Exam 3 Key

Exam 3 Key - Name_ CHEM 431/531 - Biochemistry I/Exam...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Name__________________________________________ CHEM 431/531 - Biochemistry I/Exam III/November 06, 2006 Part I: Hemoglobin and Cooperativity - Answer ONLY 4 out of the 8 questions. 1. Why is it advantageous for hemoglobin to have allosteric properties? Hemoglobin binds oxygen in a positive cooperative manner. This allows it to become saturated in the lungs, where oxygen pressure is high. When the hemoglobin moves to tissues, the lower oxygen pressure induces it to release oxygen and thus deliver oxygen where it is needed. 2. Explain the structural differences between fetal hemoglobin and adult hemoglobin. Explain how fetal hemoglobin can bind oxygen released by adult hemoglobin inside the uterus. This must include a discussion of 2,3 BPG as part of your answer. Fetal hemoglobin contains two α and two γ chains, in contrast to adult hemoglobin with two and two β chains. The fetal hemoglobin chain is probably a result of gene duplication and divergence. The difference in the chains results in a lower binding affinity of 2-3 BPG to fetal hemoglobin. Thus, the fetal hemoglobin has a higher affinity for oxygen, and the oxygen is effectively transferred from the mother’s hemoglobin to fetal hemoglobin. 3. Describe the octahedral coordination sphere of the iron ion in hemoglobin and myoglobin. The Fe +2 ion is coordinated to the four nitrogens in the center of the protoporphyrin of the heme. The fifth coordination site is occupied by the “proximal histidine” of the globin chain. The oxygen is bound to the sixth coordination site of the iron. 4. Briefly describe the cause of sickle-cell anemia. Sickle-cell anemia is a genetic disorder that is the result of a single substitution of β6 Glu with a Val. This changes a negatively charged side chain to a nonpolar, hydrophobic side chain. This Val binds into a hydrophobic pocket on the β chain of an adjacent molecule whose β6 Val binds to another molecule, thus hemoglobin aggregates. These aggregates form long fibers that strain the RBC and force into a sickled shape. The distorted red blood cells clog capillaries and impair blood flow, resulting in the sickle-cell crisis. The sickled cells are then destroyed, resulting in the anemia . 5.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/05/2011 for the course BLY 440 taught by Professor Williams during the Fall '10 term at Alabama.

Page1 / 5

Exam 3 Key - Name_ CHEM 431/531 - Biochemistry I/Exam...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online