kab55 asked in Science & MathematicsMedicine · 1 decade ago

hemoglobin buffer system?

i'm a confused about this hemoglobin buffer system.. sorry if this is going to be a little long! i think i'm mainly confused about the basics..

i know that this system uses chloride shifts to maintain acid-base balance.

but when they say "the chloride shifts in and out of cells in response to the O2 level in the blood," do they mean in and out of the red blood cells? is chloride mainly found in the extracellular fluid and by extracellular fluid, are they referring to blood? and while we're at it, is intravascular fluid considered an extracellular fluid? and is RBC considered extracellular since it is present in the blood?

i know that each chloride that leaves is replaced by a bicarbonate and for each chloride that enters, a bicarbonate leaves. but i guess my question is where and how is that related to the big picture?

here's how i currently see it or maybe how i'm trying to make sense of it but i'm not sure:

the bicarbonate (HCO3-) leaves the RBC and goes to the extracellular fluid (???).

it attracts a hydrogen ion and so it becomes a carbonic acid (H2CO3). and then it enters the RBC (???) and is released as CO2 (+H20).

i don't get where the chloride part is.. sorry if my question is confusing. as you can tell, i'm really confused.. pls help

-kristina

Update:

NOBLE: i'm not really sure how to comment on my question so i'm just going to "add details."

first off, thaaaaank you!!! i think i finally get it. but here's my answer to your follow up question just to make sure.

"Based on chloride levels, how can I know if I got a plasma from venous blood or arterial blood."

i don't really know the normals or the values for chloride levels but there would be a higher level of chloride in the plasma from arterial blood because the RBC is still carrying O2 (versus CO2). meaning there would be no dumping of CO2 in the blood which would've combined with H2O in the RBC to become H2CO3 which would have become a bicarb that would normally (or at least prefer to) stay in the plasma.

since the RBC doesn't lose a -charge, there is no need for the Cl- to go in which means that it would still be in the plasma. thus, a higher level of Cl- in the arterial plasma versus the venous.

did i make sense? and did i get your point??

4 Answers

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  • 1 decade ago
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    hey kabb good question, heme buffer is kind of complicated.

    Let's start by answering definitions so we start on the same page. You already know that there are RBC in blood. Now you need to know that blood also has plasma. Plasma is the non-cellular part of blood. If you take blood and separate all the cells from it, you would get a yellow liquid, that's plasma. Intracellular just means inside a cell, extracellular means the opposite... outside a cell. In the context of our discussion, intracellular means inside the RBC (RBC is a cell after all, right) and extracellular is referring to the plasma.

    The word intravascular just refers to something within the blood vessel (the blood, including RBC and plasma are intravascular) and extravascular would be things outside the blood vessel (skeletal muscles, fat these are all extravascular).

    So one more time: Blood is generally intravascular. There are 2 main components in blood, the cells (RBC) and the plasma (liquid). The RBC is a cell, so when we say intracellular it means insides RBC, when we say extracellular we mean plasma (for this discuss). Make sure you get this because this is your first confusion and books like to use these words a lot.

    Now for the real discussion. Btw i suggest you find a picture or something in your book to follow along, because i just confused myself reading over this. Anyway, you obviously know we breathe in oxygen, our body uses it and the bi-product is CO2. This CO2 has to be transported to the lung through the blood so it can be exhaled out. The problem is CO2 is normally a gas, and we can't have gas in our blood vessels. So our body hides the CO2 in the form of bicarb which is a liquid. that's the main concept

    (your 2nd confusion build on your first confusion because you didn't understand intracellular vs extracellular) To get the concept we'll start with CO2. Your body makes C02 and dumps it into the blood. The RBC sees this and quickly grabs the CO2, Once the CO2 is inside the RBC (intracellular) it combines with water to make H2CO3. H2CO3 becomes H+ and HCO3- (bicarb).This bicarb is free to stay inside the RBC or go outside into the plasma (prefers outside). If it goes out, the RBC will lose a -charge. To keep the charges inside and outside the RBC balanced, a chloride (cl has a - charge) comes into the RBC from the plasma. Well, this is how CO2 is transported through the whole body till it gets to the lung (pretty sneaky, right). I hope that all made sense.

    Ok, now final step in the process... once the blood gets to the lung the bicarb comes into the RBC from the plasma (again switching places with a cl to need the charges neutral). pretty much the whole process reverses... bicarb combines with H+ ->H2CO3 which get broken down into CO2 and H2O. CO2 is now free to leave the RBC and go out into the lungs where it can be breathed out. THAT'S IT, mission accomplished!!

    A note worthy point here you might want to memorize... CO2 + H2O =>H2CO3 (and vice versa) this reaction is done by a enzyme called "carbonic anhydrase." This is VERY unique enzyme that is ONLY found in RBCs. We can make H2CO3 from water and co2 anywhere else. Any decent college professor will probably ask this on an exam.

    Well I think that is all I say about this topic. ""the chloride shifts in and out of cells in response to the O2 level in the blood," do they mean in and out of the red blood cells?" yes they mean in and out of RBC. So if you think you fully understood the topic answer this question:

    Based only on chloride levels, how can I know if I got a plasma from venous blood or arterial blood. Write your answer as a comment.

    Source(s): 3rd yr Medical Student Hint for question: go back to high school bio. What is the general basic difference between artery and veins? (don't think directions)
    • miykey076 years agoReport

      Carbonic anhydrase is found in MANY other parts of the body and not just in red blood cells

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  • thorp
    Lv 4
    3 years ago

    Hemoglobin Buffer System

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  • Anonymous
    5 years ago

    This Site Might Help You.

    RE:

    hemoglobin buffer system?

    i'm a confused about this hemoglobin buffer system.. sorry if this is going to be a little long! i think i'm mainly confused about the basics..

    i know that this system uses chloride shifts to maintain acid-base balance.

    but when they say "the chloride shifts in and out of cells in...

    Source(s): hemoglobin buffer system: https://tr.im/5Yq3S
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  • Anonymous
    6 years ago

    we check the level of chlorine ions in the blood sample, if high then it's arterial blood because the RBCS are not carrying co2 yet, and if low then it's venous blood ,and chlorine ions have entered the RBCS and replaced bicarbonate ions which means that CO2 molecules have entered the RBCS.

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