Amino Acids Flashcards
Draw the general structure of an amino acid.
Why are amino acids considered amphoteric?
They can act as acids since the carboxyl group can donate a proton. They can act as bases since the amine group can accept a proton.
Why do amino acids showcase optical isomerism?
The chiral carbon usually has 4 different groups attached to it.
Draw the structure of 2-aminoethanoic acid.
Draw the structure of 2-amino-3-methylbutanoic acid.
What is a zwitterion?
An ion that has both a positive and negative charge.
When do amino acids become zwitterions?
At their isoelectric point.
What happens if you put the amino acid in acidic conditions?
The amine group gains a proton and the carboxyl group remains unchanged.
What happens if you put the amino acid in alkali conditions?
The carboxyl group loses a proton and the amine group remains unchanged.
What happens if the amino acid is near its isoelectric point?
The amine group gains a proton and the carboxyl group loses a proton. The amino acid has become a zwitterion.
What are proteins?
Many amino acids are joined together by peptide links.
Draw the two dipeptides that can form when alanine bonds with glycine.
What are the conditions needed to hydrolise a protein into amino acid?
6 mol dm-3 of HCL
heat under reflux for 24 hours
What is the primary structure of a protein?
The sequence of amino acids.
What is the secondary structure of a protein?
Hydrogen bonds form between the peptide links and the chain folds into a 2D structure. This can either be an alpha helix or a beta-pleated sheet.
What is the tertiary structure of a protein?
The formation of more hydrogen bonds, disulfide bridges and ionic bonds causes the chain to fold into its 3D shape.
Draw how hydrogen bonds form in the polypeptide chain.
Draw how disulfide bridges form between cysteine amino acids.
Where do ionic bonds form in the polypeptide chains?
Between the positive and negative ends of the zwitterions.
Why are enzymes considered biological catalysts?
They speed up chemical reactions without being used up.
What is the lock and key model?
For a reaction to be catalysed, the substrate must fit into the active site of the enzyme.
Why are the active sites of enzymes considered stereospecific?
Only one enantiomer of the amino acid will fit into the active site of the enzyme and the other won’t so a reaction can’t be catalysed with that enantiomer.
What are inhibitors?
molecules that have the same shape as the substrate so they can bond with the active site instead of the substrate.
What does the relative amount of inhibition depend on?
The concentration of the inhibitors and substrates.
Why can you use thin-layer chromatography to separate amino acids?
They all have slightly different solubilities meaning some of them will be more attracted to the stationary phase compared to others.
What can be used to stain the amino acids to make them visible?
- Nihydrin solution which causes the amino acids to turn purple.
- A plate that contains fluorescent dye.
How does the fluorescent dye help us identify the amino acids?
When under UV light the amino acids will cover the dye and make certain spots look darker.
