Chapter 1 concepts Flashcards
how many standard amino acids are there?
20
what is the pKa for all alpha carboxilic amino acids?
2.1
what is the pKa for all the alpha amino groups?
9.5
how do you find all amino acids at physiological pH of 7.4?
they are all ionized (NH3; amino group has a positive charge, COO; carboxyl group has a negative charge)
what amino acid contains a secondary amino group?
proline
how do you find all alpha carboxyl’s at low pH?
protonated (from COO- to COOH)
what is the isoelectric point?
pH at which an amino and carboxyl group are ionized.
the charges of the amino acid combined make the amino acid neutral
If the amino acids placed in a solution and polarized light is made to pass through the solution, all amino acids will rotate towards what side?
left
What is the simplest amino acid?
glycine
where can glycine be found?
bends and turns
what are the branched amino acid?
valine, isoleucine, leucine
what are the sulfur containing amino acids?
cysteine, methionine
what sulfur containing amino acid has its sulfur free to make bonds?
cysteine
what amino acids is formed by joining of two sulfurs of cysteine?
cystine
what happens with proline’s amino group?
it is not really free since is helps with its ring formation
What is special about proline?
it is a helix breaker, it changes the alpha helix to other shape.
what are the aromatic amino acids?
phenylalanine, tyrosine, tryptophan
what are the basic amino acids?
arginine and lysine due to additional NH2 group
what is so special about histidine?
it can accept or donate protons so its a good buffer
What are the acidic amino acids?
aspartic acid and glutamic acid due to extra COOH group
What are the neutral amino acids?
aparagine and glutamine
What are the hydroxyl containing amino acids?
serine, threonine, tyrosine
what are hydroxyl in amino acids are the site of?
site for post-translational modification like phosphorylation or glycosylation
What does it mean the more positive the hydropathic index is?
the more hydrophobic the side chain of the amino acid will be.
What are the nonpolar amino acids?
glycine, alanine, branched amino acids, proline
where do you find nonpolar amino acids?
in the hydrophobic core of a protein molecule or in the transmembrane portion.
What aromatic amino acid is nonpolar?
phenylalanine
is tyrosine polar or non polar?
it is polar due to its OH
is tryptophan polar or nonpolar?
it is polar
what amino acids are polar uncharged?
amino acids that have amide or hydroxyl groups; asparagine, glutamine, serine, threonine, cysteine
in proteins where do you find polar uncharged amino acids?
in the surface
