BioChem Amino Acids

Hydrophobic Amino Acids

• Have nonpolar side chains of different shapes and sizes that: Do not interact well with polar substances such as water and pack together to form compact structures

• tryptophan = bulkiest hydrophobic amino acid; contains an indole group in its side chain and has potential for hydrogen bonding

Glycine (Gly, G)

Alanine (Ala, A)

Proline (Pro, P)

Valine (Val, V)

Leucine (Leu, L)

Isoleucine (Ile, I)

Methionine (Met, M)

Tryptophan (Trp, W)

Phenylalaline (Phe, F)

Polar Amino Acids

• Side chains that make polar amino acids hydrophilic and more reactive than hydrophobic amino acids

• cysteine = contains a sulfhydryl (thiol, –SH) group– Pairs of –SH groups can form disulfide bonds

• histidine = often found in enzyme active sites

Serine (Ser, S)

Threonine (Thr, T)

Tyrosine (Tyr, Y)

Asparagine (Asn, N)

Glutamine (Gln, Q)

Cysteine (Cys, C)

Histidine (His, H)

Positively Charged Amino Acids

• Positive refers to likely charge at physiological pH; highly hydrophilic

• Arginine: contains a guanidinium group

Lysine (Lys, K)

Arginine (Arg, R)

Negatively Charged Amino Acids

• Negative refers to likely charge at physiological pH

• Carboxylic functional group

• Protonated (aspartic and glutamic acid) only at a highly acidic pH

Aspartate (Asp, D)

Glutamate (Glu, E)