Revision in Proteins Lectures; 1-1, 1-2 and 1-3
1. Methemoglobinemia; chocolate blood cyanosis, is a condition characterized by higher
than normal levels of methemoglobin. In addition to chocolate brown colored blood,
clinical manifestations also include shortness of breath, cyanosis, palpitations,
confusion, headaches and dizziness. Which enzyme is most likely deficient in a
chocolate blood cyanosis patient?
A. Carbonic anhydrase
B. BPG mutase (synthetizes BPG)
C. Methemoglobin reductase*
D. Lysyl oxidase
2. A patient shows a bluish color in his skin and mucous membranes, which is most likely
explained by which of the following?
A. Abnormally high BPG levels in his blood
B. A Glu to Val mutation in the beta chain of Hb
C. Increased oxidation of heme iron (Fe 2+) to the (Fe +3) state*
D. Decrease Hb affinity for O2
3. A young African American male was brought to the ER due to severe pain throughout
his body that started after vigorous exercise. An analysis of his blood shows reduced
red blood cell (RBC) count and "sausage-shaped" RBCs, rather than having the normal
concave shape. Which of the following would explain this observation?
A. Increased Hb oxygen binding capacity
B. Loss of quaternary structure
C. Increased hydrophobic interactions among Hb molecules in the T state*
D. Increased solubility oh Hb molecules in their T state
4. A young African American male was brought to the ER due to severe pain throughout
his body that started after vigorous exercise. An analysis of his blood shows reduced
red blood cell (RBC) count and "sausage-shaped" RBCs, rather than having the normal
concave shape. What would be the probable diagnosis for this patient?
A. Beta thalassemia
B. Alpha thalassemia
C. Helsinsky Hb
D. Sickle cell anemia*
5. Heme is the binding pocket of myoglobin and hemoglobin and is composed of:
A. negatively charged residues
B. polar residues
C. hydrophobic residues*
D. positively charged residues
1
6. ........................is a marker of muscle disease and myocardial damage.
A. Myoglobin*
B. Methionine
C. Hemoglobin
D. Glutamine
7. One of the following amino acids is considered an essential amino acid:
A. Alanine
B. Methionine*
C. Cysteine
D. Proline
8. Which one of the following statements concerning the hemoglobins is correct?
A. HbA is the most abundant hemoglobin in normal adults*
B. Fetal blood has a lower affinity for oxygen than does adult blood because HbF has an
increased affinity for 2,3-bisphosphoglycerate
C. The globin chain composition of HbF is α2δ2
D. HbA1c differs from HbA by a single, genetically determined amino acid substitution
9. Which one of the following statements concerning the binding of oxygen by hemoglobin
is correct?
A. The Bohr effect results in a lower affinity for oxygen at higher pH values
B. Carbon dioxide increases the oxygen affinity of hemoglobin by binding to the Cterminal groups of the polypeptide chains
C. The oxygen affinity of hemoglobin increases as the percentage saturation increases*
D. Oxyhemoglobin and deoxyhemoglobin have the same affinity for protons
10. 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 brown colored. Which one
of the following is the most likely diagnosis?
A. Hemoglobin SC disease
B. Methemoglobinemia*
C. Sickle cell anemia
D. β-Thalassemia
11. …………….. can bind only one molecule of O2, in contrast, ……………….. can bind four O2
molecules.
A. Myoglobin- hemoglobin*
B. Collagen- albumin
C. Hemoglobin-myoglobin
2
D. Elastin- fibrillin
12. Amino acid polypeptide chains fold into shapes that resemble spheres are called
globular proteins. This type of folding……………….solubility of proteins in water so
that………… groups on the protein’s surface and…………….groups in the interior.
A. decreases-hydrophobic-polar
B. increases- polar – hydrophobic*
C. increases- hydrophobic- polar
D. decreases-polar-hydrophobic
13. The distinctive arrangement of eight………………in myoglobin is found in all globins and
is called the globin fold.
A. β-pleated sheets
B. β-loops
C.  helices*
D.  turn β-helices
14. Based on motif analysis of many proteins, it now is clear that protein……………structure
is more reliably conserved than its amino acid sequence.
