Proteins 1A Flashcards
What are proteins made from
long chains of amino acids
How is a dipeptide formed
when two amino acids are joined together
what is the monomer that proteins are made from
amino acids
How is a polypeptide formed
when more than two amino acids are joined together
What chains are proteins made from
one or more polypeptide chains
General structure of an amino acid
a carboxyl group, an amine or amino group and a variable group
How many different amino acids are there
20
How are amino acids joined together
Via condensation reactions to form polypeptides
How do amino acids vary
By R groups
What are the bonds between amino acids called
peptide bonds
What is the primary structure of a protein
the sequence of amino acids in the polypeptide chain
What is the secondary structure of a protein
Hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet
What is the tertiary structure of a protein
the coiled or folded chain of amino acids is often folded or coiled further more bonds are formed between different parts of the polypeptide chain including hydrogen bonds and ionic bonds. Disulphide bridges also form whenever two molecules of the amino acid cysteine come close together the sulphur atom in one cysteine bonds to the sulphur atom of another. For proteins made of a single polypeptide chain the tertiary structure forms their final 3D shape.
What is the quaternary structure of a protein
Some proteins are made of several polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together. For proteins which are made up of several polypeptide chains the quaternary structure forms the proteins final structure
Functions of enzymes
Enzymes: spherical due to the tight folding of the polypeptide chains. Soluble and often have roles in metabolism and others synthesise large molecules
Functions of antibodies
Antibodies: involved in immune response. They’re made up of two light (short) polypeptide chains and two heavy (long) polypeptide chains together. Antibodies also have variable regions the amino acid sequences in these regions vary
Functions of structural proteins
Physically strong, consist of long polypeptide chains lying parallel to each other with cross links between them. Eg keratin and collagen
Functions of transport proteins
eg channel proteins, contain hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel . These proteins transport molecules and ions across membranes
Test for proteins
Biuret test:
First add sodium hydroxide solution to the sample to make it alkaline, then add some copper (ii) solution if protein is present then the solution should turn purple if protein is not present then the sample will remain blue
