Chapter 5 Protein Function

Chapter 5 Protein Function Multiple Choice Questions 1. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 157 Difficulty: 2 Ans: D The interactions of ligands with proteins: A) are relatively nonspecific. B) are relatively rare in biological systems. C) are usually irreversible. D) are usually transient. E) usually result in the inactivation of the proteins. 2. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 158 Difficulty: 1 Ans: D A prosthetic group of a protein is a non-protein structure that is: A) a ligand of the protein. B) a part of the secondary structure of the protein. C) a substrate of the protein. D) permanently associated with the protein. E) transiently bound to the protein. 3. Reversible binding of a protein to a ligand: oxygen-binding proteins Pages: 158−159 Difficulty: 2 Ans: B When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by: A) one O atom and one amino acid atom. B) one O2 molecule and one amino acid atom. C) one O2 molecule and one heme atom. D) two O atoms. E) two O2 molecules. 4. Reversible binding of a protein to a ligand: oxygen-binding proteins Pages: 160−161 Difficulty: 2 Ans: A In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as: A) hyperbolic. B) linear with a negative slope. C) linear with a positive slope. D) random. E) sigmoidal. Downloaded by nimoh maurine () lOMoARcPSD| 52 Chapter 5 Protein Function 5. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 160 Difficulty: 2 Ans: E Which of the following statements about protein-ligand binding is correct? A) The Ka is equal to the concentration of ligand when all of the binding sites are occupied. B) The Ka is independent of such conditions as salt concentration and pH. C) The larger the Ka (association constant), the weaker the affinity. D) The larger the Ka, the faster is the binding. E) The larger the Ka, the smaller the Kd (dissociation constant). 6. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 163 Difficulty: 2 Ans: E Myoglobin and the subunits of hemoglobin have: A) no obvious structural relationship. B) very different primary and tertiary structures. C) very similar primary and tertiary structures. D) very similar primary structures, but different tertiary structures. E) very similar tertiary structures, but different primary structures. 7. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 165 Difficulty: 2 Ans: B An allosteric interaction between a ligand and a protein is one in which: A) binding of a molecule to a binding site affects binding of additional molecules to the same site. B) binding of a molecule to a binding site affects binding properties of another site on the protein. C) binding of the ligand to the protein is covalent. D) multiple molecules of the same ligand can bind to the same binding site. E) two different ligands can bind to the same binding site. 8. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 165 Difficulty: 1 Ans: C In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by: A) Fe2+ binding. B) heme binding. C) oxygen binding. D) subunit association. E) subunit dissociation. 9. Reversible binding of a protein to a ligand: oxygen-binding proteins Pages: 171−172 Difficulty: 2 Ans: C Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)? A) It binds at a distance from the heme groups of hemoglobin. B) It binds with lower affinity to fetal hemoglobin than to adult hemoglobin. C) It increases the affinity of hemoglobin for oxygen. D) It is an allosteric modulator. E) It is normally found associated with the hemoglobin extracted from red blood cells. Downloaded by nimoh maurine () lOMoARcPSD| Chapter 5 Protein Function 53 10. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 167 Difficulty: 2 Ans: C Which of the following is not correct concerning cooperative binding of a ligand to a protein? A) It is usually a form of allosteric interaction. B) It is usually associated with proteins with multiple subunits. C) It rarely occurs in enzymes. D) It results in a nonlinear Hill Plot. E) It results in a sigmoidal binding curve. 11. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 173 Difficulty: 1 Ans: D The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of ___________ interactions between molecules. A) covalent B) disulfide C) hydrogen bonding D) hydrophobic E) ionic 12. Reversible binding of a protein to a ligand: oxygen-binding proteins Page: 173 Difficulty: 2 Ans: C The fundamental cause of sickle-cell disease is a change in the structure of: A) blood. B) capillaries. C) hemoglobin. D) red cells. E) the heart. 13. Complementary interactions between proteins and ligands: the imm