A. primary
B. quaternary
C. secondary
D. tertiary*
15. Hemoglobin contains two dimers of α β subunits held together by:
A. strong ionic and hydrogen bonds
B. strong hydrophobic interactions
C. covalent interactions
D. weak ionic and hydrogen bonds *
16. One of the followings is not true regarding fetal hemoglobin (HbF):
A. Major hemoglobin found in the fetus and newborn
B. It transfers O2 from maternal to fetal circulation across placenta
C. It is a tetramer with two  and two  chains
D. It has lower affinity for O2 than HbA*
17. What is the Met-Hb?
A. It forms due to high sulfur levels in blood (irreversible reaction)
B. It contains oxidized Fe 3+ (~2%) that cannot carry O2 *
C. It can carry O2 as usual hemoglobin
D. CO replaces O2 and binds 200X tighter than O2
3
18. An individual is in Mexico City at an altitude of 7,350 feet. He is having trouble breathing
with insufficient O2 being delivered to his tissues by Hb. Which treatment could
alleviate his condition?
A. A drug that induces metabolic alkalosis
B. A drug that increases 2,3-BPG production*
C. Start hyperventilating
D. Hydroxyurea (induces gamma chain synthesis)
19. A family has been using a propane heater in an enclosed apartment during winter. One
morning, a family member was difficult to awake and complained of a strong headache
and being tired. His mucous membranes are cherry red color. These symptoms are the
result of the following:
A. Decreased O2 delivery to tissues*
B. Increased blood flow to the brain
C. Decreased blood flow to the brain
D. Decreased O2 affinity to Hb
20. …………is the most common and stable conformation for a polypeptide chain.
A. α-helix*
B. β-pleated sheet
C. Random coil
D. Loop shape
21. All the following proteins have quaternary structures except:
A. Hemoglobin
B. Immunoglobulin G
C. Creatine Kinase
D. Myoglobin*
22. Level of structure found in hemoglobin but not in myoglobin:
A. Quaternary*
B. Primary
C. Secondary
D. Tertiary
23. Secondary structure in protein refers to:
A. Linear sequence of amino acids joined together by peptide bond
B. Regular folding of regions of the polypeptide chain*
C. Three-dimensional arrangement of all amino acids in polypeptide chain
D. Protein made up of more than one polypeptide chain
4
24. What type of covalent bonds link the amino acids in a protein?
A. Peptide bonds*
B. Hydrogen bonds
C. Ionic bonds
D. Glycosidic bonds
25. …………………is considered a quantitative hemoglobinopathy
A. hemoglobin C disease
B. hemoglobin SC disease
C. α-thalassemia*
D. Sickle cell anemia
26. Hemoglobin A (HbA), the major hemoglobin in adults, is composed of four polypeptide
chains (two α chains and two β chains, α2β2) held together by:
A. noncovalent interactions*
B. covalent interactions
C. disulfide bridges
D. All of the above
27. The binding of an oxygen molecule at one heme group increases the oxygen affinity of
the remaining heme groups in the same Hb molecule, this is called…………………..
A. synergism
B. allosterism
C. conformation
D. cooperativity*
28. Fetal hemoglobin (HbF) binds 2,3-BPG less tightly than does HbA and has………….oxygen
affinity.
A. Lower
B. Higher*
C. equal
D. no
29. Hemoglobinopathies are disorders primarily caused either by production of a
structurally abnormal Hb molecule as in……………………..or synthesis of insufficient
quantities of normal Hb subunits as in the………….
A. thalassemias- sickle cell anemia
B. sulf hemoglobinemia- sickle cell anemia
C. hemoglobin C disease- thalassemias*
D. thalassemias- hemoglobin C disease
5
30. Most of the CO2 produced in metabolism is hydrated and transported as…………ion
however some CO2 is carried as…………..bound to the terminal amino groups of
hemoglobin (forming carbaminohemoglobin.
A. bicarbonate- carbamate*
B. carbamate- bicarbonate
C. carbamate- H+
D. H+- bicarbonate
6