F324 - Amino Acids And Chirality Flashcards
Define an alpha-amino acid.
An alpha-amino acid is when the amino and carboxyl groups are on the same carbon atom.
What is the general formula for an alpha-amino acid?
RCH(NH2)COOH (except proline).
What is a zwitterion?
Is a dipolar amino acid. A proton is lost from the carboxylic acid and a dative bond is made between the proton and the lone pair of the nitrogen atom. It has no net charge; it is a neutral iron.
Define the term isoelectric point.
Is the pH value at which the amino acid exists as a zwitterion.
What determines the value of the isoelectric point?
The R group of the amino acid. A carboxylic acid R group will lower the isoelectric point and an amine R group will raise the isoelectric point.
Are amino acids soluble in: A) aqueous acid? B) water? C) aqueous base? Describe, if any, the change to the amino acid structure.
A) soluble; amine group(s) is protonated
B) insoluble
C) soluble; carboxyl group(s) can be deprotonated.
Describe the formation of a peptide bond.
Amino acids link together with the elimination of a water molecule to form a peptide (or amide) linkage. This is called a condensation reaction because a small molecule is formed.
Define the term hydrolysis.
It is the splitting of water by reaction with another compound.
What is acid hydrolysis?
Acid hydrolysis of a protein requires 6 moldm-3 HCl, refluxed for 24 hours. The products are amino acids with a protonated amine group.
What is base hydrolysis?
It requires an aqueous base such as NaOH. The products are amino acids with a deprotonated carboxyl group (COO-Na+ in this case).
Define the term stereoisomerism.
They are compounds with the same molecular formula and structural formula but have a different spatial arrangement of their atoms.
Define the term optical isomers (or enantiomers).
Are stereoisomers that are non-superimposable mirror images of each other.
What is a chiral carbon?
It is a carbon atom attached to 4 different atoms or groups of atoms.
In natural processes only one out of the two optical isomers of amino acids are produced. Why is this?
Because the enzymes are stereospecific.
Describe the pharmaceutical effects of chiral drugs.
One isomer may be pharmacologically inactive, whilst the other produces the desired effect. One isomer may produce serious side-effects which seriously affect the health of the patient.
