Bio question

[pbure9]

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Which of the following decreases the affinity of hemoglobin to oxygen?

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A. Increased pH
B. Decreased metabolites
C. Increased pCO
D. Decreased pH
E. Decreased temperature

The right answer is D, and I understand why. But why can't it be C. Doesn't hemoglobin have a higher affinity for CO than for O2, so wouldn't an increased partial pressure of CO decrease O2 affinity. Or is the wording just odd?
Thanks

 

[BiomajorPreDent]

This was confusing to me as well, but heres the thing

When the blood pH gets too low, its acidic, and the tisues need oxygen, so hemoglobin releases O2 into the tissues, thus its affinity for hemoglobin decreases

About the CO thing:

"Carbon monoxide has a significant affinity to the iron sites in hemoglobin, the principal oxygen-carrying compound in blood. The affinity between hemoglobin and carbon monoxide is about 230 times stronger than the affinity between hemoglobin and oxygen.

Hemoglobin is a tetramer with four oxygen binding sites, and binding of carbon monoxide at one of these sites also increases the oxygen affinity of the remaining 3 sites, which therefore causes hemoglobin to retain oxygen that would otherwise be delivered to the tissue.

Levels of oxygen available for tissue use are decreased. This situation is described as carbon monoxide shifting the oxygen dissociation curve to the left. Blood oxygen content is actually increased in the case of carbon monoxide poisoning; because all the oxygen is in the blood, none is being given to the tissues, and this causes tissue hypoxic injury."

http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning

I hope this helps 🙂

 

[pbure9]

Thanks man. Although the question still bugs me that hemoglobins O2 binding capacity is decreased in the presence of CO since they both kinda compete for the same binding sites. And from what I know, CO is preferred over O2.

 

[Sublimation]

Thanks man. Although the question still bugs me that hemoglobins O2 binding capacity is decreased in the presence of CO since they both kinda compete for the same binding sites. And from what I know, CO is preferred over O2.

Try thinking about CO as a competitive inhibitor. The Hemoglobin affinity for oxygen doesnt decrease its still the same. The only difference is that hemo has a lower KM for CO then for O2. soo it will bind it more readily. affinity has to do with the enzyme. the more of the substarte you have has nothing to do with the affinity of the enzymes binding site. Let me try clearing it up by puting it this way.

Say you have a container with CO and O2, with the hemo enzyme. And you can measure how much O2 and CO that is bound. Now since the enzyme has higher affinity for CO it will bind more CO then O2. Now say you increase the number of O2 by 10x. You will find that (hypothetically speaking) more O2 is bound then CO. The enzyme didnt change its affinity for O2, its just the mere fact that the enzyme will most probably encounter a O2 instead of a CO more frequently so it will bind it (this is how we deal with competative inhibitors) increase the concentration of the desired one.

On another note. Affinity has to do with the binding site. the binding site is very stereospecific. Remember with proteins FORM=Funtion. Now a shift in pH will change the conformation of the enzyme in a way to elicit a certain response. (remember pH can change the shape of an enzyme) The changed shape of this enzyme will alter its affinity. I kno im kinda all over the place with my explanation lol. I hope this helps.

 

[BTtheman777]

are bio questions this detailed on the real thing?

 

[Sublimation]

are bio questions this detailed on the real thing?

From wat i can see, its not detail, its application. But to be honest every question ive encountered so far ive seen in a diagram in the campbell book. (i have not taken the DAT yet) but from my practice tests and destroyer everything is in the Fig. i encountered.

 

[DoctaWalnuts]

From wat i can see, its not detail, its application. But to be honest every question ive encountered so far ive seen in a diagram in the campbell book. (i have not taken the DAT yet) but from my practice tests and destroyer everything is in the Fig. i encountered.

How are you scoring on the practice tests? You are probably doing really well. 👍

 

[Sublimation]

How are you scoring on the practice tests? You are probably doing really well. 👍

Im doin okay, not great. The problem with me is that i never took anatomy. And bio2 lol...wow man we had a stupid professor he used to post the test online before he gave it to us lol....everyone got an A+ he was leaving that summer lol so i dont know **** when it comes to plants taxonomy evolution and ecology lol. Ive only taken one upper level bio course, Cell Biology lol. So i dont have that edge alot of other juniors have. Hopefully ill do well.

 

[BiomajorPreDent]

Dont sweat it, the stuff you didnt learn in bio2, like animals and plants, you can learn in cliffs

and the systems which u didnt learn in physiology, you can learn from cliffs also, or by reading through them on campbells

make sure you read up genomics and DNA technology and cDNA stuff

developmental bio you didnt get either is also big

having taken upper level cell bio will help as well

 

[Sublimation]

Dont sweat it, the stuff you didnt learn in bio2, like animals and plants, you can learn in cliffs

and the systems which u didnt learn in physiology, you can learn from cliffs also, or by reading through them on campbells

make sure you read up genomics and DNA technology and cDNA stuff

developmental bio you didnt get either is also big

having taken upper level cell bio will help as well

i hate embryology lol. Anatomy i didnt mind at all. Thats all ive been doin for bio, alot of the bio 2 i didnt learn. al the other crap i kno pretty well.

 

[DoctaWalnuts]

Im doin okay, not great. The problem with me is that i never took anatomy. And bio2 lol...wow man we had a stupid professor he used to post the test online before he gave it to us lol....everyone got an A+ he was leaving that summer lol so i dont know **** when it comes to plants taxonomy evolution and ecology lol. Ive only taken one upper level bio course, Cell Biology lol. So i dont have that edge alot of other juniors have. Hopefully ill do well.

I bet you will do really well. No worries!