Enzymes Enzymes are proteins that act as biological catalysts They lower the activation energy of a specific chemical reaction Lowering the activation energy has a profound effect on how rapidly the reaction is completed

Enzymes Lower the activation energy of a reaction 2

Enzymes Lower Activation Energy

What are enzymes? Enzymes are typically proteins Enzymes are specific Enzymes act as catalysts to speed up the rate of reaction of a biological process Enzymes are not used up by the reaction they catalyse Enzymes were discovered by a German chemist called Eduard Buchner near the end of the nineteenth century. He discovered enzymes while trying to extract yeast fluid for medicinal use when he noticed that the sugar was continually being converted into alcohol. Even though Louis Pasteur had shown this about twenty years before Eduard Buchner, Louis Pasteur had said that it was the yeast itself that made the conversion.Eduard Buchner said that it was not the yeast but the ‘juice’ inside them. The word enzyme was used for the active ingredient in the yeast juice. Enzyme literally means ‘in yeast’ ( ‘en’ = in, ‘zyme’ = yeast) and all enzymes are used as organic catalysts to speed up chemical reactions in organisms.Without enzymes reactions in cells would be so slow that they would virtually not take place.

Enzymes are essential to all forms of life…

Enzymes: Vocabulary Check Catalyst: A substance that speeds up a chemical reaction without itself being changed Enzyme: A biological catalyst that is usually a protein Substrate: The reactant(s) upon which an enzyme has its action Product: A substance that results from a chemical reaction

Enzyme-Substrate Interaction

Factors affecting Enzymes Substrate concentration Enzyme availability pH Temperature Inhibitors

Factors which affect enzyme activity 1: Temperature From: GCSE Bitesize:26.08.12 http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/homeostasis/importancerev4.shtml

The effect of temperature Temperature / °C Enzyme activity 10 20 30 40 50 Q10 Denaturation

The effect of temperature For most enzymes the optimum temperature is about 30°C Many are a lot lower. For example, cold water fish can die at 30°C since many of their enzymes denature A few bacteria have enzymes that can withstand very high temperatures up to 100°C Most enzymes are fully denatured at 70°C

Factors which affect enzyme activity 2: pH From: GCSE Bitesize:26.08.12 http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/enzymes/enzymes1.shtml

The effect of pH Optimum pH values Enzyme activity Trypsin Pepsin pH 1 3 5 7 9 11 © 2007 Paul Billiet ODWS

The effect of pH Extreme pH levels will produce denaturation The structure of the enzyme is changed The active site is distorted and the substrate molecules will no longer fit in it At pH values slightly different from the enzyme’s optimum value, small changes in the charges of the enzyme and its substrate molecules will occur This change in ionisation will affect the binding of the substrate with the active site due to shape change.

Factors which affect enzyme activity 3: Substrate and enzyme concentration From: http://www.skinnersbiology.co.uk/enzyme.htm August 26th 2012

Complete this sentence… The _____________ (more/less) enzyme, the faster the product is made.

Substrate concentration: Enzymic reactions Reaction velocity Substrate concentration Vmax Faster reaction but it reaches a saturation point when all the enzyme molecules are occupied. If you alter the concentration of the enzyme then Vmax will change too.

Enzyme action can be blocked by: 1. Inhibition (many drugs work through enzyme inhibition) 2. Denaturation

Enzyme Inhibition

Denaturation Denaturation is a change in the shape of an enzyme which prevents it from fulfilling its function. Enzymes (and other proteins) can be denatured by heat, pH changes, or certain chemicals NB: Denaturation is not the same as ‘killing’ – proteins and enzymes are not living things, so can’t be killed!

What does ‘enzyme denaturation’ mean?