Oxygen disassociation curve.. Am I missing something in this video?

[phEight]

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Alright, check this video out... just forward to 4:40...

http://www.o2demand.com/acidbaseintroductionvideo

He is saying acidosis shifts the curve to the right, and that this increases the affinity for O2 on hemoglobin. I thought it was the opposite? A lower pH leads to a right shift which means less affinity for oxygen. I'm not sure if I'm missing something, the guy seems fairly confident about it lol

 

[Charles_Carmichael]

I haven't watched the video but I'm answering based on your description.

The shift to the right decreases affinity; it causes unloading of O2. The way I think about affinity is that a shift to the left makes the curve more hyperbolic and myoglobin (with a much higher affinity for O2 than hemoglobin) has a hyperbolic curve rather than sigmoidal; so, shift to the left = more hyperbolic = more myoglobin-like = more affinity. Hope this helps.

 

[phEight]

Thanks, that's also what I expected. Apparently that's not what this guy is saying... he is saying a right shift increases affinity for oxygen, which certainly doesn't seem to be true.

 

[thebillsfan]

Thanks, that's also what I expected. Apparently that's not what this guy is saying... he is saying a right shift increases affinity for oxygen, which certainly doesn't seem to be true.

if that's what he's saying, he's dead wrong. always a good thing to verify everything from at least two diff sources. even if somebody sounds authoritative, they could have just made a mental slip.

 

[minutemen11]

I haven't watched the video but I'm answering based on your description.

The shift to the right decreases affinity; it causes unloading of O2. The way I think about affinity is that a shift to the left makes the curve more hyperbolic and myoglobin (with a much higher affinity for O2 than hemoglobin) has a hyperbolic curve rather than sigmoidal; so, shift to the left = more hyperbolic = more myoglobin-like = more affinity. Hope this helps.

myoglobin has greater affinity to O2? I thought it was the other way around since myoglobin techincally has only 1 heme group as opposed to hemoglobin's 4. Each myoglobin binds 1 O2 molecule and each hemoglobin binds 4 O2 right?? I would think that myoglobin, which i know is the main type of hemoglobin in muscle cells, would have a lower affinity so that more O2 is released to the muscles.... Enlighten me haha..

also, as a quick review. hyperventilation causes shift to the left of the O2 curve.
increased temperature/ increased CO2/lower ph/ strenuous exercise shifts it to the right?

fetal hemoglobin has a greater affinity for O2, therefore shifting it to the left. the reason for this is because the fetus has lower 2,3-DPG correct? high concentrations of 2,3-DPG leads to lower O2 affinity.

sorry for the multitude of questions, im in panic mode, 7 days left before my mcat lol..

 

[Charles_Carmichael]

myoglobin has greater affinity to O2? I thought it was the other way around since myoglobin techincally has only 1 heme group as opposed to hemoglobin's 4. Each myoglobin binds 1 O2 molecule and each hemoglobin binds 4 O2 right?? I would think that myoglobin, which i know is the main type of hemoglobin in muscle cells, would have a lower affinity so that more O2 is released to the muscles.... Enlighten me haha..

also, as a quick review. hyperventilation causes shift to the left of the O2 curve.
increased temperature/ increased CO2/lower ph/ strenuous exercise shifts it to the right?

fetal hemoglobin has a greater affinity for O2, therefore shifting it to the left. the reason for this is because the fetus has lower 2,3-DPG correct? high concentrations of 2,3-DPG leads to lower O2 affinity.

sorry for the multitude of questions, im in panic mode, 7 days left before my mcat lol..

Myoglobin's oxygen dissociation curve is hyperbolic (http://www.colorado.edu/intphys/Class/IPHY3430-200/image/figure13g.jpg). It's designed to store O2 in muscle and works as a storage protein. If it had low affinity for O2, it wouldn't work well as a storage protein. While myoglobin is similar in structure/amino acid sequence to a hemoglobin subunit, it's not the exact same. Myoglobin stores O2 until there's a very low O2 condition in the cell (ie. during heavy exercise); then, it releases it's stored O2 for the muscle to use.

Yes, to all your shift questions.

fHb has higher affinity due to lower affinity of 2,3 DPG for fHb, not lower levels of 2,3 DPG.

Hope this helps.