Proteins

Amino acid

1. Monomer units that from protein

2. Has a certain carbon atom

3. Has amine group (NH2)

4. Has carboxyl group (COOH)

5. Has hydrogen atom (H)

6. Has R group (carbon chain) each different amino acid have different R groups

Peptide bond

1. Is a condensation reaction

2. COOH group from one amino acid, reacts with NH2 group of another amino acid, forming water and a peptide bond

Primary structure of proteins (Polypeptides)

1. Hundreds of amino acids join together to form a polypeptide

2. Sequence of amino acids in a polypeptide chain forms primary structure of a protein.

3. Determines shape and function

Secondary structure of proteins (Folding)

1. Polypeptide chain folds into a alpha helix or beta pleated sheet

2. This happens because there is a carboxyl group at one end of the polypeptide and a amine group at the other end

3. The H in amine has a delta positive charge

4. The O in carboxyl has a delta negative charge

5. This called a hydrogen bond, and causes attraction between the 2, causing polypeptide chain to fold

Tertiary structure of proteins (Further folding)

1. Polypeptide chain further folds into a 3D shape

2. This is stabilised by a number of different bonds, bonds occurring depends on primary structure of protein

3. Disulfide bridges (strong covalent bonds between cysteine amino acids containing sulfur

4. Ionic bonds (formed between charged R groups easily broken by pH changes)

5. Hydrogen bonds (numerous but weak, easily broken by high temps)

Quaternary structure of proteins (Joining of polypeptides)

1. More than 1 polypeptide chain joins together to form a functional protein

2. Some have non-protein prosthetic groups joined with the protein (e.g haemoglobin)