Practice Tests Questions 5-7 Harm

Front 1

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 the binding.
E) The larger the Ka, the smaller the Kd (dissociation constant).

Back 1

The larger the Ka, the smaller the Kd (dissociation constant).

Front 2

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.

Back 2

very similar tertiary structures, but different primary structures.

Front 3

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.

Back 3

binding of a molecule to a binding site affects binding properties of another site on the protein.

Front 4

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.

Back 4

Oxygen binding

Front 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.
E) It is normally found associated with the hemoglobin extracted from red blood cells.

Back 5

C) It increases the affinity of hemoglobin for oxygen.

Front 6

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.

Back 6

C) It rarely occurs in enzymes.

Front 7

Carbon monoxide (CO) is toxic to humans because:

A) it binds to myoglobin and causes it to denature.
B) it is rapidly converted to toxic CO2.
C) it binds to the globin portion of hemoglobin and prevents the binding of O2.
D) it binds to the Fe in hemoglobin and prevents the binding of O2.
E) it binds to the heme portion of hemoglobin and causes heme to unbind from hemoglobin.

Back 7

D) it binds to the Fe in hemoglobin and prevents the binding of O2.

Front 8

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

Back 8

D) hydrophobic

Front 9

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.

Back 9

C) hemoglobin.

Front 10

An individual molecular structure within an antigen to which an individual antibody binds is as a(n):

A) antigen.
B) epitope.
C) Fab region.
D) Fc region
E) MHC site.

Back 10

B) epitope.

Front 11

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
E) Variable domain

Back 11

B. FE