Introduction to Proteins Flashcards
When are there equal amounts of protonated and deprotonated forms (50:50) of a side chain (R)?
When the pKa is equal to the pH
pH higher than pKa
Deprotonated
pH lower than pKa
Protonated
Non-polar side chains? (-philic or -phobic?)
Hydrophobic (found on the inside of molecules)
What are the non-polar side chains?
Glycine (Gly, G), Alanine (Ala, A), Valine (Val, V), Leucine (Leu, L), Isoleucine (Ile, I), Methionine (Met, M), Phenylalanine (Phe, F), Tryptophan (The, T), Proline (Pro, P).
Polar side chains? (-philic or -phobic?)
Hydrophilic (good for Hydrogen bonding - Ser, The, Tyr (through -OH groups), Asn, Gln (through C=O or NH2 groups).
What are the polar side chains?
Serine (Ser, S), Threonine (The, T), Cysteine (Cys, C), Tyrosine (Tyr, T), Asparagine (Asn, N), Glutamine (Gin, G).
What are electrically charged side chains (-philic or -phobic?)
Hydrophilic
What are the electrically charged (negative) side chains?
Acidic: Aspartic acid (Asp, D), Glutamic acid (Glu, E)
What are the electrically charged (positive) side chains?
Basic: Lysine (Lys, K), Arginine (Arg, R), Histidine (His, H)
Acidic side chains (-) charge
Can lose proton (Asp, Glu)
Basic side chains (+) charge
Can gain a proton (Lys, Arg, His)
Special cases: Glycine
Small (only attached to an H atom), can fit into small spaces and gives flexibility
Special cases: Cysteine
Can form cross-links (disulphide bonds) - very stable
Special cases: Proline
Proline is kinky and rigid
