Biology question Watch

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lil_crazyflakes
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#1
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#1
Why do proteins both absorb and release hydrogen ions? Is it to do with acting as a buffer in the blood?

Why does the pH of body fluids fall during excercise? :confused:
Please help, thankyou
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Twiglet
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dont really know about the proteins, but the pH of body fluids falls during exercise as during exercise carbon dioxide is produced. This dissolves in body fluids ( eg blood) and lowers its pH - making it more acidic. It is this lowering of pH of the blood in particular which plays a factor in the regulation of breathing and heart rate.
Hope that helped a little bit!
franks x
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lil_crazyflakes
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(Original post by franks)
dont really know about the proteins, but the pH of body fluids falls during exercise as during exercise carbon dioxide is produced. This dissolves in body fluids ( eg blood) and lowers its pH - making it more acidic. It is this lowering of pH of the blood in particular which plays a factor in the regulation of breathing and heart rate.
Hope that helped a little bit!
franks x
Thankyou
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Ramaya
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#4
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(Original post by lil_crazyflakes)
Why do proteins both absorb and release hydrogen ions? Is it to do with acting as a buffer in the blood?
I'm guessing its because they are made up of amino acids. Amino acids accept hydrogen on the NH2 group forming NH3+ part but it can also release hyrdogen ions from the COOH group forming COO-. It accepts/releases them depending on the surrounding acidity.
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oxymoron
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(Original post by Ramaya)
I'm guessing its because they are made up of amino acids. Amino acids accept hydrogen on the NH2 group forming NH3+ part but it can also release hyrdogen ions from the COOH group forming COO-. It accepts/releases them depending on the surrounding acidity.
Don't forget that in proteins, most of these groups are involved in the peptide bonds, so it is only the terminal COOH and NH2 that can be involved in proton transfers.
However many of the side chains can donate or accept protons (eg aspartate, glutamate, lysine, histidine) and these often act as acids and bases in enzyme catalysed reactions.
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visesh
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(Original post by franks)
dont really know about the proteins, but the pH of body fluids falls during exercise as during exercise carbon dioxide is produced. This dissolves in body fluids ( eg blood) and lowers its pH - making it more acidic. It is this lowering of pH of the blood in particular which plays a factor in the regulation of breathing and heart rate.
Hope that helped a little bit!
franks x
Don't forget that lactic acid levels might rise too, decreasing the pH
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Twiglet
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Don't forget that lactic acid levels might rise too, decreasing the pH
ah yes, thanks, is that because the lactic acid dissociates to form lactate and H+ ions - the H+ causing the acidity?

And to do with the protien stuff, i vaguely recall something about zwitter ions - dont know what relevance that has here, if any !
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visesh
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(Original post by franks)
ah yes, thanks, is that because the lactic acid dissociates to form lactate and H+ ions - the H+ causing the acidity?

And to do with the protien stuff, i vaguely recall something about zwitter ions - dont know what relevance that has here, if any !
yup.

well IIRC, zwitterions are ions that can carry both a negative and positive charge, making them good buffers.

(Original post by random website)
Zwitterions make good buffer solutions — they resist change to the pH of a solution by selective ionisation. In the presence of acids, zwitterions accept the hydrogen ions, removing them from the solution. In the presence of bases, zwitterions donate hydrogen ions to the solution, again balancing the pH.
Like someone mentioned earlier, only the terminal aas in a protein can do this. Some side groups can do this too.
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SB
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(Original post by visesh)
Don't forget that lactic acid levels might rise too, decreasing the pH
That's not in the blood though... is it? :confused:
*worries she's revised the wrong thing*
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visesh
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(Original post by skevvybritt)
That's not in the blood though... is it? :confused:
*worries she's revised the wrong thing*
http://www.brianmac.demon.co.uk/lactic.htm

there is some LA in the blood, and the levels rise as you exercise i think.
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