Biochemistry Amino Acid

Ala, A

Alanine

Arg, R

Arginine

Asn, N

Asparagine

Asp, D

Aspartic Acid

Cys, C

Cysteine

Gln, Q

Glutamine

Glu, E

Glutamic Acid

Gly, G

Glycine

His, H

Histidine

Ile, I

Isoleucine

Leu, L

Leucine

Lys, K

Lysine

Met, M

Methionine

Phe, F

Phenylalanine

Pro, P

Proline

Ser, S

Serine

Thr, T

Threonine

Trp, W

Tryptophan

Tyr, Y

Tyrosine

Val, V

Valine

Alanine

Non-polar, hydrophobic, nonessential amino acid

Arginine

Basic, hydrophilic, nonessential amino acid

Asparagine

Polar, hydrophilic, nonessential amino acid

Aspartic Acid

Acidic, hydrophilic, nonessential amino acid

Cysteine

Polar, hydrophilic, nonessential amino acid

Glutamine

Polar, hydrophilic, nonessential amino acid

Glutamic Acid

Acidic, hydrophilic, nonessential amino acid

Glycine

Polar, hydrophobic, nonessential amino acid

Histidine

Polar, hydrophilic, essential amino acid

Isoleucine

Non-polar, hydrophobic, essential amino acid

Leucine

Non-polar, hydrophobic, essential amino acid

Lysine

Basic, amphipathic, essential amino acid

Methionine

Non-polar, amphipathic, essential amino acid

Phenylalanine

Non-polar, hydrophobic, essential amino acid

Proline

Non-polar, hydrophobic, nonessential amino acid

Serine

Polar, hydrophilic, nonessential amino acid

Threonine

Polar, hydrophilic, essential amino acid

Tryptophan

Non-polar, amphipathic, essential amino acid

Tyrosine

Polar, amphipathic, nonessential amino acid

Valine

Non-polar, hydrophobic, essential amino acid

Cationic Form

This form of an amino acid occurs at low pH, where the amino and carboxyl group are protonated, resulting in a positively charged molecule (Gly1).

Zwitterionic Form

This form of an amino acid is the neutral state of an amino acid (Gly0) where the carboxyl group is deprotonated and the amino group is protonated, balancing the positive and negative charges in the molecule.

Anionic Form

This form of an amino acid occurs at high pH, where both the carboxyl group and the amino group are deprotonated, resulting in a negatively charged species (Gly2).

Isoelectric Point (pI)

This value is the pH at which an amino acid or peptide carries no net electric charge, resulting in a neutral state. It is calculated by averaging two pKa values of the side chains. For acidic and basic amino acids, these pKas are the two most acidic or basic values respectively.

Enantiomers

Nonsuperimposable mirror images of a molecule, are chiral, and present in all amino acids except Glycine.

L-enantiomer

Virtually all amino acids exist in what enantiomer form?

D- and L-enantiomer

What are the two forms of enantiomer amino acids can exist in?

Cysteine

Which amino acid contains a thiol group that can form disulfide bonds?

Serine

Which amino acid has a side chain that can form hydrogen bonds and is classified as polar?

Lysine

Which of the following amino acids contains a positively charged side chain at physiological pH?

The sequence of amino acids in a polypeptide chain

What is the primary structure of a protein?