Ch 1: Amino Acids, Peptides, Proteins Flashcards
amino acids have 4 groups attached to the central alpha carbon
amino group
carboxylic acid group
hydrogen atom
R group
___ amino acids appear in the proteins of eukaryotic organisms
20
stereochemistry of alpha carbon for all aa in euk is
L
D-amino acids exist in
prokaryotes
all aa except ___ have (S) configuration
cysteine
all aa except ___ are chiral
glycine
nonpolar, nonaromatic
glycine alanine valine leucine isoleucine methionine proline
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Aromatic aa
Phenylalanine
Tyrosine
Tryptophan
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Polar aa
Serine Glutamine Threonine Asparagine Cysteine
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Positively Charged - basic aa
Lysine
Arginine
Histidine
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Negatively Charged - acidic aa
Aspartate
Glutamate
DE
pKa of a group is the pH at which half of the species is ____ ; HA = A-
deprotonated
aa exist in different forms at diff pH
low acidic pH, aa ___
pH near pI of aa ___
high alkaline pH, aa __
fully protonated
neutral zwitterion
fully deprotonated
isoelectric point (pI) of an aa w/o charged group can be calculated by
averaging the 2 pKa values
aa can be titrated:
titration curve nearly flat ____
nearly vertical when at the ____
at pKa values of the aa
pI of the aa