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Multiple Choice Questions on Protein Function

1. The interactions of ligands with proteins:
Biology Multiple Choice


a) usually result in the inactivation of the proteins.
b) are relatively rare in biological systems.
c) are usually irreversible.
d) are usually transient.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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

7. An individual molecular structure within an antigen to which an individual antibody binds is as an:
a) antigen.
b) epitope.
c) Fab region.
d) Fc region

8. Which of the following parts of the IgG molecule are not involved in binding to an antigen?
a) Fab
b) Fc
c) Heavy chain
d) Light chain

9. Which of the following generalizations concerning motor proteins is correct?
a) They convert chemical energy into kinetic energy.
b) They convert chemical energy into potential energy.
c) They convert kinetic energy into chemical energy.
d) They convert kinetic energy into rotational energy.

10. The energy that is released by the hydrolysis of ATP by actin is used for:
a) actin filament assembly.
b) actin filament disassembly.
c) actin-myosin assembly.
d) actin-myosin disassembly.

Learn more:
Books to Refer: Lehninger Principle of Biochemistry (Chapter 5 Protein Function)
Answers:
1. d) are usually transient.
2. b) one O2 molecule and one amino acid atom.
3. d) The larger the Ka, the faster is the binding.
4. b) binding of a molecule to a binding site affects binding properties of another site on the protein.
5. c) It increases the affinity of hemoglobin for oxygen.
6. d) hydrophobic
7. b) epitope.
8. b) Fc
9. a) They convert chemical energy into kinetic energy.
10. a) actin filament assembly.

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