Biochemistry Final

β-Lysine 82 in hemoglobin A is important for the binding of 2,3-BPG. in Hb Helsinki, this amino acid has been replaced by methionine. Which of the following should be true concerning Hb Helsinki?

It should have increased O2 affinity and, consequently, decreased delivery of O2 to tissues.

A 67-year-old man presented to the emergency department with a 1 week history of angina and shortness of breath. He complained that his face and extremities had a "blue color." His medical history included chronic stable angina treated with isosorbide dinitrate and nitroglycerin. Blood obtained for analysis was chocolate-colored. Which one of the following is the most likely diagnosis?

Methemoglobinemia

Given that the pI for glycine is 6.1, to which electrode, positive or negative, will glycine move in an electric field at pH 2? Explain?

Negative electrode. When the pH is less than the pI, the charge on glycine is positive because the α-amino group is fully protonated. (Recall that glycine has H as its R group).

Which one of the following statements concerning the binding of oxygen by hemoglobin is correct?

The oxygen affinity of hemoglobin increases as the percentage saturation increases.

A 70-year-old man was admitted to the emergency room with a 12-hour history of chest pain. Serum creatine kinase (CK) activity was measured at admission (day 1) and once daily. On day 2 after admission, he experienced cardiac arrhythmia, which was terminated by three cycles of electric cardioconversion, the latter two at maximum energy. [Note: Cardioconversion is performed by placing two paddles, 12 cm in diameter, in firm contact with the chest wall and applying a short electric voltage.] Normal cardiac rhythm was reestablished. He had no recurrence of arrhythmia over the next several days. His chest pain subsided and he was released on day 10. Which one of the following is most consistent with the data presented?

The patient had damage to his skeletal muscle on day 2.

Which one of the following statements concerning the peptide shown below is correct? Gly-Cys-Glu-Ser-Asp-Arg-Cys

The peptide is able to form an internal disulfide bond.

Which one of the following statements is correct?

β-Bends often contain proline.

Which one of the following statements concerning the ability of acidosis to precipitate a crisis in sickle cell anemia is correct?

Acidosis decreases the solubility of Hb S.

ADH requires NAD+ for catalytic activity. In the reaction catalyzed by ADH, an alcohol is oxidized to an aldehyde as NAD+ is reduced to NADH and dissociates from the enzyme. The NAD+ is functioning as (an):

Coenzyme-cosubstrate.

Which one of the following statements concerning the hemoglobins is correct?

Fetal blood has a higher affinity for oxygen than does adult blood because Hb F has a decreased affinity for 2,3-BPG.

A peptide bond:

Has a partial double-bond character.

In cases of ethylene glycol poisoning and its characteristic metabolic acidosis, treatment involves correction of the acidosis, removal of any remaining ethylene glycol, and administration and an inhibitor of alcohol dehydrogenase (ADH, alcohol: NAD+ oxidoreductase), the enzyme that oxidizes ethylene glycol to the organic acids that cause the acidosis. Ethanol (grain alcohol) frequently is the inhibitor given to treat ethylene glycol poisoning; it works by competitively inhibiting ADH. As a competitive inhibitor, ethanol:

Increases apparent Km without affecting Vmax.

An 80-year-old man presented with impairment of higher intellectual function and alterations in mood and behavior. His family reported progressive disorientation and memory loss over the last 5 months. There is no family history of dementia. The patient was tentatively diagnosed with Alzheimer disease. Which one of the following best describes the disease?

It is associated with the deposition of neurotoxic amyloid peptide aggregates.

Which of the following statements about the digestion of lipids is correct?

Patients with cystic fibrosis have difficulties with digestion because their thickened pancreatic secretions are less able to reach the small intestine, the primary site of lipid digestion.

The flat part of a titration curve (for glycine)

Represents the region where the net charge on glycine is zero.

Which one of the following statements about the absorption of lipids from the intestine is correct?

The TAG carried by chylomicrons is degraded to free fatty acids and glycerol by lipoprotein lipase on the endothelial surface of capillaries in muscle and adipose primarily.

Which one of the following statements about protein structure is correct?

The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.