D-amino acids

Question 1

Describe isomerism in amino acids

Answer 1

The standard alpha amino acids, all but glycine can exist in either of two optical isomer, called L or D amino acids which are mirror images if each other

Question 2

What are L amino acids?

Answer 2

These amino acids are found in proteins during translation in the ribosome

Question 3

What are D amino acids?

Answer 3

They are found some proteins produced by enzyme posttranlational modifications after translation and translocation to the endoplasmic reticulum

Question 4

Where are D amino acids found?

Answer 4

As in some exotic sea dwelling organisms such as cone snails, they are also abundant components of the peptidoglycan cell walls of bacteria and D-serine may act as a neurotransmitter in the brain

Question 5

What does L and D convention for amino acid configuration refer to?

Answer 5

Not to the optical activity of the amino acid itself, but rather to the optical activity of the isomer of glyceraldehyde from which that amino acid can theoretically be synthesised

Question 6

What does the ‘D’ refer to in D-amino acid?

Answer 6

Dextrorotatory

Question 7

What does ‘L’ refer to in L-amino acid?

Answer 7

Levorotaory

Question 8

Which amino acid has sulfur in it?

Answer 8

Cysteine

Question 9

What is rhe CO-R-N rule?

Answer 9

A simple mnemonic for correct L form is “CORN” when the alpha carbon atom is viewed with the H in front, the residues read CO-R-N in a clockwise direction