Amino Acid's And Proteins Flashcards
Give the meaning of each of the three terms used to describe the levels of protein structure (3)
– Primary structure describes sequence of amino acid’s via peptide bonds
– Second airy structure describes shape taken up by protein chain such as alpha helix structure or beta pleated sheets
– Tertiary structure describes the further folding to give overall shape due to extra bonds
Describe how paper chromatography can be used to identify an unknown amino acid (6)
-pencil line on paper (bottom) put spot of mixture on the line
– Place in beaker containing solvent (ensure solvent below of spot)
– Cover with watch glass
– When solvent nearly reaches top, Markwest solvent is
– Identify position of spots and allow to dry then Spray with ninhydrin solution
– Workout RF values or if done understand the conditions you standard RF tables
What is the equation for Rf value?
Distance travelled by spot/distance travelled by solvent
What is another word for amino acid monomers?
Amino acid residues
What is the name of the link between Amy and group and a carboxylic acid group?
Peptide link
Describe the process of making a dipeptide(2)
–Amine group of one amino acid reacts with carboxylic acid group of another amino acid
– in a condensation reaction
Describe the process of breaking down a protein into its individual amino acid’s(5)
– In a hydrolysis reaction
– Add hot aqueous 6 mol dm^-3 HCl
– Keep it under reflux for 24 hours
– This produces ammonium salt of amino acid
– Final mixture neutralised using a base
Explain why spots travel different distances in paper chromatography(2)
– Different substances have different solubilities
– Therefore as solvent spreads up paper different chemicals in mixture move with it but at different rates
Define amphoteric
Contains both acidic and basic properties
What is a zwitterion?
Overall neutral molecule with both positive and negative charge in different parts of molecule
And amino acid can only exist as a zwitterion near its isoelectric point.what is an isoelectric point?
The pH where overall charge on amino acid is zero
Is isoelectric point the same for all amino acid’s?
Depends on R group
Describe what happens when amino acid is placedo in more acidic conditions than isoelectric point(2)
– Amine group becomes protonated to NH3 +
– COO- group become COOH
Describe what happens when amino acid is placed in more basic conditions than isoelectric point (2)
– COOH group loses protons to become COO-
– NH3+ becomes NH2
What happens when amino acid is exposed to isoelectric point?
Both carboxyl group and amino group likely to be ionised forming zwitterion
Why does tertiary structure occur?
Different forces occur due to the R groups of the amino acid to keep it stable
Name the forces that can hold a tertiary structure (4)
– Instantaneous dipole -induced dipole
– Ionic interactions
– Hydrogen bonds
– Disulphide bonds
