Amino Acids Flashcards
characteristics of non polar R groups
-will NOT form hydrogen bonds or participate in ionic interactions
which aromatic R groups are non polar
Phenylalanine
tryptophan
which aromatic R group is polar
tyrosine
characteristics of uncharged polar R groups
-hydrophilic
-like to participate in hydrogen bonds but not ionic interactions
characteristics of polar positively charged R groups
-hydrogen bond donors
-like to participate in ionic interactions
characteristics of polar negatively charged R groups
-like to participate in ionic interactions
-hydrogen bond acceptors
how to read a hydropathy scale
High + positive: highly hydrophobic
low + positive/negative: slightly hydrophilic
High + negative: Highly hydrophilic
what does a small pKa describe
the acid is more acidic/likely to donate a proton
average pKa of a carboxyl group
2
average pKa of an amino group
9
if pH is greater than pKa what form is the ion in
deprotonated form
Amino acids with ionizable side chains(9)
Lysine
Arginine
Histidine
Glutamic acid
Aspartic Acid
Cysteine
Tyrosine
Serine
Threonine
pKa of Asp side chain
3.7
pKa of Glu side chain
4.3
pKa of His side chain
6
pKa of Cys side chain
8
pKa of Tyr and Lys side chain
10
pKa of Arg side chain
12
pKa of Thr and Ser side chain
13
what is the isoelectric point(pI)
pH at which the molecule carries no net charge
why is it important to know pI
compounds are less soluble when they have no net charge
equation for pI
pI = 1/2 (pKa1 = pKa2)
-pKa1 and pKa2 are the pKas on opposite sides of the isoelectric point
enantiomers
mirror images
how are peptide bond formed/broken
water is removed/added
(OH removed from COOH, H removed from NH2)
pKa of carboxyl in a polypeptide
3.5
pKa of amino in a polypeptide
8.5
