Lecture 1 Flashcards
α-carbon is chiral in all aa except
glycine
what is chirality
non-superimposible mirror images
all aa found in natural proteins are what type of aa?
L-amino acids
what does the R group side chain do?
gives the aa different properties
what is a zwitterion?
A zwitterion is a compound which contains a positive and negative charge, but with no overall electrical charge
what are aa residues?
single aa within a protein
what are the essential aa? which ones are they?
These are aa acquired throughout the diet; not created by the body.
histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine, lysine
what are the conditionally non-essential aa? which ones are they?
these are aa required at some stage of growth or by some people who can’t synthesize them b/c of genetics or medical condition.
arginine, asparagine, glutamine, glycine, proline, serine, tyrosine
what are the non-essential aa? which ones are they?
these are aa our bodies can synthesize.
alanine, asparatate, cysteine, glutamate
which aa’s are the non polar, aliphatic?
glycine (G), alanine (A), proline (P), Leucine (L), Isoleucine (I), Valine (V), Methionine (M).
Y are the non polar, aliphatic aa important? Where are they usually located?
They are important for hydrophobic protein interactions. They tend to be inside protein structures.
what is special about proline?
- its a very rigid molecule
- it’s more like an imino acid than aa
- α-amino group is actually a secondary amine
- can disrupt the folding structures like α-helix or β- pleated sheets
- commonly found in sharp turns connecting β strands
- proline reduces flexibility b/c of it’s 2° amino group structure
which aa’s are polar, uncharged?
serine (S), threonine (T), Cysteine (C), Asparagine (N), Glutamine (Q)
what is polarity due to?
- OH groups
- S atom
- amide groups
Why are the polar, uncharged aa important? Where are they usually located?
these groups can form H bonds with H2O, therefore they are hydrophilic. They are usually found on the surface of protein structures.
What special functions do the polar uncharged aa have?
- OH of S/T are sites for covalent modifications (ex. phosphorylation)
- Cys forms covalent disulfide bonds important for protein folding
- Asn & Gln are important N donors/carriers; can also participate in H bonding
What stabilizes the secondary structure of a protein?
hydrogen bonds
What aa are aromatic?
phenylalanine (F), tyrosine (Y), tryptophan (W)
Why are aromatic aa important?
- relatively non-polar so can participate in hydrophobic interactions
- absorb light at 280nm; useful for protein quantitation
What aa are positively charged (basic)?
histidine (H), arginine (R), lysine (K)
what causes an aa to be positively charged? what causes an aa to be negatively charged?
- positively charged b/c of the amino group (NH3+) side chains
- negatively charged b/c of the carboxyl group (COO-) side chains
What aa are negatively charged (acidic)?
aspartate (D), glutamate (E)
salt bridges stabilize what structure?
tertiary structure
what is transamination?
Transamination (or aminotransfer) is a chemical reaction between two molecules. One is an amino acid, which contains an amine (NH2) group. The other is a keto acid, which contains a keto (=O) group.
