6.2.2 - Amino Acids, Amides and Chirality Flashcards
What are amino acids?
The building blocks of biological molecules called peptides and proteins.
What are proteins called?
Polypeptides.
How many different amino acids are there in the body?
20
What are alpha amino acids?
Both the basic amine group (NH2) and the acid carboxyl group are bonded to the same carbon atom.
What is the general formula for an amino acid?
RCH(NH2)COOH
What kind of carbons do amino acids generally have?
Chiral carbons.
What can amino acids act as?
An acid or a base (they are amphoteric).
What part of amino acid reacts with bases/alkalis?
The COOH group. The base removes H+ to produce the carboxylate salt, COO-
What part of amino acid reacts with acids?
NH2 group. The acid supplies H+ to produce an ammonium salt, NH3+
Amino acids with alcohols and what conditions?
Forms an ester with concentrated sulphuric acid catalyst.
What is a zwitterion?
Where an internal salt can be formed due to the acidic carboxyl group (COOH) and the basic amine group (NH2) in the amino acid interacting.
What happens when a zwitter ion is formed?
A proton is transferred from the acidic carboxyl group to the basic amine group.
What is the charge on a zwitterion?
The ion contains a positive and negative charge so has no overall charge.
What is the isoelectric point?
The specific pH at which an amino acid exists as a zwitterion.
What happens to the zwitterion when H+ ions are added?
Acts as a base and so accepts a proton forming NH3+
What happens to the zwitterion when OH- ions are added?
Acts as an acid, donating a proton.
What is chirality?
When a carbon has 4 different groups attached to it.
What does a molecule containing a chiral carbon have?
No plane of symmetry so has a non-superimposable mirror image. These molecules are called optical isomers (enantiomers)
What do optical isomers do?
Rotate plane polarised light by equal amounts in opposite directions.
What does a racemic mixture mean?
The mixture contains equal amounts of both optical isomers so does not rotate plane polarised light.
Are carbons in the benzene ring chiral?
No.
What is an amide?
Contains an acyl group attached to a nitrogen.
Primary amide structure?
The nitrogen atom has 2 hydrogens and they have the general formula RCONH2
Secondary amide structure?
The nitrogen atom has 1 hydrogen and they have the general formula RCONHR’
How are primary amides produced?
Reaction of acyl chloride and ammonia.
RCOCl + NH3 ->
RCONH2 + HCl
RCOCl + 2NH3 ->
RCONH2 + NH4Cl
How are secondary amides formed?
The reaction of an acyl chloride with a primary amine.
