Flashcards in Amino Acids and Proteins Deck (18):
Amino acids contain what two functional groups.
• amine NH2• carboxyl COOH
What is an a amino acid?
There are four different groups attached to the central (chiral) carbon.Chiral molecules have two optical isomers called enantiomers.
What is a zwitterion?
A dipolar ion- it has both a positive and negative charge in different parts of the molecule.Only exist near an amino acid's isoelectric point.
What is the isoelectric point?
This is the pH where the average overall charge on the amino acid is zero.
How are peptides formed?
α-amino acids can join up together to form peptides via an amide or peptide link• 2 amino acids joined dipeptide• 3 amino acids joined tripeptide• many amino acids joined polypeptide
Peptides can be broken down into their constituent amino acids by...
Hydrolysis• attack takes place at the slightly positive C of the C=O• the C-N bond next to the C=O is broken• hydrolysis with just water is not feasible• hydrolysis in alkaline/acid conditions is quicker• hydrolysis in acid/alkaline conditions (e.g. NaOH) will produce salts
What are proteins?
• polypeptides with high molecular masses• chains can be lined up with each other• the C=O and N-H bonds are polar due to a difference in electronegativity• hydrogen bonding exists between chainsun
State the general formula of an a amino acid.
What is thin layer chromatography?
This separates components by adsorption.A solvent spreads up the plate as it is dipped into a solvent.The different substances move up with it but at different rates- so they separate out.
How do you work out what was in the mixture in thin layer chromatography?
Calculating Rf value = distance travelled by spot/ distance travelled by solvent, you can then look them up in a table of known values.
What's a racemic mixture?
A solution in which both enantiomers of a compound are present in equal amounts is called a racemic mixture, or racemate. Problem is only one enantiomer may be help and the other may be harmful.
If the conditions are more acidic than the isoelectric point...
The -NH2 group is likely to be protonated.
If the conditions are more basic than the isoelectric point...
The -COOH group is likely to lose its proton.
What is meant the term stereoisomer?
Molecules with the same structure but different arrangements in space.
How does cis-trans isomerism arise?
The double bond does not rotate.
What structural feature causes optical isomerism in organic molecules?
Molecules with optical isomers...- are chiral- have four different groups attached to the carbon- the mirror images cannot be superimposed
What's a chiral carbon?
Carbon which has four different groups attached to it. It's possible to arrange the groups in different ways to create enantiomers or optical isomers.