Identifying Specific Protein Structures - Biochemistry

Arginine is a basic amino acid. The charge on the amine in the functional group makes this structure basic. While lysine is also a basic amino acid, it has a different R-group.

Methionine is a non-polar amino acid. It is one of two amino acids that contain sulfur, the other is cysteine.

Leucine is a non-polar amino acid with a R-group.

The interior portion of a transmembrane protein is most likely to be populated with smaller, hydrophobic amino acids. This is because the interior of the transmembrane protein is in the hydrophobic environment of the lipid bilayer. Thus, alanine, valine, and leucine - small, hydrophobic amino acids - are most likely to be found there.

The secondary structure of a protein can be either an alpha helix or a beta pleated sheet. In either case, the structure forms due to intra-chain hydrogen bonding of the protein's backbone amino and carboxyl groups.

All 20 of the amino acids have on its central carbon a hydrogen, a carboxyl group, an amino group, and a distinctive R-group. These R-groups determine the properties of the amino acid and thus the polypeptide of which they are a part.

Primary protein structures are composed of amino acids linked together by peptide bonds. Secondary protein structures are held together by hydrogen bonds. Phosphodiester bonds can be found between sugar and phosphate groups in the backbone of DNA.

The amino acid's R group is composed of an ethyl group, followed by a carboxylate group, and therefore represents glutamate.

The amino acid's chiral carbon is connected to two methyl groups followed, by a sulfur, and finally another methyl group. Therefore, the amino acid is methionine (M).

The structure would most closely resembe tyrosine (pictured).

Alanine is the amino acid that would be formed by removing the phenyl group from phenylalanine (the pictured molecule).

Threonine (pictured here) would be formed.

Cysteine is a polar amino acid with an R-group of . It is one of two amino acids with a sulfur in the R-group, the other is methionine.

The polarity of an amino acid is determined by the R-group. The electronegativity difference between oxygen and carbon creates a dipole with the partial positive being on carbon and the partial negative being on oxygen. The dipole makes the molecule polar.

Phenylalanine is a non-polar amino acid. The structure of this amino acid is literally alanine with a phenyl group attached.

An acidic amino acid must have a carboxyl moiety in its R-group. Because all amino acids contain a carboxyl moiety on the alpha carbon, that acidic group does not determine whether or not the amino acid is considered acidic.

Bases, according to the Bronsted-Lowry definition, are substances that accept

Aspartic acid is an acidic amino acid, meaning it contains in its R-group. The R-group of aspartic acid is .

Glutamine is one of two amino acids that are amides. The nitrogen bonded to a carbon-oxygen double bond makes it an amide.