Proteins

Formula of amino acids

• NH2

• Variable group / R group

• COOH group

Why are amino acids buffers?

They reduce damages in pH

Name of reaction and the bond that forms a dipeptide

• Condensation reaction

• Peptide bond

Primary structure of a protein

The order of amino acids in a polypeptide

Secondary structure of a protein

The shape it forms because of H bonds forming between the amino group of one monomer & the carboxyl group of another monomer

2 types of secondary structure

• α helices

• β pleated sheets

Example of a protein with an α helix shape

Keratin

Example of a protein with a β pleated sheet shape

Silk

Tertiary structure of a protein

• Further folded in secondary structure

• More globular, compact & complex

• Specific 3 D shape due to properties of R group

• Metabolically active

4 examples of a tertiary structure protein

• Enzymes

• Hormones

• Immunoglobulins

• Albumins

Bond types in tertiary structure proteins, in order from weakest to strongest

• Hydrophobic interactions

• Hydrogen bonds

• Ionic interactions

• Disulphide linkages

Quaternary structure of a protein

• 2 or more types of polypeptides joined together by disulphide linkages

• Associated with non-protein groups as not many proteins reach this stage

Example of a molecule with a quaternary structure

Haemoglobin

Qualities of fibrous proteins

• Long thin parallel chains

• Insoluble

• Structural function

• Repetitive amino acid sequence

• Stable molecule as it’s linked by H bonds

Qualities of globular proteins

• Spherical 3D shape & compact

• Soluble to water

• Metabolic functions

• Irregular (not repetitive amino acid sequence)