Transcript Slideshow
• Look at the key words • How many seem familiar? • Turn it over and now look at the definitions • How many words could you match up from memory? • Now using the definitions and table, jot down the word and definition (why not number them and write them up for consolidation) 1 of 20 31 © Boardworks Ltd 2005 2004 1.7 Enzyme action Recap: • • • • Primary Secondary Tertiary Quaternary • Levels of protein structure, what happens at each, what kind of bonding, additional info, examples etc 5 mins LO: • How do enzymes speed up chemical reactions? • How does the structure of enzyme molecules relate to their function? • What is the lock and key model of enzyme action? Week 18 Primary structure to tertiary structure in enzymes © Pearson Education Ltd 2008 This document may have been altered from the original Enzymes the biological catalysts: • Enzymes are globular proteins. • Enzymes are catalysts. • Catalysts speed up chemical reactions without undergoing permanent changes. • Enzymes/catalysts are not used up in chemical reactions and can therefore be reused repeatedly. Enzymes lower the activation energy: Sucrose + water glucose + fructose • For the reaction to take place a number of things must happen. • 1st the sucrose & water must collide with sufficient energy to form glucose & fructose. • The energy of the products must be less than that of the substrates. • An initial boost of energy is needed to start the reaction- the activation energy. Activation Energy: • An energy barrier that must be overcome before the reaction can proceed. • Enzymes lower the activation energy. • The reactions will occur at a lower temperature. • With out enzymes 37oC would be to cold for reactions to proceed at a fast enough rate to support life. Reactants = substrate Week 18 Activation energy (maltose to glucose) How the enzyme maltase lowers the activation energy needed to convert maltose to glucose (no boiling in acid required!) © Pearson Education Ltd 2008 This document may have been altered from the original Enzyme substrate complex: • The active site forms a small hollow depression within the enzyme molecule. • The molecule on which the enzyme acts is called the substrate. • The substrate is a complementary shape to the active site • The two fit to form the enzyme- substrate complex. • Temporary bonds form between the amino acids of the active site and groups on the substrate molecule. 1 10ofof20 31 Key vocab © Boardworks Ltd 2005 2004 The lock-and-key hypothesis Week 18 – we don’t think this is how it works anymore due to increasing scientific evidence about binding to other areas of the enzyme leading to decreased activity – suggests it would have changed the shape © Pearson Education Ltd 2008 This document may have been altered from the original Induced fit model: 1 12ofof20 31 Like a hand fitting into a glove (enzyme) – it ‘moulds’ around the hand (substrate) © Boardworks Ltd 2005 2004 Tasks: Exam questions Questions to complete • Why is the induced fit a better model than the lock and key theory? • Are all proteins enzymes? • Do all proteins have an active site? • Do all molecules have active sites, or other sites? Enzymes dominoes Key words and definitions activity. Week 18 A metabolic pathway © Pearson Education Ltd 2008 This document may have been altered from the original Week 18 Mould produces extracellular enzymes to digest bread © Pearson Education Ltd 2008 This document may have been altered from the original Week 18 Lysosome and phagocytosis © Pearson Education Ltd 2008 This document may have been altered from the original Week 18 Phenylketonuria sequence and effects © Pearson Education Ltd 2008 This document may have been altered from the original