lecture 7

lecture 7 - Lecture 7 1/28/10 Background reading:...

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Lecture 7 1/28/10 Background reading: Outline: ± Hemoglobin ± Comparison of hemoglobin with myoglobin ± Conformational changes occur when hemoglobin binds to oxygen. ± Allosteric behavior of hemoglobin ± Hemoglobin as a blood buffer ± Bohr effect Garrett and Grisham: Chapter 6: Pages 194-201 Chapter 15: Bottom of Page 491- 500 Segel: Assignment: Segel: Read pages 86-90 Page 93: Problems 53, 54, and 55.
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± Hemoglobin Hemoglobin is an example of a protein with quaternary structure. It is a 68,000 molecular weight heteroteramer composed of two types of subunits: ( α and β ) Hemoglobin Contains 4 polypeptide chains: 2 α -chains (141 amino acids) 2 β -chains (146 amino acids) . A heme is bound to each chain. Hemoglobin has four oxygen binding sites per molecule. The tertiary structure of each chain of hemoglobin is similar to the structure of myoglobin. Myoglobin ± Comparison of hemoglobin with myoglobin
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Myoglobin and hemoglobin are both oxygen-binding proteins that appeared during the evolution of animals to land, when aerobic metabolic processes were no longer limited by the solubility of oxygen in water. Myoglobin is present as an oxygen storage protein in muscle, whereas hemoglobin is present in erythrocytes in the blood where it serves as an oxygen transport protein between the lungs and the body tissues. If study the binding property of myoglobin for oxygen, one gets a typical saturation curve. (Obeys Michaelis-Menten kinetics which Dr. Hilt will be lecturing on in the later part of this course.) As discussed in the last lecture, the heme group in the myoglobin is nestled in a pocket of the myoglobin and is the site of oxygen binding.
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If one compares the binding properties of myoglobin and hemoglobin for oxygen, there is a distinct difference. The binding curve of hemoglobin to oxygen is sigmoidal.
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the β -chains and H146 of the α -chains. Β 2 -chain carboxyl terminal end H146 α 1 -chain amino-terminal end α 2 -chain β 1 -chain amino-terminal end carboxyl terminal end K40 H146 K40 (Note a similar figure is shown on Page 489 of the Garrett textbook.) Deoxyhemoglobin has the carboxyl-terminal groups of all four chains anchored in salt linkages ± Conformational changes occur when hemoglobin binds to oxygen. X-ray crystallographic studies by Perutz showed that the deoxygenated and
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This note was uploaded on 06/23/2010 for the course BIS 102 taught by Professor Hilt during the Winter '08 term at UC Davis.

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lecture 7 - Lecture 7 1/28/10 Background reading:...

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