Hard question!

[stronghold]

---

Members don't see this ad.

Which of the following is the mechanism of right shift in Oxygen sat. curve in acidic environment?

1) Competition between oxygen and Lactate
2) Competition between oxygen and Chloride
3) Competition between oxygen and Ketone bodies
4) Transformation of oxygen from tetramer to a dimer


Why?

 

[Brain Bucket]

Which of the following is the mechanism of right shift in Oxygen sat. curve in acidic environment?

1) Competition between oxygen and Lactate
2) Competition between oxygen and Chloride
3) Competition between oxygen and Ketone bodies
4) Transformation of oxygen from tetramer to a dimer


Why?

Haven't done pulm, but best guess: Lactate - Bohr effect?

edit: What's the answer? Don't keep us in suspense.

 

[Anastomoses]

From PubMed:
Binding constants for both anions to deoxy and oxy Hb were estimated. Lact and Cl have comparable binding constants to deoxy hemoglobin. By contrast Lact binds to oxy hemoglobin to a lesser extent than Cl. This may account for the differences observed in the effects of Lact and Cl on the function of hemoglobin. The reason for the low affinity of oxy hemoglobin for Lact may be related to steric differences between the two anions.

 

[stronghold]

Haven't done pulm, but best guess: Lactate - Bohr effect?

edit: What's the answer? Don't keep us in suspense.

I don't know the answer man! I just got that question from an old note without key answers

From PubMed:
Binding constants for both anions to deoxy and oxy Hb were estimated. Lact and Cl have comparable binding constants to deoxy hemoglobin. By contrast Lact binds to oxy hemoglobin to a lesser extent than Cl. This may account for the differences observed in the effects of Lact and Cl on the function of hemoglobin. The reason for the low affinity of oxy hemoglobin for Lact may be related to steric differences between the two anions.

Thanks man. So you mean the answer is Lactate. May you explain more?

 

[Doctosanthewan]

I would have guessed lactate. My logic is that in exercise you get that right shift due to protons binding to Hb, causing Hb to have less affinity to oxygen --> right shift and oxygen is thus unloaded at the tissues to supply more oxygen to the exercising muscle. And since lactate is acidic its going to be releasing lots of protons... Anyway, that was my thought process, not sure if it's totally correct...??

 

[SOML]

I would have guessed lactate. My logic is that in exercise you get that right shift due to protons binding to Hb, causing Hb to have less affinity to oxygen --> right shift and oxygen is thus unloaded at the tissues to supply more oxygen to the exercising muscle. And since lactate is acidic its going to be releasing lots of protons... Anyway, that was my thought process, not sure if it's totally correct...??

Haven't done pulm, but best guess: Lactate - Bohr effect?

edit: What's the answer? Don't keep us in suspense.

Makes sense. And though not super credible, heeeeere's wikipedia! :

with increased acidity, the hemoglobin binds less O2 for a given PO2 (and more H+). This is known as the Bohr effect.

Also, don't need to know but random and interesting:

A reduction in the total binding capacity of hemoglobin to oxygen (i.e. shifting the curve down, not just to the right) due to reduced pH is called the root effect. The Root effect is to be distinguished from the Bohr effect where only the affinity to oxygen is reduced. Hemoglobins showing the root effect show a loss of cooperativity at low pH.This is seen in bony fish.

 

[Zedor]

My guess is chloride from the roc chloride shift in exchange for bicarbonate

http://www.jbc.org/content/255/12/5525.full.pdf

 

[Modeselektor]

lactate = lactic acid.

hemoglobin doesn't care where the H+ came from, whether its from freshly dissociating carbonic acid or lactate or you shoot someone up with HCl. The increased protons will cause the bohr effect.

 

[Anastomoses]

I don't know the answer man! I just got that question from an old note without key answers



Thanks man. So you mean the answer is Lactate. May you explain more?

Yes, the answer is lactate.

 

[Brain Bucket]

lactate = lactic acid.

hemoglobin doesn't care where the H+ came from, whether its from freshly dissociating carbonic acid or lactate or you shoot someone up with HCl. The increased protons will cause the bohr effect.

I don't think it's just the hydroniums; lactate also binds Hb and causes the Bohr effect. I don't know which one has a greater effect in this circumstance though.

 

[Shjanzey]

I don't think it's just the hydroniums; lactate also binds Hb and causes the Bohr effect. I don't know which one has a greater effect in this circumstance though.

Can you cite where lactate actually binds? Everything I read was related to H+ concentration, which makes more sense in the context of the question. Exercise would cause more lactic acid production, increasing the demand for O2 within the muscles. Lower pH would cause Bohr Effect and O2 should unbind.

On another note, I find the usage of the word "competition" within the answers to be very misleading. As I understand it the mechanism is due to allosterism and the T/R states of the heme. Not necessarily "competitive binding", however I do know that binding certain molecules (O2, CO2) helps shift the molecule from a T --> R state and vice-versa. In mind mind this isn't necessarily "competitive binding", but I could be wrong 😀

 

[Modeselektor]

I don't think it's just the hydroniums; lactate also binds Hb and causes the Bohr effect. I don't know which one has a greater effect in this circumstance though.

That's pretty cool but I'd figure the question is asking for a more basic mechanism.

The causes of shift to right can be remembered using the mnemonic, "CADET, face Right!" for CO2, Acid, 2,3-DPG, Exercise and Temperature

Either way we both end up at the same answer.

Ketone bodies is kinda confusing because they are also acidic.
Note: diabetics in ketoacidosis and their respiratory symptoms.

 

[Brain Bucket]

Can you cite where lactate actually binds?

I just remember it vaguely from Biochem. I'm sure you could find a paper that states it if you're interested. I could, of course, be wrong.

As I understand it the mechanism is due to allosterism

Yep. I long ago learned that biochemists dumb things down for us even if it's wrong. I no longer question their explanations because trying to truly understand orgo is a black hole which will take up your entire life. edit: Although, it's still classified as competitive inhibition, so technically, it's right.

That's pretty cool but I'd figure the question is asking for a more basic mechanism.

Agreed.

I also prefer that mnemonic over FA's. The A can also stand for Altitude (I think) or Anemia. The E could be Elevation if you prefer it over Altitude.