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The effect of enzyme concentration on the rate of reaction.

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Introduction

THE EFFECT OF ENZYME CONCENTRATION ON THE RATE OF REACTION Maria Mulvany Ashlawn School Candidate number: 8160 THE EFFECT OF ENZYME CONCENTRATION ON THE RATE OF REACTION Aim: To find out how the concentration of enzyme effects changes in the rate of reaction BACKGROUND INFORMATION ON ENZYMES Enzymes are globular proteins, coiled into a precise three-dimensional shape. They are biological catalysts, speeding up chemical reactions without being affected or used up. Enzymes speed up reactions where molecules are split or joined together. The molecule, or molecules in the reaction bind to a special feature on the enzyme called the active site. The enzyme is folded in such a way that the catalytic amino acids are positioned in a region forming the active site. it is usually a depression or groove on the surface of the enzyme The active site has a complimentary shape to that of the substrate, allowing a perfect fit. This is describing the lock and key theory, where the enzyme is the lock and the substrate is the key.(see figure A). This theory has been modified to the induced fit hypothesis. This states that when the enzyme and the substrate bind, it induces the enzyme structure to fit. (see figure B). A Enzyme and Substrate Enzyme-substrate complex Enzyme and released products B Shape changes as enzyme and substrate bind Reaction proceeds as they bind Original shape returns as products are released In the particular example shown in the diagram, the substrate is split into two products. ...read more.

Middle

or the ferric (Fe+++) oxidation state. Other enzymes also have variable effects on reactions dependent on the concentration. For example, carbonic anhydrase and maltase. CARBONIC ANHYDRASE Carbonic anhydrases are enzymes that catalyse the hydration of carbon dioxide and the dehydration of bicarbonate in the human body. CO2 + H2O <-----> HCO3- + H+ Carbonic anhydrase isozymes are metalloenzymes consisting of a single polypeptide chain complexed to an atom of zinc. They are incredibly active catalysts, with a turnover rate (kcat) of about 106 reactions per second.3 These carbonic anhydrase-driven reactions are of great importance in a number of tissues where the concentration of the enzyme will affect the rate of reaction. Examples include: Parietal cells in the stomach secrete massive amounts of acid (i.e. hydrogen ions or protons) into the lumen and a corresponding amount of bicarbonate ion into blood. Pancreatic duct cells do essentially the opposite, with bicarbonate as their main secretory product. Secretion of hydrogen ions by the renal tubules is a critical mechanism for maintaining acid-base and fluid balance. Carbon dioxide generated by metabolism in all cells is removed from the body by red blood cells that convert most of it to bicarbonate for transport, then back to carbon dioxide to be exhaled from the lungs. MALTASE Maltase is a glycosidase. It catalyses the hydrolysis of glycoside bonds. The action of maltase on maltose is usually written as:4 maltase Maltose Glucose Increasing the concentration of maltase will affect the rate of production of glucose. ...read more.

Conclusion

clamp B * Attach test tube to clamp A * Put on goggles [**REPEAT EXPERIMENT FROM HERE] * Measure 20 cm3 of Hydrogen peroxide in a measuring cylinder into the test tube * Place the bung and deliver tube into test tube to minimise the evaporation of the hydrogen peroxide * Feed the delivery tube into the inverted measuring cylinder * Place stopwatch in front of clamp A, ready for use * Lift the bung off the test tube and drop the potato with the smallest surface area into the test tube * Push the bung down and start the stopwatch at the same time * Time for three minutes so that a measurable amount of oxygen is produced * Take out delivery tube from the measuring cylinder * Record the volume of oxygen collected/volume of water displaced in the results table and fill in the surface area of the potato, volume of hydrogen peroxide and time period * Take the off the bung from the test tube and detach the test tube from the clamp and place in the test tube rack * Take a clean test tube and attach to clamp A * Tip away the hydrogen peroxide and dispose of potato cubes * Repeat experiment from **asterisked point above. Follow the same method, using a different set of potato cubes with increased surface area. * Repeat the whole method to get a second set of results and record in the repeat column on the same results table. ...read more.

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