2.3 Study Guide Flashcards
Which is true about heme group structure?
a. It contains an iron atom in the ferric state
b. The iron makes three double bonds to the rest of the porphyrin ring
c. There are five total bonds made by the central iron atom
d. The ring structure is planar
e. None of the above
The ring structure is planar
What amino acid is most likely to coordinate the iron of a heme prosthetic group in a protein
a. His
b. Met
c. Ser
d. Tyr
e. Lys
Histidine (His)
Oxygen is non-polar and not readily diffusable in aqueous systems. Which strategy is used to assist
with oxygen diffusion?
a. Beta-barrel oxygen carrier proteins with hydrophobic interiors
b. Conversion to bicarbonate, which is soluble in aqueous solutions
c. Movement through porins
d. Heme-containing globin carrier proteins
Heme-containing globin carrier proteins
What is the function of His93 (His F8) in myoglobin?
a. To hydrogen bond with one of the oxygen atoms
b. To promote cooperativity
c. To bind the iron in the heme group
d. Both a and b
To bind the iron in the heme group
Which is TRUE about the hemoglobin T state
a. It has higher affinity for oxygen
b. It is the form that occurs when oxygen is bound
c. It is more stable in the absence of oxygen
d. The heme group is perfectly planar in T conformation
e. None of the above
It is more stable in the absence of oxygen
Order the steps of transition from hemoglobin T to R state
1. Ion pairs at the α1β2 interface shift
2. His F8 and the rest of the F helix shift in conformation
3. R state is achieved
4. Oxygen binding pulls the heme into a more planar conformation
a. 4, 2, 3, 1
b. 4, 3, 1, 2
c. 4, 1, 3, 2
d. 4, 2, 1, 3
e. 1, 2, 4, 3
4,2,1,3
Oxygen binding pulls the heme into a more planar conformation
His F8 and the rest of the F helix shift in conformation
Ion pairs at the α1β2 interface shift
R state is achieved
Why does carbon dioxide promote reversion of hemoglobin R state back to hemoglobin T state?
a. It causes steric hindrance of oxygen binding
b. It affects aspartate protonation
c. It binds to positively charged amino groups to to form a negatively charged functional group
d. All of the above
It binds to positively charged amino groups to to form a negatively charged functional group
The affinity of the tryptophan repressor for DNA increases after binding of tryptophan. What is this an
example of?
a. Negative cooperativity
b. A heterotropic allosteric effect
c. A homotropic allosteric effect
d. Tryptophan catabolism
A heterotropic allosteric effect
When graphing the number of occupied binding sites versus ligand concentration, which of the
following is TRUE about cooperative proteins?
a. The curve generated is hyperbolic
b. The curve generated is sigmoidal
c. The curve generated is linear
d. The curve indicates that only monomeric proteins can be cooperative
e. None of the above
The curve generated is sigmoidal
You are studying a receptor protein that acts as a dimeric complex, with each monomer binding a
separate ligand. You make a Hill plot reflecting the binding kinetics of your receptor and see that the
slope (nH or Hill coefficient) is one. What does this indicate about your receptor?
a. Ligand binding is non-cooperative
b. Ligand binding is positively cooperative
c. Ligand binding is negatively cooperative
d. Ligand binding occurs with high affinity
e. The ligand concentration for half maximal ligand binding
Ligand binding is non-cooperative
Which mutation of Glu6 causes sickle cell anemia?
a. Cys
b. Lys
c. Val
d. Gly
e. None of the above
Valine (Val)
Heme is broken down by our cells into less toxic intermediates. Which intermediate is made by the
enzyme heme oxygenase?
a. porphyrin
b. bilirubin
c. biliverdin
d. beta-hematin
e. hemozoin
biliverdin
Which is true about hemozoin?
a. It is produced through enzymatic degradation of heme
b. It is a large crystalline structure of up to 80,000 individual molecules
c. The production of hemozoin cause the green and yellow colors observable in bruises
d. It is produced by red blood cells to battle malarial parasites
e. None of the above
It is a large crystalline structure of up to 80,000 individual molecules
Why is chloroquinone an effective antimalarial drug?
a. It prevents P. falciparum from detoxifying heme
b. It binds to heme dimers to prevent assembly into hemozoin
c. It results in death of P. falciparum cells
d. All of the above
All of the above
