Amino Acids Flashcards
What is an a-amino acid?
Organic molecules containing a carboxylic acid group and amine group bonded to the same carbon atom.
Which amino acid is the only amino acid that is not chiral?
Aminoethanoic acid (glycine)
Why are all amino acids chiral molecules?
All amino acids contain a chiral carbon atom bonded to four separate groups.
Amino group, carboxylic group, hydrogen and R group
How are amino acids amphoteric?
They have both acidic and basic properties. They have a basic amino group and an acidic carboxylic group
What is a Zwitterion?
Depolar ion which means it has a positive charge in one part of the molecules and a negative charge in another part of the molecule.
What happens when an alkali is added to an amino acid Zwitterion?
The NH3+ group donates a hydrogen ion to the OH- ions of the alkali to form water. The organic compound is no longer a Zwitterion because it only contains a negative charge.
What happens when an acid is added to an amino acid Zwitterion?
The COO- group accepts a hydrogen ion from the acid. The organic compound is no longer a Zwitterion as it only contains a positive charge.
Why do amino acids have a relatively high melting points?
In the solid state, the Zwitterion is the usual form that an amino acid exists in. This means there are strong ionic attractions between neighbouring Zwitterions in the solid, so a large amount of energy is required to break the ionic attractions.
Explain the solubility of amino acids in water
Amino acids are generally soluble in water because strong ionic attractions form between the Zwitterions and the polar water molecules.
How does a peptide bond form?
During a condensation reaction between 2 amino acids. A water molecule is lost.
What is the difference between a dipeptide and a polypeptide?
Dipeptide is formed from 2 amino acids while a polypeptide is formed from more than 2 amino acids.
How do polypeptides lead to protein formation?
Polypeptides are chains of more than 2 amino acids joined together by peptide links, when the chain becomes very long, they can fold into proteins.
What is the primary structure of a protein ?
sequence of amino acids which make up the polypeptide chain
What is the secondary structure of a protein?
The protein chain has peptide links which can form hydrogen bonds with each other. Leading to 2 possible shapes of the chain (the secondary structure ):
- a helix spiral
- b pleated sheet
Both established by hydrogen bonding
What is the tertiary structure of a protein?
Relates to the extra bonds which can form between different parts of the polypeptide chain, determine how the a-coils or b-pleated sheets of the protein fold with respect to each other. The types of extra bonds include ionic and hydrogen bonds and disulphide bridges
