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Oxygen pH and CO2

Discussion in 'DAT Discussions' started by Zerconia2921, May 16, 2008.

  1. Zerconia2921

    Zerconia2921 Bring your A-game!
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    I am having trouble understanding the physio of when CO2 increase in tissues and PH decrease.

    Is oxygen being dumped into the tissue or what some text say uploading? I dont understand the context of uploading. Is hemoglobin attaching to it?
    Can anyone help? :)
     
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  3. userah

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    increase in CO2 is linked with Ph decrease. This is because when there is an increase of CO2 in cells, there is also an increase of H+ ions, which is the reason for the pH decrease (more acidic). When a question asks for what happens when there is a CO2 increase or a pH decrease, they're both asking the same thing. It means that there is CO2 buildup and hemoglobin is going to "dump" more O2 to offset that acidity.

    hope that made sense. =)
     
  4. creative8401

    creative8401 Im Anush Hayastan
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    Hello. Userah did a well job, and let me add to that post.

    Carbon dioxide (a gas), is insoluble in mostly water conditions. This is seen, for example, if you leave a cup of water at room temperature, there are bubbles in the water. This is one of the problems that the human body has to overcome, and it does so by "transforming" (if thats the right word in this case) into bicarbonate. You have to understand that CO2 is not simply carried as a gas in the red blood cells. Bicarbonate as a matter of fact is probably the highest molecule in quantity you can find in the body. Let me show you a formula as to what happens:

    CO2 + H2O → H2CO3 → H+ + HCO3−.

    At the end, once bicarbonate forms, it liberates an H+, which is acidic and as a result, decreases the pH of the environment. The arteries leading to the heart and brain, for instance, do not sense the levels of "CO2" but rather the the drop in pH. If the pH level drops, that means a high amount of CO2 is present. Remember CO2 cannot be carried as a gas but transformed into bicarbonate which liberates an H+. Hope this makes sense.

    Thanks.

    PS: If you have DAT Destroyer, check out question 216 from bio section. =)
     
  5. Zerconia2921

    Zerconia2921 Bring your A-game!
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    So when hemogoblin dumps O2 its free to attach to the CO2 to remove it from the body?
     
  6. creative8401

    creative8401 Im Anush Hayastan
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    Hi Zerconia2921. As long as you understand that "attach" means carrying out the production to bicarbonate, then you have an understanding of the concept.

    When you say attach, it does not attach to CO2 it carries out the production of bicarbonate on the surface of the red blood cells. Now you may ask, how does it get rid of the carbon dioxide in the lungs. The answer would be that the reaction I put above is reversible, carried out by enzymes in the lining of the lungs. Once CO2 is formed, it leaves to the alveoli by diffusion.

    Please note, try to obtain a conceptual understanding of the material. Once you understand the big picture, then the DAT concepts become easy. Good luck.
     
  7. Hugh Mannity

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    Not all CO2 converts to bicarbonate and protons.

     
  8. userah

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    taking from schaum's, i'll give you a short excerpt which i feel does a pretty good job of explaining what happens to CO2 once it enters the bloodstream from tissues

    Approx 10% is dissolved in plasma (CO2 is 30x more soluble in water than 02). The remainder enters the RBCs. Some of the CO2 associates with the amino groups of the amino acids in the hemoglobin forming carbaminohemoglobin. The remaining RBCs combine with water to form carbonic acid (H2CO3), which quickly dissociates into bicarbonate ions (as creative8401 has stated :)) These reactions occur in the plasma, but the rate is greatly accelerated by enzyme carbonic anydrase.

    Now the part where CO2 diffuses out into lungs...
    When blood reaches the lungs, it encounters low levels of CO2 in alveoli so the carbaminohemoglobin is the first to dissociate back into CO2 and diffuse into lungs where it's exhaled. Because of this, CO2 levels in the blood begin to fall. So what happens is a reverse reaction from that above. (carbonic anhydrase, the enzyme, works both ways. forming HCO3 as well as going backwards to get CO2 and H2O.) So in the lungs, the reverse reaction occurs. As CO2 is being lost from carbaminohemoglobin, to make up for the CO2 lost, bicarbonate undergoes reverse reaction to get CO2 and H2O again. The net result of all these reactions is that in the lungs most of the CO2 that was bound as carbaminohemoglobin or as the bicarbonate that diffused into the plasma is converted back to free CO2 and diffuses into the lungs where it's exhaled.

    It might be a tad confusing, but just read over it slowly a few times and it should all make sense. good luck :)
     
  9. Zerconia2921

    Zerconia2921 Bring your A-game!
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    ü Increase in CO2 means the reaction of CO2 + H20 àH2COà H+ HCO3-­ dissociates and builds up H+ concentration that results in lower pH.
    ü Our bodies carry majority of our CO2 as bicarbonate HCO3- not as CO2 gas because CO2 is insoluble in liquid form so is transformed into bicarbonate and carbaminohemoglobin via enzyme carbonic anhydrase.
    ü When blood reaches lungs alveoli the carbaminohemoglobin dissociates into CO2. The CO2 is exhaled out of the lungs.
    ü This causes a drop in CO2 in body. Then enzyme carbonic anhydrase dissociates HCO3- into water and CO2. The CO2 is transformed into carbaminohemoglobin and bicarbinate. When carbaminohemoglobin reaches the lungs it dissociates CO2 again.
    [FONT='Verdana','sans-serif']I hope I got this down now. Thanks Userah, and Creative8401 for your input really apperciate it. :thumbup:
     
  10. userah

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    haha not a problem. thanks should go out to you as well for bringing it up. gives me a good chance of going over the material and helps me really understand it as I explain. so thank you =)
     
  11. Hugh Mannity

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    There was a study that showed that tutoring (or teaching in general) is more beneficial to the tutor than the student! :eek: weird huh. I'm glad i tutor and TA chem and bio now...
     
  12. userah

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    haha def agree with you. the only way to really tell if you understood something or not is to see if you can help someone else understand it. if you can't describe it, then you don't have a full grasp of the material.
     

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