13.3) Leucine is an essential amino acid; the body cannot produce it from other compounds, so it must be present in the diet. Draw the predominant form of leucine when the pH = 1.0, pH = 7.4, and pH = 12.0 (include lone pairs). H pH = 1.0 H :0: H H-N-C-C-0-H || CH₂ CHCH3 CH3 At pH = 1.0 (an extremely acidic solution) the pH is less than the pK, of both the carboxyl group and the quaternary ammonium group, therefore both groups exist in their acid forms, as shown above. physiological pH (pH = 7.4) H H :0: H-N C 1 CH₂ H CHCH3 CH3 Quaternary ammonium groups have pk₁ values of about 9.5, therefore, at pH = 7.4, the acid form (quaternary ammonium group) is predominant. H- N pH = 12.0 H H :0: The pKa values of carboxyl groups are between 2 and 5 (depending on which amino acid), therefore, at pH = 7.4, the base form (carboxylate ion) is predominant. The side-chain of leucine is not polar acidic or polar basic, so it is not affected by pH. C- CH₂ CHCH3 CH3 At pH = 12.0 (an extremely basic solution) the pH is greater than the pK, of both the carboxyl group and the quaternary ammonium group, therefore both groups exist in their base forms, as shown above. C
13.3) Leucine is an essential amino acid; the body cannot produce it from other compounds, so it must be present in the diet. Draw the predominant form of leucine when the pH = 1.0, pH = 7.4, and pH = 12.0 (include lone pairs). H pH = 1.0 H :0: H H-N-C-C-0-H || CH₂ CHCH3 CH3 At pH = 1.0 (an extremely acidic solution) the pH is less than the pK, of both the carboxyl group and the quaternary ammonium group, therefore both groups exist in their acid forms, as shown above. physiological pH (pH = 7.4) H H :0: H-N C 1 CH₂ H CHCH3 CH3 Quaternary ammonium groups have pk₁ values of about 9.5, therefore, at pH = 7.4, the acid form (quaternary ammonium group) is predominant. H- N pH = 12.0 H H :0: The pKa values of carboxyl groups are between 2 and 5 (depending on which amino acid), therefore, at pH = 7.4, the base form (carboxylate ion) is predominant. The side-chain of leucine is not polar acidic or polar basic, so it is not affected by pH. C- CH₂ CHCH3 CH3 At pH = 12.0 (an extremely basic solution) the pH is greater than the pK, of both the carboxyl group and the quaternary ammonium group, therefore both groups exist in their base forms, as shown above. C
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I don't get it at all. I struggled with this question. I need help with the predominant form of leucine of the Henderson-Hasselbalch when the pH = 1.0, pH = 7.4, and pH = 12.0 (include lone pairs). Can you help me to explain to me, please?
Transcribed Image Text:13.3) Leucine is an essential amino acid; the body cannot produce it from other compounds, so it must be present in the diet.
Draw the predominant form of leucine when the pH = 1.0, pH = 7.4, and pH = 12.0 (include lone pairs).
H.
H
+
|
H
pH = 1.0
H :0:
|
||
C
C-O-H
|
CH₂
|
CHCH3
I
CH3
At pH = 1.0 (an extremely acidic solution)
the pH is less than the pK₂ of both the
carboxyl group and the quaternary
ammonium group, therefore both groups
exist in their acid forms, as shown above.
physiological pH (pH = 7.4)
:O:
||
C-8:
H
H
L |
+
H-N
|
H
C
I
CH₂
T
CHCH₂
|
CH3
Quaternary ammonium groups have pKa
values of about 9.5, therefore, at pH = 7.4,
the acid form (quaternary ammonium
group) is predominant.
pH = 12.0
H
:0:
I ||
H-N-C
I
H
C-8:
The pK₂ values of carboxyl groups are
between 2 and 5 (depending on which
amino acid), therefore, at pH = 7.4, the base
form (carboxylate ion) is predominant.
The side-chain of leucine is not polar acidic or polar basic, so it is not affected by pH.
T
CH₂
|
CHCH3
|
CH3
a
At pH = 12.0 (an extremely basic solution)
the pH is greater than the pK₂ of both the
carboxyl group and the quaternary
ammonium group, therefore both groups
exist in their base forms, as shown above.
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