Chapter 7 Review Questions

 

1. One theory of amyloid fibril formation is that sections of α-helical structure are converted to β-sheets. Such regions of the amyloid proteins would most likely lack which one of the following amino acids?

Proline

2. In order for lipid-based hormones such as testosterone or estrogen to be transported in the bloodstream, they are bound to and transported by water-soluble proteins. In order to be water-soluble, the transporting protein contains which one of the following amino acids on its surface in contact with aqueous blood?

Arginine

3. A patient has wheezing and shortness of breath, which are his typical asthma symptoms, so he takes a “rescue inhalant,” which is a β₂-adrenergic receptor agonist. The active ingredient of the inhalant relaxes the smooth muscle of the bronchi and allows him to breathe more normally. The receptor to which the agonist binds can be best described by which one of the following?

A transmembrane protein

4. Autopsies of patients with Alzheimer disease show protein aggregates called neurofibrillary tangles and neuritic plaques in various regions of the brain. These plaques exhibit the characteristic staining of amyloid. Which of the following structural features is the most likely characteristic of at least one protein in these plaques?

A high content of β-pleated sheet structure

5. While studying a novel pathway in a remote species of bacteria, you discover a new globular protein that phosphorylates a substrate, using ATP as the phosphate donor. This protein most likely contains which one of the following structures?

An actin fold

 

6. β₂-Adrenergic agonists used as treatments for acute asthmatic attacks were formulated to have a higher affinity for the β₂-adrenergic receptor than epinephrine. Which one of the following would be true of the β₂-agonist as compared to epinephrine?

The K _a of the agonist is higher than that of adrenaline.

7. A patient is exposed to hepatitis A and as a preventative measure is given hepatitis A immune globulin to prevent the patient from contracting the disease. The vaccine is an IgG immunoglobulin specific for coat proteins of the hepatitis A virus. The target of the immunoglobulin binds to which of the following locations in the immunoglobulin? Choose the one best answer.

A site consisting of variable regions of both the light and heavy chains

8. Each IgG molecule (like hepatitis A immunoglobulin) contains two light and two heavy chains, which can be separated by the loss of which one of the following types of interactions?

Disulfide bonds

 

9. A patient with type 1 diabetes was able to lower her HbA1c value from 8.2% to 5.9%. This occurred because of a reduction of which one of the following processes?

Nonenzymatic glycation

 

10. In amyloidosis, α-helices may form alternative β-sheets of amyloid fibrils. The α-helices in these proteins can be characterized by which one of the following?

They are formed principally by hydrogen bonds between a carbonyl oxygen atom in one peptide bond and the amide hydrogen from a different peptide bond.

11. The classic experiment to demonstrate that primary structure determines secondary and tertiary structure, as well as overall protein folding, was performed by Anfinsen and colleagues in 1973. In this experiment, the enzyme ribonuclease was denatured such that the protein lost all enzymatic activity, and then renatured, at which point it was shown that the protein recovered its enzymatic activity. Such an experiment would have failed if mature insulin were selected as the protein to denature due to which one of the following?

The primary structure of insulin has been altered after initial protein folding.

 

14. The forces responsible for initiating and maintaining secondary and tertiary structures have which one of the following in common?

Hydrogen bonds

15. Consider a single subunit globular protein that binds a ligand with a K _d of 10^{− 6} M in its native state. However, in response to a certain extracellular signal, two serine residues on the protein become phosphorylated, and the phosphorylated protein now binds the ligand with a K _d of 10^{− 9} M. Such a change in binding affinity can occur due to which one of the following?

The tertiary structure is altered because of the ability to now form ionic interactions.