Amino acids general structure, stereochemistry, classes and properties

Question 1

Structure

Answer 1

Central carbon called 𝛼-carbon which is bonded to a primary amino group and carboxyl group with a side chain

Question 2

Amino acids are chiral

Answer 2

𝛼-carbon is tetrahedral with 4 substituents ∴2 possible configurations
Only glycine is not chiral
Almost all biological occurring amino acids are L-enantiomer

Question 3

Amino acids are Zwitterions

Answer 3

have 2 titratable groups (NH2, COOH)
Can exist in 2 states: NH2 can be +ve or neutral, COOH can be -ve or neutral
pH 5-8 the acids exist in Zwitterionic form– protonated 𝛼-amino and deprotonated 𝛼-carboxyl and has a net charge of 0

Question 4

H bonds

Answer 4

Strength= 2-10 kcal mol-1
Strength of covalent O-H bond in water= 110 kcal mol-1
Water can form electrostatic interactions