DW Lecture 2: Amino Acids and Proteins Flashcards
Which amino acids are considered to have non-polar/hydrophobic side chains?
glycine alanine valine leucine isoleucine phenylalanine tryptophan methionine proline
Which amino acid can be classified as both polar and non-polar? Why?
tryptophan
non-polar in the presence of hydrophobic phenyl ring in the side chain
polar because the nitrogen in the side chain which can form H bonds
Which amino acid can be both charged and uncharged (polar)? Why?
histidine
charged when side chain is protonated
uncharged polar because its pKa is close to physiologic pH so it is deprotonated
Which amino acid can be classified as both non-polar and uncharged polar?
cysteine
due to slightly electronegative sulfur
Which amino acids can be classified as having uncharged polar side chains?
serine threonine tyrosine asparagine glutamine cysteine
Which amino acids have side chains that are acidic (negatively charged) at physiological pH?
aspartic acid
glutamic acid
Which amino acids have side chains that are basic (positively charged at physiological pH)?
histidine
lysine
arginine
What is the difference between a peptide and a protein?
a peptide contains fewer than 50 amino acid
longer chains are called proteins
Where are ionic bonds/salt bridges formed?
between two side chains of opposite charge (e.g. Aspartic acid and Lysine)
What is the amino acid change that often causes sickle cell anemia? Why?
Glu6 Val in the HBB gene
the Glu is hydrophilic and on the surface of the hemoglobin whereas the Val is hydrophobic so it causes hemoglobin to aggregate into fibrils
What are post translational modifications on a molecular level?
the changing of the chemical characteristics of some amino acids after translation of the protein has been completed
normally add a chemical group to the side chain of an amino acid
often reversible
regulated by number of enzymes
What residues are most often phosphorylated?
serine
threonine
tyrosine
(at the hydroxyl)
What residues are most often glycosylated?
serine
threonine
asparagine
What residue is most often acetylated?
lysine (amino group of the side chain)
