evolutionary relationships C) Function D) Secondary structure content and arrangement E) Subunit content and arrangement - -D) Secondary structure content and arrangement The secondary structure show below is an example of a(n): - -antiparallel beta sheet The overall three-dimensional shape of a single-folded polypeptide is ___ structure. A) secondary B) tertiary C) quaternary D) quasi E) motif - -B) tertiary How many classes of enzymes are recognized by the IUBMB? A) 3 B) 4 C) 5 D) 6 E) 7 - -D) 6 An enzyme requires Cr3+ for catalysis. When the enzyme contains the Cr3+ is called: A) holoenzyme B) apoenzyme C) fully ready molecule D) inhibitor E) competitive inhibitor - -A) holoenzyme *enzyme without cofactor = apoenzyme, enzyme with cofactor = holoenzyme When a substrate has just started its conversion to a new molecule, it is said to be in the ___. Biochemistry Biochemistry Biochemistry A) stable mode B) unstable mode C) transition state D) conversion state E) conversion mode - -C) transition state Which of the following would change the rate of an enzyme-catalyzed reaction? A) amino acids, concentration, and temperature B) pH, concentration, and temperature C) pH, polarity, and concentration D) polarity, concentration, and temperature E) pH, polarity, and temperature - -B) pH, concentration, and temperature Which of the following described induced fit? A) When a substrate bind to an enzyme, the enzyme induces loss o