LEARNING OBJECTIVE - amino acids

Zwitterion

A neutral compound having formal unit electrical charges of opposite sign

Chiral center

Carbon attatched to 4 different groups

Enantiomers

Non superimposable mirror images

• share same physical properties, different biological properties

Stereoisomers

Molecules with the same formula and atom connections but different 3D shapes in space

Optically active

Chiral molecules are called this because they rotate the plane of polarized light

• + clockwise, -counterclockwise

Why do we still use the fisher D-L for amino acids

Because it describes similarities across all amino acids. L (levorotatory) is left and D (dextrorototary)is right.

Thus if the amino group is on the left its a L-amino acid

What configuration is used by living cells

L-amino acid

What amino acid has an R configuration and why

Cysteine is the only chiral amino acid with an R config because it has a sulfur atom (heavier than the carboxyl group)

Why is chiraity important using ibuprofen and thalidomide

• receptors and enzymes are chiral so theyre very specific when it comes to the enantiomers

• In ibuprofen, the S configuration relieves pain whereas the R configuration is inactive

• In thalidomide, the R configuration is a mild sedative while the S configuration causes birth defects and is a teratogen

What does glx indicate

Glu or gln (gln can be hydrolyzed to glu)

What does asx indicate

It’s Asp or asn (asn can be hydrolyzed to asp)

Draw a peptide bond connecting two amino acids