Protein Disease
In hemoglobin, Fe²⁺ must remain in the reduced state to bind oxygen. Which structural feature of the globin protein MOST directly helps maintain iron in the Fe²⁺ state?
A. The polarity of the α and β chain exterior
B. The hydrophobic heme pocket that limits exposure to oxidizing agents
C. The distal histidine forming a covalent bond to Fe²⁺
D. The porphyrin ring lowering the pKa of the heme group
B. The hydrophobic heme pocket that limits exposure to oxidizing agents
Which protein exports iron from cells?
A) Hepcidin
B) Ferroportin
C) Transferrin
D) Ferritin
B) Ferroportin
Why do the clinicians decide to test the patient’s urine for 8-oxodG?
A. 8-oxodG directly identifies which gene is mutated
B. It reflects ongoing oxidative DNA damage being repaired
C. It is a molecule released by polyps that have turned
D. It shows how effectively iron is transported by transferrin
B. It reflects ongoing oxidative DNA damage being repaired
Which statement best describes hemoglobin’s subunit structure?
A. One polypeptide chain with four heme groups
B. Two alpha and two beta chains, each containing one heme
C. Four identical beta chains
D. Two gamma and two delta chains in adults
B. Two alpha and two beta chains, each containing one heme
High transferrin saturation indicates:
A) Low serum iron
B) Iron-binding sites mostly filled
C) Excess hepcidin
D) Low ferritin
B) Iron-binding sites mostly filled
Iron participates in the Fenton reaction, generating hydroxyl radicals that can damage DNA. Which factor MOST directly enables iron to drive this reaction?
A. Its ability to cycle between Fe²⁺ and Fe³⁺
B. Its role in forming Fe–S clusters in repair enzymes
C. Its transport by transferrin in the bloodstream
D. Its storage inside ferritin to prevent oxidation
A. Its ability to cycle between Fe²⁺ and Fe³⁺
Why is Fe²⁺ essential for oxygen binding?
A. Fe²⁺ repels oxygen so it can diffuse faster
B. Fe²⁺ covalently binds oxygen
C. Fe²⁺ keeps the heme ring from unfolding
D. Fe²⁺ forms a coordinate bond with oxygen
D. Fe²⁺ forms a coordinate bond with O₂
High transferrin saturation indicates:
A) Low serum iron
B) Iron-binding sites mostly filled
C) Excess hepcidin
D) Low ferritin
B) Iron-binding sites mostly filled
Dr. 3 and Dr. House explained that guanine is the most easily oxidized of the four DNA bases. What property mentioned of guanine BEST explains why guanine is so susceptible?
A. It has the lowest ionization potential out of the four nitrogenous bases
B. It has fewer hydrogen-bond donors than other bases
C. Guanine has the ability to bond to both cytosine and adenine because it has many hydrogen bonds
D. It is replaced most frequently during replication
A. It has the lowest ionization potential out of the four nitrogenous bases
The term for iron that is not tightly bound to proteins is:
A) Ferritin
B) Transferrin
C) Labile iron
D) Hemosiderin
C) Labile iron
This molecule, produced by active muscle cells, binds to the terminal amine groups of hemoglobin chains, pulling the prosthetic group upward and decreasing iron–oxygen orbital overlap—thereby promoting oxygen unloading.
Options:
A. Lactic acid
B. Carbon dioxide
C. Nitric oxide
D. Fe²⁺
B. Carbon dioxide
Why does the patient develop diabetes in ferroportin overload?
A) Iron damages pancreatic beta cells
B) Insulin is overproduced
C) JNK is inhibited
D) Trx is overactive
A) Iron damages pancreatic beta cells
OGG1 is one of the enzymes that prevents oxidative DNA lesions from accumulating. What is OGG1’s PRIMARY role in maintaining genomic stability?
A. Removing the adenine that mispairs with 8-oxo-G during replication
B. Recognizing and excising 8-oxo-guanine directly from DNA
C. Creating the iron-sulfur clusters needed for MUTYH to remove adenine mispaired with 8-oxo-G
D. Converting 8-oxo-G back into normal guanine
B. Recognizing and excising 8-oxo-guanine directly from DNA