Chapter 18, Problem 18.34UKC

Draw the structure of the following amino acids, dipeptides, and tripeptides at low pH (pH 1) and high pH (pH 14). At each pH, assume that all functional groups that might do so are ionized. (Hint: See Worked Example 18.2.)

(a)    Val

(b)    Arg

(c)    Tyr-Ser

(d)    Glu-Asp

(e)    Gln-Ala-Asn

(f)    Met-Trp-Cys

Interpretation Introduction

Interpretation:

Amino acid, valine at low $pH$ and at high $pH$ has to be drawn.

Concept Introduction:

• Many amino acids are linked together through amide bonds to form a biologically large molecule known to be proteins.
• Amino functional group is $(-N{H}_2)$ and carboxyl functional group is $(-COOH)$ and a $R$ (alkyl) group is considered as side chain, when all these are bonded to same carbon atom.
• Zwitterion has both positive as well as negative charge, thus it is also called neutral dipolar ion.
• Zwitterion accepts proton in acidic condition and in basic condition zwitterion lose electrons.
• At low $pH$, amine and carboxylic acid are protonated and at high $pH$ amine and carboxylic acid are deprotonated.

Explanation of Solution

• At low $pH$ the acidity is high and basic groups reacted with $H^{+}$ to form acid compound.

• At high $pH$, the basicity is high, the molecule lose $H^{+}$ which means the base used has deprotonated the hydrogens.

Interpretation Introduction

Interpretation:

Amino acid, Arginine at low $pH$ and at high $pH$ has to be drawn.

Concept Introduction:

• Many amino acids are linked together through amide bonds to form a biologically large molecule known to be proteins.
• Amino functional group is $(-N{H}_2)$ and carboxyl functional group is $(-COOH)$ and a $R$ group is considered as side chain, when all these are bonded to same carbon atom.
• Zwitterion has both positive as well as negative charge, thus it is also called neutral dipolar ion.
• Zwitterion accepts proton in acidic condition and in basic condition zwitterion lose electrons.
• At low $pH$, amine and carboxylic acid are protonated and at high $pH$ amine and carboxylic acid are deprotonated.

Explanation of Solution

• At low $pH$ the acidity is high and basic groups reacted with $H^{+}$ to form acid compound.

• At high $pH$, the basicity is high, the molecule lose $H^{+}$ which means the base used has deprotonated the hydrogens.

Interpretation Introduction

Interpretation:

Dipeptide $\text{Tyr-Ser}$ at low $pH$ and at high $pH$ has to be drawn.

Concept Introduction:

• Many amino acids are linked together through amide bonds to form a biologically large molecule known to be proteins.
• Amino functional group is $(-N{H}_2)$ and carboxyl functional group is $(-COOH)$ and a $R$ group is considered as side chain, when all these are bonded to same carbon atom.
• Zwitterion has both positive as well as negative charge, thus it is also called neutral dipolar ion.
• Zwitterion accepts proton in acidic condition and in basic condition zwitterion lose electrons.
• At low $pH$, amine and carboxylic acid are protonated and at high $pH$ amine ans carboxylic acid are deprotonated.

Explanation of Solution

• At low $pH$ the acidity is high and basic groups reacted with $H^{+}$ to form acid compound.

  

• At high $pH$, the basicity is high, the molecule lose $H^{+}$ which means the base used has deprotonated the hydrogens.

Interpretation Introduction

Interpretation:

Dipeptide $Glu-Asp$ at low $pH$ and at high $pH$ has to be drawn.

Concept Introduction:

• Many amino acids are linked together through amide bonds to form a biologically large molecule known to be proteins.
• Amino functional group is $(-N{H}_2)$ and carboxyl functional group is $(-COOH)$ and a $R$ group is considered as side chain, when all these are bonded to same carbon atom.
• Zwitterion has both positive as well as negative charge, thus it is also called neutral dipolar ion.
• Zwitterion accepts proton in acidic condition and in basic condition zwitterion lose electrons.
• At low $pH$, amine and carboxylic acid are protonated and at high $pH$ amine ans carboxylic acid are deprotonated.

Explanation of Solution

• At low $pH$ the acidity is high and basic groups reacted with $H^{+}$ to form acid compound.

• At high $pH$, the basicity is high, the molecule lose $H^{+}$ which means the base used has deprotonated the hydrogens.

Interpretation Introduction

Interpretation:

Tripeptide $\text{Gln-Ala-Asn}$ at low $pH$ and at high $pH$ has to be drawn.

Concept Introduction:

• Many amino acids are linked together through amide bonds to form a biologically large molecule known to be proteins.
• Amino functional group is $(-N{H}_2)$ and carboxyl functional group is $(-COOH)$ and a $R$ group is considered as side chain, when all these are bonded to same carbon atom.
• Zwitterion has both positive as well as negative charge, thus it is also called neutral dipolar ion.
• Zwitterion accepts proton in acidic condition and in basic condition zwitterion lose electrons.
• At low $pH$, amine and carboxylic acid are protonated and at high $pH$ amine ans carboxylic acid are deprotonated.

Explanation of Solution

• At low $pH$ the acidity is high and basic groups reacted with $H^{+}$ to form acid compound.

• At high $pH$, the basicity is high, the molecule lose $H^{+}$ which means the base used has deprotonated the hydrogens.

  

Interpretation Introduction

Interpretation:

Tripeptide $Met-Trp-Cys$ at low $pH$ and at high $pH$ has to be drawn.

Concept Introduction:

• Many amino acids are linked together through amide bonds to form a biologically large molecule known to be proteins.
• Amino functional group is $(-N{H}_2)$ and carboxyl functional group is $(-COOH)$ and a $R$ group is considered as side chain, when all these are bonded to same carbon atom.
• Zwitterion has both positive as well as negative charge, thus it is also called neutral dipolar ion.
• Zwitterion accepts proton in acidic condition and in basic condition zwitterion lose electrons.
• At low $pH$, amine and carboxylic acid are protonated and at high $pH$ amine ans carboxylic acid are deprotonated.

Explanation of Solution

• At low $pH$ the acidity is high and basic groups reacted with $H^{+}$ to form acid compound.

• At high $pH$, the basicity is high, the molecule lose $H^{+}$ which means the base used has deprotonated the hydrogens.