Module 3 Flashcards
what 2 forms are amino acids found in?
L and D forms
what form of amino acid are found in proteins?
L stereoisomers
are all amino acids diprotic?
yes
what is the isoelectric point?
net charge on molecule equals zero
what charge will the amino acid have if the pH is below the isoelectric point?
net positive charge
what charge will the amino acid have if the pH is above the isoelectric point?
net negative charge
what is an amino acid?
a peptide of 3 residues
what does simplicity mean in regards to amino acids?
1 type of reaction for polymerization + degradation
what hands do L + D isomers represent?
L = Left hand
D= Right hand
what are the 5 side groups of amino acids?
- non-polar
- aromatic
- polar, uncharged
- polar, positively charged
- polar, negatively charged
what side chains so non-polar amino acids have?
mainly hydrocarbons
what amino acids have sulfur groups for side chains?
methionine & cysteine
what is the smallest amino acid?
Glycine
what amino acid is usually in combo with glycine?
proline
what amino acid can also be considered an aromatic?
Histidine
what is post translational modification?
when some amino acids can be covalently modified after their incorporation into a protein (often reversible)
what are disulfide bonds?
forms through oxidation of sulfhydryl groups of 2 cysteine resiudes to form a covalent linkage
can disulfide bonds be both intermolecular & intramolecular?
yes
what amino acid serves as a proton acceptor and donor?
Histidine
what does diprotic mean?
has 2 buffering regions & can yield 2 H+
what does triprotic mean?
has 3 buffering regions -> have ionizable groups in side chains
what is a zwitterion?
a molecule that has a positively charged & negatively charged group
what is the charge of the zwitterion above the pKa?
negative
what is the charge of the zwitterion below the pKa?
positive
between what range will an amino acid be a zwitterion?
between a pH of 2-10
isoelectric point / neutral zone is calculated by:
pKa1 + pKa2 / 2
how to calculate the average of pKa values?
PI= pKa + pKa2 / 2
what does PI represent?
isoelectric point / average of pKa values
what amino acid forms sulfide bonds?
cysteine
why does histidine have a 0 or + 1 charge?
bc of the imidazole group
