Amino Acids Flashcards
How are the 20 amino acids classified?
by their R group properties
Which amino acids are hydrophobic??
Gly Ala Val Leu Ile Pro Met Phe Trp
Why can prolines affect structural flexibility of polypeptides?
b/c it has. distinctive amino group NH2 group which forms a cyclic structure making it rigid
Is cysteine hydrophilic or hydrophobic?
hydrophobic even though it is classified as a polar amino acid
Which amino acids has a secondary amino group or imino group?
proline since its imino group forms a cyclic structure
When transferring an amino acid from a non-polar solvent to water and we get delta G < 0, what does this telll us about the reaction?
that the transfer is favorable and the reaction is hydrophilic
When transferring an amino acid from a non-polar solvent to water and we get delta G > 0, what does this telll us about the reaction?
the transfer is unfavorable and the amino acid is hydrophobic
The hydropathy index is directly proportional to what?
Gibbs free energe (delta G of the transfer).
If we have a large positive hydropathy index number, what would this tell us about our amino acid?
this would reflect higher hydrophobicity
Base on hydropathy index, which amino acid is more hydrophobic?
Isoleucine: 4.5 or alanine with 1.8 hydropathy index
They’re both hydrophobic since the number is positive, but isoleucine is higher thus more hydrophobic
What are the two ionizable groups in amino acids and what is their pka?
COOH to COO- + H+ has pka of 2.2
NH2 + H+ = NH3+ has a pka 9.4
You have a carboxyl group and it is placed in a pH of 4 is will it be protonated or deprotonated
deprotonated b/c anything above 3.5 is negative charge
What does it mean when an amino acid is amphoteric at physiological pH?
that the amino acid posses both acid and base properties
what does it mean when an amino acid is zwitterionic?
both positive and negative charges in the same molecule (their charge cancels out)
the isoelectric point is what?
the pH at which the amino acid has neutroa charge or net zero charge (zwitterionic)