Polypeptides (proteins) Flashcards
what is a polypeptide
a chain of amino acids
what two functional groups do amino acid monomers contain
amino and carboxyl group
How many different R groups are there
20
what is a dipeptide
2 amino acids
how is a dipeptide formed
a condensation reaction forms a peptide bond between the carboxyl group of one amino acid and the amine group of another. A water molecule is released in this reaction.
what reagent tests for protein
Biuret
what is biuret reagent
a solution of dilute sodium hydroxide and copper sulfate
what is the primary structure
the order/structure of amino acids (R-groups) in a polypeptide chain
what determines the primary structure
the order of nucleotides in a gene
what is the secondary structure
when hydrogen bonding between peptide bonds creates localised folding
what two structures can protein chains fold to
alpha helix, beta-plated sheet
where can the hydrogen bonds be found in protein folding
between the C=O and the H-N
name four types of amino R groups
-Ionic
-Cysteine (S)
-Hydrogen bonding (OH)
-Hydrophobic interactions (CH3)
what bonds do Cysteine R groups form and whats its name
Strong covalent bonds, called a disulphide bridge
what is tertiary structure
the precise 3D shape of a single polypeptide, stabilised by R-group interactions
name four examples of R-group interactions
hydrogen bonding, disulphide links, ionic interactions, hydrophobic interactions
whats another name for 3D shape
tertiary
define the quaternary structure
more than one polypeptide chain associating to form the final protein structure
how to test for proteins
add biuret reagent I (dilute copper sulfate solution) and biuret reagent II (dilute sodium hydroxide solution) to the sample. positive result will go from light blue-purple
describe a disulphide bond
strong covalent bonds between the r group of 2 cysteine amino acids
