1. Homework 1.Make a table to contrast the features of fibrous and globular proteins (see next slide) 2.Worksheet protein structure and carbohydrate questions 3.Complete question sheet from todays practical

2. Protease practical

3. Proteins - Fibrous v globular FibrousGlobular Shape Structure Solubility Stability Function Examples

4. Proteins - Fibrous v globular FibrousGlobular Shape Long chainsBall Structure Tightly wound secondary structure, tertiary twisted again quaternary multi chains loop around each other Secondary usually a mixture of alpha helix and beta sheet, tertiary wound into a globular shape, can be quaternary structure Solubility Insoluble – chains are h bonded to each other so few exposed groups to interact with water molecules More soluble – forms a colloid – interactions between hydrophillic R groups and water Stability So many h bonds that it takes a lot to disrupt the structure. Stable Easily disrupted – denatured Less bonds holding it together Function Structural e.g. hair etc.Metabolism (chemical reactions in cells) Examples Collagen – tendons Keratin hair Haemoglobin, antibodies Enzymes, some hormones

5. pH2 pH4 pH10 pH8 pH6 pH7 Fastest = pH7 Next = pH6 3 rd = pH10 4 th = pH8 5 th =pH4 Denatured = pH2

6. Results pHTime taken for solution to clear/m Rate = 1/time In m -1 10 8 7 6 4 2

7. Graph Independent variable on the x axis = Dependent variable on y axis =

8. Worksheet questions 1.Remember the change in absorbance takes place because the enzyme is digesting the protein in the milk powder solution. What is happening in the cuvette at pH7? Use the words protein, amino acids, soluble, insoluble, hydrolysis, enzyme =protease (neutrase) in your answer. (3 marks) 2.Which is the optimum pH for neutrase? (1 mark) What is the evidence from the data for this?(1 mark) 3.The textbook value for optimum pH for neutrase is 5.5-7.5. Do your results agree with this? (1 mark) 4.Why is using the colorimeter better than just taking the time the milk takes to clear by eye for each pH?(1 mark) 5.Can you criticise any of the plot lines (e.g. are they all smooth)? (1 mark) 6.Why may these anomalies have occurred? (2 marks) 7.How could you make the experiment more reliable? (3 marks) 8.Why did we use buffer solutions? (1)