Hi Zina,

Here is a organized list of amino acids:

Charged (side chains often form salt bridges):
• Arginine - Arg - R
• Lysine - Lys - K
• Aspartic acid - Asp - D
• Glutamic acid - Glu - E

Polar (form hydrogen bonds as proton donors or acceptors):
• Glutamine - Gln - Q
• Asparagine - Asn - N
• Histidine - His - H
• Serine - Ser - S
• Threonine - Thr - T
• Tyrosine - Tyr - Y
• Cysteine - Cys - C

Amphipathic (often found at the surface of proteins or lipid membranes, sometimes also classified as polar):
• Tryptophan - Trp - W
• Tyrosine - Tyr - Y
• Methionine - Met - M (may function as a ligand to metal ions)

Hydrophobic (normally buried inside the protein core):
• Alanine - Ala - A
• Isoleucine - Ile - I
• Leucine - Leu - L
• Methionine - Met - M
• Phenylalanine - Phe - F
• Valine - Val - V
• Proline - Pro - P
• Glycine - Gly - G

Everything that is not specified as hydrophobic, has hydrophilic properties.
Source: https://proteinstructure...ucture/amino-acids.html

Hi Emma,

Remember that the overall charge on certain amino acids (like histidine) can change depending on the pH of the surrounding environment. So depending on the pH in relation to the pKa of histidine, it can be charged (if its protonated) or uncharged (if its not protonated).

Thanks
Shin

Hi Zina,

SH can kind of be an addition/exception to FON. Cystein is known to form H bonds, especially with ON containing amino acids like asparagine and lysine. Recall that bonding is more like a continuum, and SH containing H bonds are kind of on the edge of this type of behaviour.

I hope this helps,

Katt