1. Lesson 13

2.  State that enzymes are globular proteins with a specific tertiary structure  State that enzymes catalyse metabolic reactions  State that enzyme action may be extracellular or intracellular  State that enzymes catalyse metabolic reactions  Describe the mechanism of enzyme action  Explain what is meant by enzyme-substrate complex and enzyme-product complex  Describe how enzymes lower activation energy  Explain the importance of coenzymes and cofactors in enzyme controlled reactions

3.  Enzymes are globular proteins with a specific tertiary structure  Enzyme action may be intracellular or extracellular  Enzymes are biological catalysts  Enzymes catalyse metabolic reactions  Enzymes lower activation energy because of the way the active site is shaped to fit the substrate

4.  Use the plasticene to model the lock and key model of enzyme action

5.  They are proteins of high molecular weight  They are biological catalysts  They are sensitive to temperature changes being denatured at high temperatures  They are sensitive to pH  They are generally specific in the reactions they catalyse  Enzymes possess an active site within which chemical reactions take place Substrate molecule in the ACTIVE SITE Enzyme molecule

6. The Lock And Key Model In an enzyme - catalysed reaction, the enzyme binds to the substrate to form a complex An enzyme - substrate complex forms A reaction occurs forming an enzyme - product complex Products diffuse away from the active site Enzyme molecule The lock & key model proposes that the substrate binds to the active site which it fits exactly, like a key in a lock S

7. The Induced Fit Model This model takes into account the fact that proteins (enzymes) have some three-dimensional flexibility SUBSTRATE Substrate binds to the enzyme at the active site Binding of the substrate induces the enzyme to change shape such that there is an exact fit once the substrate has bound Enzyme Molecule According to this model, reactions can only take place AFTER induced fit has occurred

8.  Read page 127 in the text book  Create a comparison table for lock and key and induced fit hypothesis Lock and Key ModelInduced Fit Hypothesis

9.  Specificity,  The active site of an enzyme is a specific shape, depending on the reaction that it catalyses, meaning that other molecules won’t fit into the active site  Active site,  The area on an enzyme to which the substrate binds  Lock and key hypothesis,  The theory of enzyme action in which the enzyme active site is complementary to the substrate molecule, like a lock and key  Induced-fit hypothesis,  The theory of enzyme action in which the enzyme molecule changes shape to fit the substrate molecule more closely as it binds to it  Enzyme-substrate complex,  The intermediary formed when a substrate molecule binds to an enzyme molecule  Enzyme-product complex  The intermediate structure in which product molecules are bound to an enzyme molecule lowering of activation energy

10.  Answer the following question  Describe the mechanism of enzyme action  Use as many key terms as possible  Person with the most key terms used correctly wins a prize

11.  Swap answers  Highlight all the key terms in their response  Enzyme  Substrate  Enzyme substrate complex  Enzyme product complex  Product  Collision  Active site  Lock and key  Induced fit  Maximum mark of 9, lose a mark for every incorrectly used term or missed term

12.  Cofactor: substance that must be present for enzyme controlled reactions to take place at the appropriate rate  Coenzyme: organic molecule that binds either just before or at the same time as the substrate (help reactions take place in sequence)  Prosthetic group: inorganic ion that is a permanent part of the enzyme contributing to its 3D shape  Inorganic ions: either bind to enzyme or substrate to help form the enzyme substrate complex

13.  Role play, model or draw the effect of coenzymes and cofactors in enzyme controlled reactions

14.  State that enzymes are globular proteins with a specific tertiary structure  State that enzymes catalyse metabolic reactions  State that enzyme action may be extracellular or intracellular  State that enzymes catalyse metabolic reactions  Describe the mechanism of enzyme action  Explain what is meant by enzyme-substrate complex and enzyme-product complex  Describe how enzymes lower activation energy  Explain the importance of coenzymes and cofactors in enzyme controlled reactions

15.  One form of COPD develops because enzymes are released by phagocytes entering the alveoli. This enzyme action can break down elastin in the lining of the bronchioles and alveoli. Use the example of elastin breakdown to explain the induced-fit hypothesis of enzyme action [5]

16.  elastin is substrate  (elastin / substrate) binds to / fits into, active site ;  active site / enzyme / elastase / substrate / elastin, shape changes  idea of closer fit (between active site and substrate)  more bonds form (between substrate and active site)  forms enzyme-substrate-complex / ESC  idea that (change in shape of active site) destabilises / weakens, bonds (in substrate) / substrate  activation energy reduced  idea of further shape change of, active site / enzyme, after products form

17.  Make a glossary of key enzyme terms