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30 Cards in this Set
- Front
- Back
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What are globins? |
A superfamily of proteins containing the globin fold which is composed of 6-8 alpha helices arranged in a characteristic HEME-enclosing structure. |
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What residue does heme interact with in Hb? |
Histidine F8 |
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Where is myoglobin found? |
In the muscle confined to the cells of the muscle. |
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Where is heme found? |
In the circulatory system. |
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How many Nitrogen interact with an Iron molecule in Mb? |
4 |
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What happens when a naked heme interacts with an oxygen molecule? |
A superoxide forms |
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Give the formula for a naked him interacting with oxygen |
heme(Fe2+) + O2 <-> heme(Fe2+)~O2 -> heme(Fe3+) + O2-1 (superoxide)
**Fe3+ is not capable of binding O2 anymore
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What is another name for heme(Fe3+) |
metmyoglobin or methemoglobin |
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What percentage of Myoglobin is helical?
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70-80% |
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What kind of relationship on a graph does Myoglobin/O2 exhibit? |
Linear Relationship with a rectangular hyperbola
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What does Y(fractional saturation) stand for |
# of sites occupied / # of sites |
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What is the definition of P50? |
P50 is the partial pressure of Oxygen (pO2) at which HALF of the binding sites are occupied. |
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What is the p50 for Myoglobin? |
3 torr |
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What kind of curve occurs with hemoglobin/O2 binding? |
Sigmoidal Curve |
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If the partial pressure in the room is 120 torr, why is there a partial pressure of only 100 torr in the alveoli? |
When you inhale air there is still residual air in the alveoli and it mixes with the inspired air which dilutes it to about 100 torr. |
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What is the p50 for Hemoglobin? |
26 torr |
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In general, what is positive coopertivity? |
For hemoglobin, the binding of one oxygen facilitates the binding of the second and so on. This can only occur when there is more than one subunit. |
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What is the hill equation? |
log (Y/1-y) = n(logpO2 - log P50)
n = Hill coefficient
nmax = #subunits |
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Besides being the Hill coefficient, what else does n tell you? |
n = 1 ; There is no cooperativity
n > 1 ; Positive Cooperativity
n < 1 ; Negative cooperativity
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Why can't we use myoglobin instead of hemoglobin to deliver oxygen to the tissues? |
Myoglobin does not exhibit effects of positive cooperativity so it wouldnt desaturate the oxygen quick enough.
Positive coop. is important because when unsaturating it will give up oxygen very easily around physiological partial pressures. |
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What kind of shift occurs when the pH of the system occurs? |
A "right shift" |
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Why does a right shift improve oxygen delivery? |
If observing the sigmoidal graph, the area over the curve is the amount of oxygen delivered. With a right shift the area is larger. |
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What factors induce a right shift? |
1. [H+] increase = pH decrease 2. [CO2] increase 3. 2,3-BPG increase 4. Temperature increase |
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Why does 2,3-BPG cause a right shift? |
2,3-BPG is a product of glycolysis. It is a small molecule that has 5 negative charges on it. |
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What is significant about hemoglobin-nitrite (NO2-) interactions? |
Deoxy Hb has a capability to generate nitric oxide from nitrite. In this way it acts sort of like an enzyme. (Grosscloses words) |
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What enzyme reduces Fe3+ in Hb? What about in Mb? |
methemoglobin reductase
metmyoglobin reductase |
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What are the vasoregulatory properties of NO? |
"VIPA"
1. Vasodilation 2. Inhibition of smooth muscle cell 3. Proliferation and migration 4. Antiplatelet effects. |
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Why arent sickle cell anemia symptoms present immediately after birth? |
B chain synthesis of Hb begins to spike after birth. It is in these chains where the mutation takes place. |
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What can cause neural cells to potentially make Hb? |
Hypoxic Stress
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What other types of globins do we now know exist? |
Cytoglobin and Neuroglobin |
