Proteins Flashcards
Polypeptides
Amino acids are the monomers that join together to form polymers called polypeptides (proteins).
Structure of proteins
Proteins are made up of amino acids.
Dipeptides are formed from the condensation of two amino acids.
Polypeptides are formed by the condensation of many amino acids
R group
The R group is different in each amino acid.
The R group determines how the amino acid interacts and bonds with other amino acids in the polypeptide.
How many different amino acids
20
Fours groups surrounding the central carbon atom in an amino acid
Amine group
Carbóxyl group
Hydrogen atom
R group
Function of protein (antibodies)
Antibodies are made up of polypeptide chains.
Antibodies are used in the immune response.
Antibodies are diverse proteins.
Each antibody has a different sequence of amino acids.
Transport proteins
Transport proteins include channel proteins.
transport molecules across the cell membrane.
transport molecules that are too large to diffuse freely or molecules that carry a charge.
Structural proteins
are long, strong polypeptide chains.
connected by cross-links that hold the chains parallel to each other.
E.g. Collagen and keratin.
Monomer
One amino acid
Dipeptide
Two amino acids
Polypeptide
More than two amino acids
Glycine
Exception contains no carbon only one hydrogen atom
Amino acids
Linked together by condensation reactions to form dipeptides and polypeptides. A molecule of water is released during the reaction. Bonds formed between amino acids are called peptide bonds .
Reverse reaction happens hydrolysis when dipeptides and polypeptides are broken down
Primary structure
This is the sequence of amino acids in the polypeptide chain
Secondary structure
Polypeptide chain doesn’t remain flat and straight. Hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into a alpha or beta pleated sheet
Tertiary structure
Coiled or folded chain is often folded or pleated more. More bonds form between different parts of the polypeptide chain including hydrogen and ionic bonds.
Disulfide bridges form whenever two molecules of the amino acid cysteine come close together - the sulphur atom in one cysteine bonds to the sulphur atom in the other
Quaternary structure
The way these polypeptide chains are assembled together
Biuret test for proteins
- Test solution needs to be alkaline so first add a few drops of sodium hydroxide solution
- Then add some copper sulfate solution
If protein is present the solution turns purple if there is none it stays blue
