Flashcards in Lecture 7 Deck (16)
What type of interactions stabilize the quarternary structures of hemoglobin and myoglobin?
Weak, non-covalent interactions
What are two functions of the hydrophobic interior of the Hemoglobin molecule?
Prevents oxidation of iron and allows reversible binding
What does cooperative binding mean when referring to the hemoglobin molecule?
Once one molecule of oxygen binds to hemoglobin, the next molecules of oxygen bind more easily (Same is true for the opposite, when removing oxygen)
What kind of effect is cooperative binding and why?
Allosteric Effect - relating to or denoting the alteration of the activity of a protein through the binding of an effector molecule at a specific site
Respectively, the oxygen binding curve of myoglobin and hemoglobin reflect what shapes?
Hyperbola and sigmoidal curves
What is the Bohr effect?
Hemoglobin's oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide. A pH decrease and CO2 concentration increase will cause hemoglobin proteins to release their bound oxygen
What is thalassemia?
Thalassemia is a blood disorder passed down through families (inherited) in which the body makes an abnormal form of hemoglobin, the protein in red blood cells that carries oxygen. The disorder results in excessive destruction of red blood cells, which leads to anemia.
What is Methemoglobinemia?
Methemoglobinemia is a blood disorder in which an abnormal amount of methemoglobin -- a form of hemoglobin -- is produced. Hemoglobin is the molecule in red blood cells that distributes oxygen to the body. Methemoglobin cannot bind or release oxygen.
What can iron bond to and how many bonds does it form in a heme molecule?
Iron can form six bonds: four with prophyrin nitrogens, plus two additional bonds, one above (bond to histidine) and one below the planar porphyrin ring (which can either be empty [DeoxyHb], bound to the oxygen molecule [OxyHb], or bound to water [MetHb])
What are major differences between Hemoglobin & Myoglobin?
Hemoglobin is found in RBCs, while Myoglobin is found in Muscle cells. Hemoglobin transports O2, while Myoglobin stores O2. Hemoglobin is a tetramer, while Myoglobin is a monomer
What is the Haldane effect?
Deoxygenation of the blood increases its ability to carry carbon dioxide. Therefore, whenever an oxygen molecule binds to hemoglobin, a CO2 molecule is released
What structural change occurs to iron in hemoglobin when it is deoxygenated?
Iron sits above the plane of the hemoglobin, rather than in the plane
How do salt bridges affect the structure of hemoglobin?
They allow for additional noncovalent interactions between subunits in deoxyhemoglobin, however these interactions are broken once deoxyhemoglobin becomes oxygenated to form oxyhemoglobin
What happens to hemoglobin oxygenation in the absence of 2,3-BPG?
Hemoglobin cannot bind to oxygen cooperatively in the absence of 2,3-BPG and acts like myoglobin
What effect on hemoglobin oxygenation does the presence of 2,3-BPG have? (What is the function of 2,3-BPG)
It causes hemoglobin to unload oxygen quicker and more readily