unit 6 section 4 amino acids, proteins and DNA Flashcards
what two functional groups does an amino acid have
it has a carboxyl group (COOH) and an amine group (NH2)
are amino acids amphoteric and what does that mean
yes amino acids are amphoteric, this means that they have the properties of an acid and a base
how can an amino acid act as an acid
they can act as an acid because the carboxyl group is acidic - it can donate an proton
COOH = COO^- + H +
how can an amino acid act as a base
they can act as a base because the amino group ( amine group ) is basic - it can except a proton
NH2 + H^+ = NH3^+
how do you name an amino acid systematically
- find the longest chain that has the carboxylic acid group and write its name
- number the carbons in the chain starting with the carbon in the carboxylic acid group as number 1
- write down the position of any NH2 groups and use the word amino to show that
-write down the name of any other functional groups and say what carbon they are on
what is a zwitterions
amino acids can exist as zwitterions. a zwitterions is an ion that is dipolar - it has both positive and negative charge in different parts of the molecule
where can zwitterions exist and what is an isoelectric point
zwitterions only exist near an amino acids isoelectric point. the isoelectric point is the PH where the overall charge of the amino acid is zero.
when does an amino acid become a zwitterion
an amino acid becomes a zwitterion when its amino group is protonated into NH3^+ and its COOH group is deprotonated into COO^-
what happens to the amino acid when the conditions is more acidic ( low ph ) than the isoelectric point
in conditions more acidic than the isoelectric point, the NH2 group is likely to be protonated but the COOH group is unchanged - so the amino acid will carry positive charge but not a negative charge.
what happens to an amino acid when the conditions is more basic ( high ph ) than the isoelectric point
in conditions more basic than the isoelectric point, the COOH group is likely to loose a proton but the NH2 group will be unchanged - so the amino acid will carry a negative charge but not a positive charge.
in what conditions is a zwitterions formed
only at or near when the isoelectric point are both the carboxylic group and the amino group are likely to be ionised - forming a zwitterion
how do you separate mixtures of amino acids and why does that happen
through thin layer chromatography (TLC)
- this is because the amino acids have different R groups, they will have different solubilities in the same solvent
how do you make an amino acid visible (coloured)
-this can be done by spraying ninhydrin on the plate which will make the amino acid turn purple.
- another way is by using a special plate which has fluorescent dye added to it. the dye glows in UV light. when there are spots of chemicals on the plate, they cover the fluorescent dye - so the spots appear dark.
how do you identify amino acids
this is done by using the chromatogram to calculate the Rf value
what is the formula for the Rf value
Rf = x/y = distance travelled by spot/ distance travelled by solvent
what is a protein and what is it made of
proteins are condensation polymers of amino acids- they are made of up lots of amino acids joined together by peptide links .
explain how two amino acids join together to form a dipeptide
this is done by removing a molecule of water between the two amino acids. and OH from on of the COOH groups will be remove and from the other amino acid a H will be removed from the NH2 group
what happens if two different amino acids combine together
then two different dipeptides will form because the amino acid can join either way round.
how do you break up a protein into its amino acids
you use hydrolysis
what is the method of hydrolysing proteins
this can be done by adding 6 mol dm^-3 of hydrochloric acid, and then heat the mixture under reflux for 24 hours
how do you describe the structure of proteins
proteins are big. so they are describe in four levels, primary, secondary, tertiary and quaternary.
what is the primary structure of an protein
the primary structure is the sequence of amino acids in a long chain that makes up the protein.
what is the secondary structure of a protein
the peptide links can form hydrogen bonds with each other, meaning the chain isnt a straight line. the shape of the chain is called the secondary structure.