Enzymes

1. Enzymes Noadswood Science, 2012

2. Enzymes & pH • To investigate the effect of pH on enzymes

3. Digestive System

4. Enzymes • What are enzymes? • Enzymes are biological catalysts - catalysts are substances that increase the rate of chemical reactions without being used up • Enzymes are specifically proteins that are folded into complex shapes that allow smaller molecules to fit into them – the place where these substrate molecules fit is called the active site

5. Enzymes • If the shape of the enzyme changes, its active site may no longer work – the enzyme has been denatured • They can be denatured by high temperatures or extremes of pH • *It is wrong to say the enzyme has been killed – although enzymes are made by living things, they are proteins, and not alive

6. Life In Cold Blood • How does temperature affect feeding – consider cold and warm blooded animals… • As the temperature increases, so does the rate of reaction • The enzyme activity gradually increases with temperature until around 37°C

7. Enzymes & pH • Changes in pH alter an enzyme’s shape • Different enzymes work best at different pH values – the optimum pH for an enzyme depends on where it normally works • E.g. intestinal enzymes have an optimum pH of about 7.5 and enzymes in the stomach have an optimum pH of about 2

8. Trypsin & pH • Trypsin is an enzyme which breaks down protein • If Trypsin is added to milk it will break down the milk, turning it from cloudy to translucent • You need to carry out an experiment to find out how the pH of the medium affects how quickly the Tryspin breaks down the milk • You will have 3 boiling tubes of milk (in different pH conditions) • To each you will add some Tryspin • You need to time how long the solution went from being cloudy to translucent

9. Trypsin & pH • Take 3 boiling tubes, and fill them each with 10ml of milk – place them in a rack • To each boiling tube add 20ml of a different pH solution (acidic, neutral and alkaline) • Add 10ml of Trypsin to each boiling and begin the timer – time how long it takes for the solution to become transparent for each test • Record all your results

10. Quiz