Protein structure

What are the four atoms/groups of atoms bonded to the central carbon of an amino acid

What are the four atoms/groups of atoms bonded to the central carbon of an amino acid

• Amine group

• Carboxyl group

• Hydrogen atom (H)

• R group (fatty acid chain)

What is an amine group

NH2

What is a carboxyl group

COOH

What is an R group

Different in each amino acid

Determines how the amino acid bonds with others

How do amino acids bond together

Condensation reaction to form a peptide bond between the amine group of one amino acid and the carboxyl group of another

Functions of proteins

• Enzymes

• Antibodies

• Transport proteins → channel proteins

• Structural proteins → collagen, keratin

How do you test for protein presence

1. Add sample to biuret solution

2. Shake and leave upright for 5 mins

3. Colour change from blue to lilac if present

What is the primary structure of a protein

The order/sequence of the amino acids

→ determined by the gene coding the protein

What is the secondary structure of a protein

Coiling/folding of the polypeptide into an alpha helix or beta pleated sheet

→ hydrogen bonds form between amino acids in the chain, causing the protein to fold into specific structures

What is the tertiary structure of a protein

The 3D structure formed by an interaction between the R groups of each amino acid in the chain

What are the 4 types of bond that may be present in tertiary structure

• Hydrogen

• Ionic

• Disulphide bridge

• Hydrophobic interactions

How do ionic bonds form in tertiary structure

How do disulphide bridges form in tertiary structure

S-S bonds

What is the quaternary structure of a protein

Multiple polypeptides joining to form one protein

→ e.g. insulin, collagen, haemoglobin