BIOLOGY NOTES. CHAPTER 5 : BIOCATALYSIS SUBTOPIC : 5.1 Properties of enzymes and mechanism of actions

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1 BIOLOGY CHAPTER 5 : BIOCATALYSIS SUBTOPIC : 5.1 Properties of enzymes and mechanism of actions LEARNING OUTCOMES: a) State the properties of enzymes. b) State the six classes of enzyme according to IUB classification.. MAIN IDEAS Enzymes An organic catalyst (usually a protein) that speed up/accelerates a specific chemical reaction by required for that reactions without itself being affected by the reaction Properties of enzymes 1. Required Only in Small Amount. 2. They are not altered irreversibly during the course of reaction They have no effect on the thermodynamics of the reaction. 5. Denatured by high and. 6. Speed up the chemical reactions Classification of enzymes A systematic nomenclature for enzymes was recommended by the International Union of Biochemistry (IUB). Each enzymes was allocated a trivial name: o The name of the substrate act upon the enzyme o The type of reaction catalysed o The suffix ase o E.g: urase, sucrase, protease. Enzyme Group Type of reaction catalyzed Enzyme examples 1.Oxidoreductase Transfer of O and H atoms between substances. All oxidation- 1 KMPk

2 reduction reactions. 2. Transferase 3. Hydrolase Hydrolysis reactions 4. Lyases 5. Isomerase Catalyse geometric or structural rearrangement within one molecule 6. Ligase 2 KMPk

3 BIOLOGY CHAPTER 5 : BIOCATALYSIS SUBTOPIC : 5.1 Properties of enzymes and mechanism of actions LEARNING OUTCOMES: a) Explain the mechanism of enzyme action (lowering activation energy) b)describe the hypotheses related to its mechanism of action: Induced Fit Model Lock and Key Model. MAIN IDEAS Activation energy The initial energy needed to start a chemical reaction is called the free energy of activation, or activation energy (E A). Activation energy is often supplied in the form of heat from the surroundings How do enzymes works Lowering the barrier necessary to initiate a chemical reaction Mechanism of enzymes action. The reactant that an enzyme acts on is called the enzyme s substrate. The is the region on the enzyme where the substrate binds. In an enzymatic reaction, the substrate binds to the active site of the enzyme Forming an enzyme-substrate complex. 3 KMPk

4 Catalysis in the Enzyme s Active Site In an enzymatic reaction, the substrate binds to the active site of the enzyme. The active site can lower an E A barrier by : o Orienting substrates correctly o substrate bonds o Providing a o Covalently bonding to the substrate Mechanism of enzyme action Two Hypotheses: i. Lock and Key Model ii. Model Lock and Key Model Lock :Enzyme (active site) Key :. Substrate s molecule (key) shape is complementary with active site of the enzyme molecule (lock). Substrate fits accurately into a rigid active site of the enzyme molecule. Forming. Then the product is form. Product no longer fit into the active site. Leave the active site free to receive further substrate molecule Induce Fit Model Active site (enzyme) is able to to enfold a substrate molecule. 4 KMPk

5 Distorted enzyme molecule in turn distorts the substrate molecule. Straining or twisting the bonds. Substrates less stable and thus lowering EA. Products are formed which no longer bind to active site and so move away. Enzyme returns to its. Ready to bind the next substrate molecule. BIOLOGY CHAPTER 5 : BIOCATALYSIS SUBTOPIC : 5.1 Properties of enzymes and mechanism of actions 5.2 Cofactors LEARNING OUTCOMES: a) Explain Factors That Affect The Enzymatic Reaction. b) Explain The Types and Functions of Cofactors.. MAIN IDEAS Factors that affect the enzymes reactions The rate of an enzyme-catalyzed reaction is affected by : Chemical and Physical Factor that alters the enzyme s 3- D shape : Temperature Concentration of and enzyme. 5 KMPk

