Proteins

1. Proteins

2. Assumed Knowledge • Amino acid structures and properties • Secondary structure (α-helix and β-sheet). • Protein synthesis occurs on ribosomes (cytoplasm) – covered in the genetics presentation • Functions of proteins

3. Amino Acids Amino acids are the building blocks of proteins There are 20 amino acids found in proteins All have a standard structure

4. Properties • Size – small, bulky, affects the folding of a protein • Charge • H – bonding • Disulphide bonding between two cysteine amino acids

5. Protein Structure • Primary structure – the sequence of amino acids (the polypeptide chain) • Secondary structure – folding into an α-helix or a β-sheet • Tertiary structure – further folding of the protein • Quaternary structure – association of multiple proteins to form a multi-subunit protein

6. Peptide bond – bonds between the amino group and the carboxyl groups of amino acids. The bonds form with the loss of water - dehydration reaction

7. α-helix - right handed coil structure with precise spacing throughout β-sheet – a lateral connection of β-strands (stretches of amino acids)

8. Collagen – most abundant protein Made of three left handed helices arranged in a right-handed super helix

9. Protein Function • Enzymes- kinase • Transport - haemoglobin and myoglobin (O2) • Storage - haemoglobin • Motility - actin and myosin. • Structure – collagen • Defence - immunoglobulins (antibodies). • Communication - Signals (insulin) and receptors (insulin receptor) • Gene control- transcription factors