1. Enzymes

2. Speed in chemical reactions can be very important. Think of what would happen if the food you just ate takes 3 days to digest. Speed in chemical reactions can be very important. Think of what would happen if the food you just ate takes 3 days to digest.

3. There are chemicals (or substances) that can change the speed of chemical reactions. These are known as catalysts. Catalysts lower the activation energy (how much energy it takes for a reaction to occur) There are chemicals (or substances) that can change the speed of chemical reactions. These are known as catalysts. Catalysts lower the activation energy (how much energy it takes for a reaction to occur)

4. Enzymes are biological catalysts that change the speed of chemical reactions without themselves being changed at the end of the reaction. Enzymes are biological catalysts that change the speed of chemical reactions without themselves being changed at the end of the reaction.

5. Properties of Enzymes: Enzymes are proteins. Enzymes are proteins. They speed up chemical reactions inside cells. They speed up chemical reactions inside cells. They are needed only in small amounts. They remain unchanged after each reaction and can therefore be reused. They are needed only in small amounts. They remain unchanged after each reaction and can therefore be reused. Each enzyme can only work on ONLY ONE substrate. For example, lactase will only work on lactose found in milk They are highly specific. Each enzyme can only work on ONLY ONE substrate. For example, lactase will only work on lactose found in milk They are highly specific.

6. How enzymes work lock and key model

7. Effect of temp. on enzymes At very low temperatures, enzymes are inactive. At very low temperatures, enzymes are inactive. The activity of enzymes increases when the temperature increases (and therefore the reactions that they work on, or catalyze, will also become faster) The activity of enzymes increases when the temperature increases (and therefore the reactions that they work on, or catalyze, will also become faster) Each enzyme has a special temperature that they are most active. This is the optimum temperature for that enzyme. Each enzyme has it’s own optimum temperature. Each enzyme has a special temperature that they are most active. This is the optimum temperature for that enzyme. Each enzyme has it’s own optimum temperature. When the temperature is too high, the enzymes are destroyed, or denatured When the temperature is too high, the enzymes are destroyed, or denatured

8. Optimum Temp. Graph

9. pH effects enzymes Different enzymes work best at different pH. The pH that makes the enzyme most active is known as the optimum pH. Different enzymes work best at different pH. The pH that makes the enzyme most active is known as the optimum pH. If the pH is very high (a base) or very low (an acid), enzymes can be denatured. If the pH is very high (a base) or very low (an acid), enzymes can be denatured. Therefore, how fast the enzyme can catalyze depends on factors like temperature or pH. Therefore, how fast the enzyme can catalyze depends on factors like temperature or pH.

10. Optimum pH graph

11. Look at this graph Which enzyme would you expect to find in a hot spring? Which enzyme would you expect to find in a hot spring? Which enzyme has an optimum temperature of 40°C? What is the optimal temp of the other one? Which enzyme has an optimum temperature of 40°C? What is the optimal temp of the other one? At what temp. do the two enzymes have the same amount of activity? At what temp. do the two enzymes have the same amount of activity?