Topic_C_Enzymes_H1H2_2015

NANYANG JUNIOR COLLEGE H1 / H2 Biology Enzymes J1/2015 1 TOPIC C: ENZYMES Learning Outcomes Core Topic 1: Cellular Functions Candidates should be able to: (h) Explain the mode of action of enzymes in terms of an active site, enzyme/ substrate complex, lowering of activation energy and enzyme specificity. (i) Follow the time course of an enzyme -catalysed reaction by measuring rates of formation of products (e.g. using catalase) or rate of disappearance of substrate (e.g. using amylase). (j) Investigate and explain the effects of temperature, pH, enzyme concentration and substrate concentration on the rate of enzyme catalysed reactions, and explain these effects. (k) Explain the effects of competitive and non -competitive inhibitors (including allosteric inhibitors) on the rate of enzyme activity. Content Outline 1. Introduction 2. Characteristics of Enzymes (a) Common Properties of Enzymes 3. Mode of Action of Enzymes (a) Active Site (b) Enzyme specificity (c) Enzyme-Substrate Complex (d) Activation Energy 4. Enzyme Kinetics (a) Measurement of Enzyme Kinetics (b) Measurement of Enzyme Affinitiy 5. Factors Affecting Enzyme Activity (a) Substrate Concentration (b) Enzyme Concentration (c) Temperature (d) pH 6. Enzyme Inhibition (a) Competitive Inhibition (b) Non-competitive Inhibition (c) Reversible Inhibition (d) Irreversible Inhibition

NANYANG JUNIOR COLLEGE H1 / H2 Biology Enzymes J1/2015 2 References 1. Boyle, M. and Senior, K. (200 2) Biology. Chapter 5: Enzymes and Metabolism . Harper Collins Publishers Limited. 2. Campbell, N. A. and Reece J.B. (2008) Biology. Chapter 8: An Introduction to Metabolism . Eighth Edition. Pearson Education, Inc. 3. Jones, M. and Jones, G. (2004) Advanced Biology. Chapter 2 : Enzymes . Cambridge University Press. 1. Introduction Enzymes catalyse biological reactions. Thus, they are also called biological catalyst s. Most biological catalysts are globular proteins. However, some enzymes are RNA molecules known as ribozymes. For example, peptidyl transferase activity found in ribosome is mediated by the ribosomal RNA in the large subunit. They are important as many metabolic reactions, though spontaneous, occur at a very slow rate. Thus, enzymes are needed to speed up the se reactions. They are involved in almost all biochemical reactions in living organisms including respiration, photosynthesis, digestion and biosynthesis of macromolecules. Enzymes are usually classified according to the type of reaction they catalyse and they can be named according to their substrates (i.e. reactants that enzymes act on). Classification of Enzymes Class of Enzyme Type of Reaction Catalysed Examples Oxidoreductase Transfers electrons, oxygen atom or hydrogen atom between molecules, i.e. oxidation-reduction reactions Dehydrogenases Oxidases Transferase Transfers a functional group from one molecule to another molecule e.g. phosphate group Kin