10.1 amino acids, peptides, and proteins Flashcards
amino acid structure
how does glycine differ from the other amino acids
it is NOT chiral because its R group is hydrogen
the other amino acids are all chiral because the alpha carbon is attached to 4 different groups
all naturally occurring amino acids in eukaryotes are ____(L/D) -isomers
L-isomers
Fischer projection of amino acids
How doe cysteine differ from the other amino acids
it is R configuration
while all other L-amino acids have S configuration
the carboxyl group of an amino acid is _______ (acidic/basic)
acidic; can lose an H+ ion
the amino group of an amino acid is _______ (acidic/basic)
basic; can pick up an H+ ion
amino acids are amphoteric (define)
can act as both acids and bases
amino acids form zwitterions in solution (define)
a molecule with charges which “cancel” each other out
the amino group becomes protonated and bears a +1 charge
the carboxyl group becomes deprotonated and bears a -1 charge
5 categories of amino acids
non polar nonaromatic
aromatic
polar
negatively charged (acidic)
positively charged (basic)
aromatic amino acids include:
tryptophan
phenylalanine
tyrosine
(those with benzene rings)
what type of reaction forms peptide bonds
condensation reaction
peptide bond formation
polypeptides form when amino acids undergo condensation to form peptide bonds between them
peptide bond cleavage
via hydrolysis of the peptide bond
catalyzed by a strong acid or base
resonance stabilization of peptide bonds
partial double bond character between the nitrogen atom and the carbonyl carbon (no rotation around the C-N bond)