6 Effect of temperature Each enzyme has an at which an enzyme produces the highest production rate. Optimal conditions favor the most active shape for the enzyme. Effects the movement of enzyme. Increase temperature : The rate of an enzymatic reactions will. Substrates with active sites more frequently. Fastest conversion of the reactants to product molecules. Above optimal temperature:enzymes. Rate of reactions drop sharply Effect of ph Different enzymes, different optimum ph. Example : and Enzymes prefer to work at an optimum ph. Outside of its ph range the enzyme is. 6 KMPk

7 Effect of substrate concentration The amount of substrate will affect the rate of reaction. Substrate concentration increases, rate of reaction will. Then it will. All the enzyme molecules (active sites) are occupied At low enzyme concentration and the rate of reaction is. Cofactors One or more components required by enzymes in order to function efficeintly. Atom or molecules that are not part of the enzyme s primary structure. Types of cofactor There are three types of cofactors : No Cofactors Examples 1. Metal Ions/Activator (Inorganic) 7 KMPk

8 2. vitamin 3. Prosthetic group Metal ion Non-protein inorganic substances. Assist in forming ES complex by either enzyme or substrate molecule into more suitable shape. Coenzymes Non-protein organic or organometallic substances. or bound to the enzyme. Most vitamins act as coenzymes or raw material from which coenzymes are made. Prosthetic group A metal or Coenzymes that are or bound very tightly to their enzyme. E.g: prosthetic group of electron carrier cytochrome and enzyme catalase. FAD (riboflavin) - prosthetic group of the electron carrier cytochrome. It take part in oxidation-reduction reactions Functions of cofactors Assist in forming the enzyme-substrate complex by altering the into a more suitable shape. May function to withdraw from the substrate. May involve in transfer of electrons / atoms / chemical groups in enzyme reactions BIOLOGY CHAPTER 5: BIOCATALYSIS 8 KMPk

9 SUBTOPIC : 5.3 Inhibition LEARNING OUTCOMES: Explain the roles and types of inhibitors. Explain reversible inhibition: competitive and non competitive inhibitors. Explain irreversible inhibition.. MAIN IDEAS Inhibitors A substance that binds to an enzyme and decreases its activity.. Types of inhibitors There are TWO types of inhibitor : 1.Reversible Competitive inhibitor 2. Irreversible Competitive inhibitor Has close structural to the normal substrate. Inhibitor & substrate for active site. Bind reversibly to the active site (loosely bind). Effect is to the enzyme. Enzyme can be reused again (do not destroy and do not denatured). Causes No to the enzyme Non competitive Shape of inhibitor is to the shape of substrate. Inhibitor will DO NOT directly compete with the substrate to bind to the enzyme at the active site. 9 KMPk

10 Inhibitor binds to site other than active site which is site (Regulatory site) Allosteric inhibitor o regulation of enzyme function o keeps enzyme inactive. When the inhibitor is present it fits into its site. Causes enzyme (active site) to change shape.(conformational change). The substrate bind with the substrate. Examples of Non competitive end product inhibition Negative feedback : End point or Example: Synthesis of amino acid, 10 KMPk

11 o isoleucine from amino acid. Irreversible Inhibition Inhibitor or irreversibly to : o active site of enzyme. o allosteric site of enzyme. Often form a to an amino acid residue at or near the active site. Example: 1. Cyanide 2. Nerve gases and pesticide Cyanide irreversibly inhibits activity of (in cellular respiration). Blocks transfer of electrons from substrate to & 11 KMPk

12 death may occur. BIOLOGY DIAGRAM 1. Complete the label in the diagrame. 12 KMPk

13 Course of reaction without enzyme Free Reactants energy Course of reaction with enzyme Progress of the reaction G is unaffected by enzyme Products 2. Label the diagram the correct answers. Enzyme 13 KMPk

14 3. Complete the diagram 4. Complete the mechanism of enzymes actions 14 KMPk

15 5. Factors that affect the enzymatic reaction. 6. Name the structure label A. 15 KMPk

16 A 7. Describe the effect of substrate based on the graph V max Reaction velocity Substrate concentration 8. Label the structure in the diagram. 16 KMPk

17 9. Identify the types of inhibitor based on the diagram 10. Describe the non competitive inhibitor based on the diagram. 17 KMPk