Quiz 1

A major driving force for protein folding is the hydrophobic effect, in which hydrophobic amino acid side chains tend to cluster together, usually in the core of globular proteins. This occurs primarily due to which of the following? 0/1 (A) Increasing hydrogen bond formation (B) Increasing the entropy of water (C) Increasing disulfide bond formation (D) Minimizing van der Waals interactions (E) Reducing steric hindrance between amino acid side chains

(B) Increasing the entropy of water

An environmentalist attempted to live in a desolate forest for 6 months, but had to cut his experiment short when he began to suffer from bleeding gums, some teeth falling out, and red spots on the thighs and legs. This individual is suffering from an inability to properly synthesize which one of the following proteins? 1/1 (A) Myoglobin (B) Hemoglobin (c) Collagen (d) Insulin (E) Fibrillin

(c) Collagen

A 0.22 M solution of lactic acid (pKa 3.9) is found to contain 0.20 M in the dissociated form and 0.02 M undissociated. What is the pH of the solution?

4.9

The pK of acetic acid is 4.8. What is the approximate pH of an acetate solution containing0.2 M acetic acid and 2 M acetate ion? 1/1 a. 0.48 b. 4.8 c. 5.8 d. 6.8 e. 10.8

5.8

A 67-year-old woman with depression comes to the physician because of easy bruising and bleeding of her gums for the past 2 months. She has been living alone since the death of her husband 1 year ago. She appears thin and has temporal wasting bilaterally. Physical examination shows bruises on her lower legs, swollen gums, and petechiae on the hard palate. This patient's symptoms are most likely due to defective synthesis of a substance that is composed primarily of which of the following amino acids? 0/1 Arginine Proline Tyrosine Glycine Lysine Alanine

Glycine

An investigator is conducting a study on hematological factors that affect the affinity of hemoglobin for oxygen. An illustration of two graphs (A and B) that represent the affinity of hemoglobin for oxygen is shown. Which of the following best explains a shift from A to B 0/1 Increased body temperature Decreased serum 2,3-bisphosphoglycerate concentration Increased hemoglobin γ-chain synthesis Increased serum pH Decreased serum pCO2

Increased body temperature

A 2-year-old Caucasian girl presents with severe vomiting, dehydration, and fever. Initial blood studies show acidosis with a low bicarbonate and an anion gap (the sum of sodium plus potassium minus chloride plus bicarbonate is 40 and larger than the normal 12 ± 2). Preliminary results from the blood amino acid screen show two elevated amino acids, both with nonpolar side chains. A titration curve performed on one of the elevated species shows two ionizable groups with approximate pKs of 2 and 9.5. Which of the following pairs of elevated amino acids is most likely elevated? 0/1 a. Aspartic acid and glutamine b. Glutamic acid and threonine c. Histidine and valine d. Leucine and isoleucine e. Glutamine and isoleucine

Leucine and isoleucine

The oxygen carrier of muscle is the globular protein myoglobin. Which of the following amino acids is highly likely to be localized within the interior of the molecule? 1/1 a. Arginine b. Aspartic acid c. Glutamic acid d. Valine e. Lysine

Valine

A 25-year-old patient shows lowered appetite, increased urination, and thirst. The physician suspects diabetes mellitus and confirms elevated urine glucose and ketones. Which of the following blood values is most compatible with diabetic ketoacidosis? a. b. c. d. e.

a

Water, which constitutes 70% of body weight, may be said to be the "cell solvent." The property of water that most contributes to its ability to dissolve compounds is the 1/1 a. Strong covalent bond formed between water and salts b. Hydrogen bond formed between water and biochemical molecules c. Hydrophobic bond formed between water and long-chain fatty acids d. Absence of interacting forces e. Fact that the freezing point of water is much lower than body temperature

b. Hydrogen bond formed between water and biochemical molecules

Under normal conditions in blood, which of the following amino acid residues of albumin is neutral? 1/1 a. Arginine b. Aspartate c. Asparagine d. Glutamate e. Histidine

c. Asparagine

A child with speech delay is found to have a large, abnormal peak when blood amino acids are measured. The abnormal amino acid migrates towards the cathode, indicating a positively charged side group in addition to its carboxyl and amino groups. Which of the following amino acids is most probable? 1/1 a. Alanine b. Glycine c. Histidine d. Leucine e. Valine

c. Histidine

Which one of the following statements correctly describes transport of O2 by hemoglobin? 1/1 a. O2 binds to hemoglobin more easily than does CO b. The binding of O2 to hemoglobin causes a valence change in the iron of the heme moiety c. Each of the four heme moieties binds O2 independently - d. The plot of percentage of O2 bound versus O2 pressure is sigmoidal in shape e. Increased CO2 concentrations increase O2 affinity

d. The plot of percentage of O2 bound versus O2 pressure is sigmoidal in shape

Which of the hemoglobin designations below best describes the relationship of subunits in the quaternary structure of adult hemoglobin? 1/1 a. (α1-α2)(β1-β2) b. α1-α2-α3-α4 c. β-β-β-α d. (β1-β2-β3-α1) e. (α1-β1)-(α2-β2)

e. (α1-β1)-(α2-β2)

A drug contains one ionizable group, a weak base with a pKa of 9.0. The drug enters cells via free diffusion through the membrane in its uncharged form. This will occur most readily at which of the following pH values? 0/1 a. 3.5 b. 5.5 c. 7.0 d. 7.6 e. 9.2

e. 9.2