YEAR 12 - AS Biology 29th November 2005 Enzymes Mr Potter Lesson Objectives • Enzyme unit overview – What are they? – How they work • Activation.
Download ReportTranscript YEAR 12 - AS Biology 29th November 2005 Enzymes Mr Potter Lesson Objectives • Enzyme unit overview – What are they? – How they work • Activation.
YEAR 12 - AS Biology 29th November 2005 Enzymes Mr Potter Lesson Objectives • Enzyme unit overview – What are they? – How they work • Activation energy – What controls their activity • Rates of reaction • Substrate/enzyme concentrations • Temperature, pH • Enzyme inhibitors – Practical to demonstrate “Catalase” activity in different tissue samples Previous related topics covered? • • • • Enzyme controlled reactions? Proteins? Lipase, protease, pectinase, amylase etc? “Lock & Key” molecular structures? By the end of the unit you should be able to:• Explain enzymes as Globular Proteins which act as catalysts • Explain their catalytic action in terms of lowering activation energy • Describe examples of enzyme-catalysed reactions • Discuss factors affecting reaction rates and inhibition • Describe how to investigate these effects experimentally • Enzymes:– Are defined as a BIOLOGICAL catalyst i.e. something that speeds up a reaction. Up to 1012 fold – Usually end in ‘…ase’. – Discovered in 1900 in yeasts. Some 40,000 in human cells – Control almost every metabolic reaction in living organisms – Are globular proteins coiled into a very precise 3-dimentional shape with hydrophilic side chains making them soluble – Possess an active site such as a cleft in the molecule onto which other substrate molecules can bind to form an enzyme-substrate complex – Once the substrate has been either synthesised or split, enzymes can be re- used. – Do not ‘create’ reactions – Widely used in industrial cleaning – Often require co-factors (co-enzymes) to function – metal ions, or vitamin derivatives Amylase + starch substrate How do enzymes work? • Reaction Mechanism – In any chemical reaction a substrate is converted into a product. – In an enzyme catalysed reaction the substrate first binds to the active site of the enzyme to form the enzyme-substrate complex Molecule Geometry • Substrate molecule fits into the enzyme like a lock & key. • Enzyme shape distorts or it changes other factors to make the reaction happen “Activation Energy” • In a ‘natural’ reaction the product has a lower energy than the substrate so equilibrium will take it in the direction of the product. • However there is an energy ‘barrier’ to be overcome • Enzymes lower the activation energy required to bring about a reaction. • EG catalase reduces the activation energy for the reduction of H202 86-fold Reaction rate factors • Substrate concentration – Initially rate increases with substrate conc. This powerpoint was kindly donated to www.worldofteaching.com http://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.