Quick test What is the definition of a catalyst? What type of molecule is an enzyme? What is the active site? What is the name of the substance that binds at the active site? What is a synthesis reaction? What does specificity mean in the context of enzymes? What type of enzyme breaks down proteins? Name one process in the body that relies on enzymes

Starter questions on enzymes   Starter questions on enzymes  Enzymes _______ up the rate of chemical ________. Enzymes are ________ because they only work on one substrate. The substrate fits into the ________ site of the surface of the _______. Enzymes can be re-used, so only _______ amounts are needed. To which group of chemical compounds do enzymes belong? _________ Why is an enzyme specific for a particular substrate? _________________________________________ Why can an enzyme be used again and again? _________________________________________

Starter questions on enzymes   Starter questions on enzymes  Enzymes speed up the rate of chemical reaction Enzymes are specific because they only work on one substrate. The substrate fits into the active site of the surface of the enzyme Enzymes can be re-used, so only small amounts are needed. To which group of chemical compounds do enzymes belong? Proteins Why is an enzyme specific for a particular substrate? The active site of the enzyme is complementary to one type of substrate only. Why can an enzyme be used again and again? They are catalysts which means that they allow the reaction to happen at a faster rate, without being used up or changed themselves.

Factors affecting enzyme action Learning objectives Describe and explain the effect of temperature and pH on the rate of enzyme catalysed reactions Understand that denaturation results in a change to the active site.

Exam technique DESCRIBE – what does it look like? Imagine someone can’t see the graph/table. Give enough detail so that they can picture exactly what the pattern is. EXPLAIN – why does it look like that? Use scientific knowledge to account for the pattern described.

Describe how the rate of reaction of an enzyme reaction changes at different temperatures (always include data) Optimum temperature Rate Of Reaction 0 10 20 30 40 50 60 70 Temperature/oC

Describe As the temperature increases the rate of reaction increases from 0oC to 40oC. The optimum temperature (peak rate of reaction) is at 40oC. As the temperature increases beyond 40oC, the rate of reaction decreases. (More rapidly than the increase in rate to 40oC). The rate of reaction reaches 0 at 60oC

Explain why the rate of reaction of an enzyme reaction changes at different temperatures Optimum temperature Enzyme molecules are denaturing Molecules gain kinetic energy Rate Of Reaction All enzyme molecules are denatured 0 10 20 30 40 50 60 70 Temperature/oC

Explain why the rate of reaction of an enzyme reaction changes at different temperatures 0-40oC An increase in temperature increases the kinetic energy of the enzyme and substrate molecules. The molecules move about faster and result in an increase in collisions resulting in the formation of enzyme-substrate complexes. Collisions are more frequent and energetic. >40oC High temperatures cause the amino acid chains to alter, which distorts the shape of the active site. The substrate can no longer fit at the active site – it has been denatured. The enzyme is no longer able to catalyse the reaction. In humans the optimum temperature for enzymes is 37oC

Explain Optimum temperature Rate Of Reaction Temperature/oC Enzyme molecules are denaturing Molecules gain kinetic energy Rate Of Reaction All enzyme molecules are denatured 0 10 20 30 40 50 60 70 Temperature/oC

Effects of pH on enzyme action

The activity of enzymes is also affected by pH Enzymes work best at an optimum pH. The pH change alters the forces that hold the amino acid chains in place at the active site. Outside of its pH range the enzyme is denatured. Optimum pH pepsin amylase Rate Of Reaction 1 2 3 4 5 6 7 8 9 10 11 12 pH

Denaturing A change to the 3D shape of the active site of the enzyme caused by high temperatures or a change in pH. The enzyme no longer works as a catalyst. The damage can sometimes be irreversible The enzyme has NOT died….it was never alive!

Substrate Substrate Complementary active site Active site changed Enzyme Enzyme is denatured

Describe and explain the effect of temperature on the rate of the enzyme controlled reaction Include these key words in your answer…. Denatured Optimum temperature Active site Kinetic energy Substrate Reaction Collision Enzyme-substrate complex Frequent Energetic Amino acid

Examples of enzymes in your body… Use Protease (in the stomach) Breaking down proteins Amylase (in the mouth) Breaking down carbohydrates Lipase (in the intestines) Breaking down fats Catalase (in the liver) Breaks down hydrogen peroxide

respiration rate shape chain amino acid reactant amylase specificity Write a scientific clue/definition for the words below. There can only be 1 correct ‘splat’ to your question. respiration rate shape chain amino acid reactant amylase specificity protease lock & key biological enzyme product protein reaction synthesis catalyst active site substrate

Practical next lesson…… To investigate the effects of temperature on the activity of pectinase in forming apple juice. (Pectinase degrades pectin in the apples so that juice is produced more readily) Plan a practical Include a step by step method Identify the independent, dependent and control variables Safety points