Chapter 3 Flashcards
(57 cards)
All amino acids have…
an alpha-carbon and four substituents
What is an alpha-carbon?
a chiral center when all four substituents are different
The spatial distribution of individual amino acids is…
tetrahedral
What distinguishes one amino acid from the other?
the chemical nature of the R group
What amino acid is the only one that is achiral?
Glycine (G)
What two amino acids contain two chiral centers?
Isoleucine (I) and Threonine (T)
When do pKa values of amino acids change?
polymerization
What are enantiomers?
mirror images of each other
The D and L system is used to…
indicate amino acid absolute configuration
What amino acids are predominant in nature?
L-amino acids
For nonpolar amino acids R groups are subject to the…
hydrophobic effect in proteins
What are the essential amino acids for nonpolarR groups?
V, I, M and L
for aromatic R groups what are the essentials?
F and W
For polar, uncharged R groups what can they form?
hydrogen bonds
Cysteine can form…
disulfide bonds
What is the essential R groups for polar, uncharged?
T
What are the essential amino acids for positively charged R groups?
K and H
For negatively charged R groups both have a net negative charge at what pH?
7.0
Pro and Lys are common in…
collagen and aid in protein structure stability
Four Lys form…
Desmosine, a component of elastin
Glu is carboxylated in pro-thrombin to produce…
thrombin
What is Zwitterion?
dipolar ion
What is the isoelectric point (pI)?
The pH at which the net electric charge is zero
For a molecule with only two functional groups the Zwitterion is found…
between the two pKa values
