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Decide if the side chains of the amino acid residues in the following peptides are nonpolar or polar, and label the hydrophobic and hydrophilic end of each peptide.
- VLLFGEDEK
- RKVSFLGAA
(a)
Interpretation:
The polarity of the side chains of the amino acid residue in the given peptide should be determined and also label the hydrophilic and hydrophobic ends of the given peptide.
VLLFGEDEK
Concept Introduction:
Amino acids are organic compounds containing two functional groups namely amino and carboxylic group. Amino group is attached to the alpha carbon, carbon adjacent to the carbonyl group making them alpha amino acids.
This table gives information about the polarity of the side chains:
| Name of Amino Acid | One-letter abbreviation | Structure | Side chain Polarity | Side chain |
| Alanine | A |  | Nonpolar | Hydrophobic |
| Asparagine | N |  | Polar | Hydrophilic |
| Cysteine | C |  | Nonpolar | Hydrophobic |
| Glutamine | Q |  | Polar | Hydrophilic |
| Glycine | G |  | Nonpolar | Hydrophobic |
| Isoleucine | I |  | Nonpolar | Hydrophobic |
| Leucine | L |  | Nonpolar | Hydrophobic |
| Methionine | M |  | Nonpolar | Hydrophobic |
| Phenylalanine | F |  | Nonpolar | Hydrophobic |
| Proline | P |  | Nonpolar | Hydrophobic |
| Serine | S |  | Polar | Hydrophilic |
| Threonine | T |  | Polar | Hydrophilic |
| Tryptophan | W |  | Nonpolar | Hydrophobic |
| Tyrosine | Y |  | Polar | Hydrophilic |
| Valine | V |  | Nonpolar | Hydrophobic |
| Aspartic acid | D |  | Polar | Hydrophilic |
| Glutamic acid | E |  | Polar | Hydrophilic |
| Arginine | R |  | Polar | Hydrophilic |
| Histidine | H |  | Polar | Hydrophilic |
| Lysine | K |  | Polar | Hydrophilic |
Answer to Problem 56P
The polarity of the side chains of amino acids are shown along with hydrophobic and hydrophilic end of the given peptide 'VLLFGEDEK' as follows:
Explanation of Solution
Side chains of amino acids are non-polar because only carbon and hydrogen atoms are present having very small dipole moment and tends to repel water. That's why non-polar amino acids are hydrophobic in nature.
Side chains of amino acids are polar because these proteins have those toms which are capable of forming hydrogen bonds have very high dipole moment and tends to attract water. That's why polar amino acids are hydrophilic in nature.
From the table, the sequence of peptide contains the following amino acids:
V = Valine is a non-polar amino acid.
L = Leucine is a non-polar amino acid.
F = Phenylalanine is a non-polar amino acid.
G = Glycine is a non-polar amino acid.
E = Glutamic acid is a polar amino acid.
D = Aspartic acid is a polar amino acid.
K = Lysine is a polar amino acid.
From the given peptide sequence 'VLLFGEDEK', Valine present at the right end and Lysine present at the left end of the sequence.
Valine is a non-polar amino acid and hydrophobic in nature.
Lysine is a non-polar amino acid and hydrophilic in nature.
Hydrophobic and hydrophilic ends along with polar and non-polar amino acids are indicated in the given sequence as follows:
(b)
Interpretation:
The polarity of the side chains of the amino acid residue in the given peptide should be determined and also label the hydrophilic and hydrophobic ends of the given peptide.
RKYSFLGAA
Concept Introduction:
Amino acids are organic compounds containing two functional groups namely amino and carboxylic group. Amino group is attached to the alpha carbon, carbon adjacent to the carbonyl group making them alpha amino acids.
Answer to Problem 56P
The polarity of the side chains of amino acids are shown along with hydrophobic and hydrophilic end of the given peptide 'RKYSFLGAA' as follows:
Explanation of Solution
Side chains of amino acids are non-polar because only carbon and hydrogen atoms are present having very small dipole moment and tends to repel water. That's why non-polar amino acids are hydrophobic in nature.
Side chains of amino acids are polar because these proteins have those toms which are capable of forming hydrogen bonds have very high dipole moment and tends to attract water. That's why polar amino acids are hydrophilic in nature.
From the table, the sequence of peptide 'RKYSFLGAA' contains the following amino acids:
R = Arginine is a polar amino acid.
K = Lysine is a polar amino acid.
Y = Tyrosine is a polar amino acid.
S = Serine acid is a polar amino acid.
F = Phenylalanine is a non-polar amino acid.
L = Leucine is a non-polar amino acid.
G = Glycine is a non-polar amino acid.
A = Alanine is a non-polar amino acid.
From the given peptide sequence 'RKYSFLGAA', Arginine present at the right end and Alanine present at the left end of the sequence.
Arginine is a polar amino acid and hydrophilic in nature.
Alanine is a non-polar amino acid and hydrophobic in nature.
Hydrophobic and hydrophilic ends along with polar and non-polar amino acids are indicated in the given sequence as follows:
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Chapter 21 Solutions
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