Amino Acid part1 Flashcards
Alpha carbon has what type of symmetry?
Asymmetry
asymmetry allows for what type of isomer?
stereo
What are the 2 types of stereo isomers?
L and D
Proteins consist of mainly what stereo isomer
L
Simplest way to remember the spatial orientation of groups about the alpha carbon of L amino acids is
CORN
L amino acids all have the same what?
Stereochemistry, the side chain R group is in the same position
L amino acids dont all do what the same?
Dont all rotate plan polarised light the same way
D and L amino acids can be made from
Their glyceraldehyde precursor
Side chain angles can be described by what and what are they called
By dihedral/torsion angles, chi angles. X
pKa is what?
Is pH when HA=A-, 50% ionisation
Which amino acids have ionisable C terminal side chains? And what are their pKas roughly
Asp
Glu
His
pKas are less than 7
Which amino acids have ionisable N terminal side chains? and what are their pKas
Cys Tyr Lys Arg pKas are more than 8
One letter coding and three letter coding for
Glutamic Acid
Glu, E
One letter coding and three letter coding for
Aspartic Acid
Asp, D
One letter coding and three letter coding for
Arginine
Arg, R
One letter coding and three letter coding for
Lysine
Lys, K
One letter coding and three letter coding for
Histidine
His, H
One letter coding and three letter coding for
Asparagine
Asn, N
One letter coding and three letter coding for
Glutamine
Gln, Q
One letter coding and three letter coding for
Threonine
Thr, T
One letter coding and three letter coding for
Tyrosine
Tyr, Y
One letter coding and three letter coding for
Proline
Pro, P
One letter coding and three letter coding for
Tryptophan
Trp, W
Which amino acids have a negative side chain? So which ones produce COO-
Aspartic Acid and Glutamic Acid. Lose their H, proton donor
Which amino acids have a positive side chain? So which ones produce NH3+
Arginine, Lysine and Histidine
Which are the polar amino acids?
Asparagine Glutamine Serine Threonine Tyrosine
Difference between aspartic acid and glutamic acid?
Glutamic Acid has an extra methyl
Glutamic Acid and Aspartic Acid are polar or nonpolar?
Very polar
Glutamic acid and aspartic acid often act as what?
Chelators of metal ions
How do chelates work?
The oxygens form a coordinate complex with a metal.
Eg Ca2+ in the middle, surrounded by 6 oxygens from other molecule such as from Asp or Glu
Basic side chains have what charge?
Positive
How many methyl groups in total in
a) Asp
b) Glu
a) 1
b) 2
How many methyl groups in
a) Lysine
b) Arginine
c) Histidine
a) 4
b) 3
Arginine has what group?
Guanidino, so 3 separate NH groups
Guanidino group has what feature?
Is planar and stabilised by resonance. The charge is delocalised over the whole group
Histidine has what group
Imidazole ring
The imidazole ring has what properties?
Nucleophile (deprotonated form) or electrophile
Histidine is highly used where?
In enzyme active sites
Asn and Gln have what side chain?
Amide
Uncharged polar side chain
The amide side chains have what character?
Partial double bond character, group planar like peptide bond
Difference between Serine and Threonine and what do they have in common?
Both have OH, so hydroxyls
Threonine has a methyl group but after the carbon whereas no methyl groups for serine. So threonine has extra chiral centre
Phe, Tyr and Trp have what in common and what are their differences?
All aromatic (nonpolar rings) Tyr has OH, somewhat polar and can hydrogen bond. Trp has indole ring
Trp has the following properties
a) what does it absorb?
b) rich in what
c) donor for
a) absorbs UV + fluorescent
b) Electron rich so negative charge transfer
c) Indole NH H bond donor
Phe, Tyr and Trp can absorb wavelengths but which absorbs the most?
Trp
Aliphatic side chains are what?
Hydrophobic
Valine has how many methyl groups but they are what?
2 methyl but they are beta branched
Comparison between Val, Leu and Isoleucine
Leu is a longer version of Val with an extra methyl pushing the branching to the gamma section
Isoleucine has what in comparison to leucine?
An extra methyl so an extra chiral centre
