M4: Amino Acids and Peptides

The building blocks of proteins, consisting of an amino group and a carboxyl group attached to a central carbon atom.

• Amino acids

• Nucleotides

The 20 naturally occurring α-amino acids used by cells to synthesise proteins.

• Alpha amino acids

• Beta amino acids

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: H

Glycine has the simplest R group, which is just a single hydrogen. It is nonpolar and the smallest amino acid.

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: CH₃

Alanine has a methyl group (CH₃) as its R group, making it nonpolar and relatively small.

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: (CH₃)₂CHCH₂

Valine's R group is a branched, nonpolar isopropyl group, which contributes to its hydrophobic character.

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: (CH₃)₂CHCH₂CH₂

Leucine's R group is a branched isobutyl group, which is nonpolar and hydrophobic.

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: CH₃CH₂CH(CH₃)CH₂

Isoleucine has a branched R group with an isopropyl side chain, making it nonpolar and hydrophobic

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: C₆H₅

Phenylalanine has an aromatic benzyl group in its R group, which is nonpolar and hydrophobic.

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: (CH₂)₃NH

Proline's R group forms a cyclic structure with its amino group, contributing to its unique properties, but it is considered nonpolar.

Identify which Amino acid with a nonpolar R group is shown.

(Amino acid, 3L Abbreviation, 1L Abbreviation, R-Group)

(a)  

Answer explanation

R group: C₈H₆NCH₂CH₂CH₂

Tryptophan's R group includes an aromatic indole ring, which is nonpolar and hydrophobic.