Lesson 5

 Explain the term secondary structure  Explain the term tertiary structure

 Draw the structure of a protein and label it in as much detail as you can

 The coiling and pleating of parts of the polypeptide molecule

 Alpha Helix or Beta Pleated Sheet  Hydrogen bonds hold the structure in place  Hydrogen bonds form between oxygen and hydrogen atoms  Although hydrogen bonds are quite weak, as many bonds are formed they add stability to the structure of the protein

 Right hand coil, where hydrogen bonds form between oxygen and hydrogen atoms bought into close proximity  Stabilises the protein Alpha helix HYDROGEN BOND

 Amino acid chain folds up on itself forming anti- parallel chains  O and H atoms bought in close proximity to each other form hydrogen bonds  Stabilises the protein Beta pleated sheet

 Make plasticene models of alpha helix and beta pleated sheet  Describe the structures to the person next to you

 The overall 3D structure of the protein molecule

 The final 3D shape of the protein is formed when the polypeptide chain with the coils and pleats fold themselves  The 3D shape is held in place by  Hydrophobic and hydrophilic interactions  Disulphide bonds  Ionic interactions

Primary Secondary Tertiary Quaternary

 In groups of 4 each person gets a quarter of an OHT to explain one of the following:  Tertiary structure  Hydrophobic and hydrophilic interactions  Disulfide bonds  Ionic interactions  You will then present to the class

 Many hydrophobic R groups tend to cluster towards the interior of the protein molecule forming Hydrophobic Interactions  Hydrophilic R Groups tend to be found on the outside of proteins

 R groups of two amino acids contain sulphur atoms (e.g. cysteine)  If these atoms are in close proximity they form DISULPHIDE BONDS

 Many of the carboxylic acid and amino groups form charged groups in solution. Oppositely charged groups form IONIC BONDS

 The proteins shape is vital to each function  Three examples are  Enzyme  Hormone Receptor  Collagen  Why is shape important in these three cases?

 Enzyme: fit of the active site to its specific substrate  Hormone receptor: hormone won’t bind unless specific shape  Collagen: shaped for strength

 Globular  Ball structure  Hydrophobic amino acids turn inwards and hydrophilic interactions turn outwards making them water soluble  E.g. enzymes  Fibrous  Form fibres  Regular repetitive amino acid sequences  Usually insoluble  E.g. collagen

 Explain the term secondary structure  Explain the term tertiary structure

 Draw the structure of a protein and label it in as much detail as you can

 Complete the next part of the summary table