Sowseii
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#1
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Hi guys currently doing an assignment for biochemistry I’ve been asked which forms of amino acid would be present in pH 7 and pH 9, protonated, deprotonated, zwitterion or neutral? I would really appreciate any help
Thanks!
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adina456
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#2
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Are there any amino acids in particular that were mentioned?
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Sowseii
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#3
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#3
(Original post by adina456)
Are there any amino acids in particular that were mentioned?
Hi, the amino acid is asparagine
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adina456
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#4
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(Original post by Sowseii)
Hi, the amino acid is asparagine
okay, the basic anime group (NH3) of amino acids are able to accept a proton from the carboxylic group to form an ion containing both a negative and positive charge - this is called a zwitterion (the charges for both groups are now NH3^+ and COO^-

the isoelectric point is the pH at which the zwitterion is formed (for asparagine it’s pH 10.76)

If the amino acid is placed in a solution with a pH GREATER than its isoelectric point, the amino acid behaves as an acid and the NH3^- group loses a proton (deprotonated). The opposite occurs for a solution with a pH LESS THAN the amino acids isoelectric point, it acts as a base and the COO^- group gains a proton (protonated)

For asparagine:
pH7 - protonated
pH 9 - also protonated

Hope this helped, for more clarity I would research zwitterions
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Kallisto
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(Original post by Sowseii)
x

Just as an addition to adina456 explanations, I will give you an understanding what exactly happens to the amino acid placed in a solution with a pH 10.76, the value for asparagine. As you already know, it is a protonation, as pH 9 and pH 7 are lesser than 10.76.

When adding a certain amino acid in this solution, the amino acid becomes a zwitterion which has two different charges now, a positive (NH3+) and a negative (COO-) one. In other words: the functional groups of the amino acid are ionized. In this process, the Carboxyl group (COOH) donated a proton (H+) to the amino group (NH2) which gained it and this zwitterion state is done.

Acting like a base means that the COO- is protonated in solution and gets back to the carboxyl group COOH, while the NH3+ ion remains. It would be vice versa, when the amino acid acts like an acid: NH3+ donates a proton and get back to amino group NH2, while the COO- ion remains. That is the deprotonated process.
Last edited by Kallisto; 2 years ago
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Sowseii
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#6
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#6
(Original post by adina456)
okay, the basic anime group (NH3) of amino acids are able to accept a proton from the carboxylic group to form an ion containing both a negative and positive charge - this is called a zwitterion (the charges for both groups are now NH3^+ and COO^-

the isoelectric point is the pH at which the zwitterion is formed (for asparagine it’s pH 10.76)

If the amino acid is placed in a solution with a pH GREATER than its isoelectric point, the amino acid behaves as an acid and the NH3^- group loses a proton (deprotonated). The opposite occurs for a solution with a pH LESS THAN the amino acids isoelectric point, it acts as a base and the COO^- group gains a proton (protonated)

For asparagine:
pH7 - protonated
pH 9 - also protonated

Hope this helped, for more clarity I would research zwitterions
Hi, thanks for the response! This helps a lot
(Original post by Kallisto)
Just as an addition to adina456 explanations, I will give you an understanding what exactly happens to the amino acid placed in a solution with a pH 10.76, the value for asparagine. As you already know, it is a protonation, as pH 9 and pH 7 are lesser than 10.76.

When adding a certain amino acid in this solution, the amino acid becomes a zwitterion which has two different charges now, a positive (NH3+) and a negative (COO-) one. In other words: the functional groups of the amino acid are ionized. In this process, the Carboxyl group (COOH) donated a proton (H+) to the amino group (NH2) which gained it and this zwitterion state is done.

Acting like a base means that the COO- is protonated in solution and gets back to the carboxyl group COOH, while the NH3+ ion remains. It would be vice versa, when the amino acid acts like an acid: NH3+ donates a proton and get back to amino group NH2, while the COO- ion remains. That is the deprotonated process.
Hi! Thanks the the response this helped a lot!
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Sowseii
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#7
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#7
(Original post by adina456)
okay, the basic anime group (NH3) of amino acids are able to accept a proton from the carboxylic group to form an ion containing both a negative and positive charge - this is called a zwitterion (the charges for both groups are now NH3^+ and COO^-

the isoelectric point is the pH at which the zwitterion is formed (for asparagine it’s pH 10.76)

If the amino acid is placed in a solution with a pH GREATER than its isoelectric point, the amino acid behaves as an acid and the NH3^- group loses a proton (deprotonated). The opposite occurs for a solution with a pH LESS THAN the amino acids isoelectric point, it acts as a base and the COO^- group gains a proton (protonated)

For asparagine:
pH7 - protonated
pH 9 - also protonated

Hope this helped, for more clarity I would research zwitterions
Hi, thanks for the response I actually understand it now!
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