proteins Flashcards
(20 cards)
the elements that are present in amino acids and proteins
Nitrogen, carbon, hydrogen, oxygen and some times sulfur
example of a role of a protein
haemoglobin transports oxygen around in the blood
what are the monomers which form proteins called
amino acids
what does the ‘R’ represent in the display formula of an amino acid
a carbon containing side chain
where do amino acids differ
in their side chain
what bond forms between two amino acids in a condensation reaction
peptide bond
other than the bond what forms by the condensation of two amino acids
a dipeptide
what parts of the amino acids react during a condensation reaction to form a dipeptide
the OH/hydroxyl group from one amino acid reacts with the hydrogen from the amine group of another to form the water molecule.
how are polypeptides formed
the condensation of many amino acids.
what is at each end of a peptide chain.
an amine group at one end and a carboxyl group at the other end.
four levels of organisation of proteins structure
primary, secondary,tertiary, Quaternary
describe the primary structure of a protein.
the sequence of amino acids in a polypeptide chain.
describe the secondary structure of a protein.
the folding of a polypeptide into an alpha helix or beta pleated sheet.
how is the structure maintained in the secondary structure of proteins.
hydrogen bonds between between the NH group of one amino acid and the c=o group of another.
describe the tertiary structure of a protein.
the further folding of the polypeptide chain into a specific 3D complex shape.
what determines how the polypeptide is folded in the tertiary structure of a protein.
the R group and the shape is held together between the R groups in different amino acids.
three types of bonds between the R groups
Hydrogen bonds
ionic bonds- from between oppositely charged R groups
Disulphide bridges - covalent bonds which form between sulphur containing side chains.
Why is the tertiary structure so important
the shape it forms determines how it reacts with other molecules e.g. active sites in enzymes
what is quaternary protein structure
the structure of proteins which contains two or more polypeptide chains joined together.
what is the chemical test for the presence of proteins
the biuret test - add biuret solution to the sample.
if the protein is present there will be a colour change from blue to lilac . If not present there will be no colour change.
