Chapter 1: Amino Acids, Peptides, and Proteins Flashcards
Explain the difference between aspartic acid and asparagine.
aspartic acid has a hydroxyl group (OH) where asparagine has an amino group (NH2)
more???
How is the direction of light rotation (clockwise vs anticlockwise) determined for a given amino acid?
experimentally
L vs D does not indicate the direction in which optically active molecules rotate light
Which amino acid is NOT chiral?
glycine (it has 2 H groups on its alpha carbon)
Are most chiral amino acids L or D? What is the exception?
stereochemistry
most amino acids are L-amino acids
exception: cysteine
amphoteric meaning
can act as either an acid or a base
pka meaning
the pH at which the species will lose its hydrogen ion
[HA] = [A-] (half of the molecules are deprotonated, half are protonated)
zwitterion
a molecule with both a positive and negative charge, but is overall neutral
titration: midpoint
PH = pKa
the point at which enough titrant has been added to neutralize half of the analyte
[acid] = [base]
solution is acting as a buffer
titration: equivalence point
pH = pI
pI
amino acids with neutral R groups
pka1: carboxyl group
pka2: amino group
pI
amino acids with basic R groups
pka2: amino group (NH3+)
pka3: R group
pI
amino acids with acidic R groups
pka1: carboxyl group (COO-)
pka3: R group
amino acids are read from – to – terminus
N to C terminus
average weight of 1 amino acid
110 Da
protein dimer
two protein monomers which are (usually) non-covalently bonded
homodimer
a dimer of 2 identical protein monomers
heterodimer
a dimer composed of 2 different protein monomers
