YIJC [H2] CI1.3 Enzymes (N)

2024 JC1 H2 Biology Lecture Notes 1 CORE IDEA 1: THE CELL AND BIOMOLECULES OF LIFE TOPIC 1.3: ENZYMES Learning Outcomes: (p) Explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity using lock -and-key and induced -fit hypotheses. (q) Investigate and explain the effects of temperature, pH, enzyme concentration and substrate concentration of an enzyme-catalysed reaction by measuring rates of formation of products (e.g. measuring gas produced using catalase) or rate of disappearance of substrate (e.g. using amylase, starch and iodine). (r) Describe the structure of competitive and non-competitive inhibitors with reference to the binding sites of the inhibitors. (s) Explain the effects of competitive and non-competitive inhibitors (including allosteric inhibitors) on the rate of enzyme activity. References Campbell, Urry, Cain, Wasserman, Min orsky, Reece (2018) Biology – A Global Approach (11 th Edition)(Global Edition) Chapter 6: Energy and Life pg. 151 – 161 (Pearson Publication) ISBN- 10 1-292-17043-3 Lecture Outline: 1 Introduction 2 Properties of Enzymes 3 Mode of Action of Enzymes 4 Enzyme Kinetics 5 Factors Affecting Enzyme Activity 6 Enzyme Inhibition 7 Allosteric Regulation H2

2 1 INTRODUCTION Enzymes are biological catalysts which speed up the rate of metabolic reactions while remaining unchanged at the end of the reaction. Metabolic reactions are spontaneous (can occur without enzymes) but they occur at a very slow rate. Thus, enzymes are needed to speed up the se reactions. They are involved i n almost all biochemical reactions in living organisms including respiration, photosynthesis, digestion and biosynthesis of macromolecules. Fig. 1.1: Overview of metabolic reactions in a generalised animal cell Metabolic reactions can be classified into catabolic and anabolic reactions: Anabolic Reactions Catabolic Reactions Synthesis of complex molecules from simpler molecules Breakdown of complex molecules into simpler molecules Energy required Energy released E.g. Formation of glycogen from glucose, catalysed by glycogen synthase E.g. Breakdown of sucrose to glucose and fructose, catalysed by sucrase (a) Anabolic reaction via condensation (b) Catabolic reaction via hydrolysis Fig. 1.2: Anabolic and catabolic reactions

3 DID YOU KNOW? Not all enzymes are pro tein in nature. Molecules like RNA can also have catalytic functions. RNA that functions as enzymes are known as ribozymes. E.g. An RNA molecule found in ribosome, called peptidyl transferase, catalyses formation of peptide bond between amino acids during protein synthesis. (Details will be covered in Core Idea 2) 2 PROPERTIES OF ENZYMES 2.1 Enzymes are specific Enzymes have a specific active site which recognises and binds to specific groups of atoms or type of bond present in