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An Investigation into the Effect of Temperature on an Enzyme Catalysed Reaction.

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An Investigation into the Effect of Temperature on an Enzyme Catalysed Reaction. The aim of our investigation is to show how various temperatures affects the rate at which oxygen and water are produced in the catalysed reaction of Hydrogen Peroxide. The catalyst we are going to use is found naturally occurring in potato. Background Information: Enzymes can be divided into two main groups, intracellular and extracellular. Intracellular are found inside the cell, from where the control metabolism. These cells will also produce the extracellular cells, but these achieve their affect outside the cell. These include digestive enzymes that break down food in the gut. An enzyme is named by adding the suffix - ASE to the substrate, which it acts upon. Hydrolase's catalyse the hydrolysis of a substrate by the addition of a water molecule. Oxoreductases are involved with redox reactions. Transferases transfer a group of atoms from one molecule to another, and so on. Enzymes are complex globular proteins, folded up into a precise 3d shape. They are made from a long polypeptide chain, which in a globular protein is wound and folded into a precise spherical shape. Hydrogen, ionic, disulphide bonds as well as hydrophobic interactions all hold the chain in its three dimensional shape. The precise shape of the active site, the place at which the substrate is to bind, is so because the enzyme is specific to one substrate, hence the need for specificality. ...read more.


Acidity and alkalinity can affect the active site of an enzyme. Free hydrogen or hydroxyl ions can affect the charges on the amino acid side chains of the enzymes active site. This will also affect the hydrogen bonds. If the bonds break due to a change in charge the three-dimensional shape will be lost, thus changing the shape of the active site. The substrate will no longer fit into the active site and will not be able to for an enzyme-substrate complex. Meaning that the enzyme looses its activity and the rate of reaction falls. Low pH Correct pH High pH Temperature: Heating increases the rate of reaction in most chemical reactions. Heating a substance gives it greater kinetic energy, thus making the substance move around more. This means that there is a greater chance of molecules colliding, increasing the rate of reaction. Increasing the temperature of an enzyme-controlled reaction will increase the rate o9f reaction but only up to a point. For most enzymes in the human body the rate will increase up to 40oc, a little higher than body temperature, known as the optimum temperature. This rise will bring about a corresponding rise in the rate of reaction. The optimum temperature is specific to the enzyme and has a lot to do where the enzyme is found. ...read more.


To ensure that this was measured precisely, 5ml syringes were used to accurately gauge to exact quantities. iv) Inhibition - Inhibitors compete with the substrate for the active sites of the enzyme (competitive inhibitors) or attach themselves to the enzyme, altering the shape of the active site so that the substrate is unable to occupy it and the enzyme cannot function (non-competitive inhibitors). Inhibitors therefore slow the rate of reaction. They should not have affected this investigation, however, as none were added. v) Enzyme cofactors - cofactors are none protein substances which influence the functioning of enzymes. They include activators that are essential for the activation of some enzymes. Coenzymes also influence the functioning of enzymes although are not bonded to the enzyme. Unless enzyme cofactors were present in the potato tissue containing the Catalase, they were not included in this investigation and therefore would not have affected the rate of reaction and the results of this experiment. vi) Enzyme Concentration - Provided there is an excess substrate, an increase in enzyme concentration will lead to a corresponding increase in rate of reaction. Where the substrate is in short supply (i.e. it is limiting) an increase in enzyme concentration has no effect. I varied the enzyme concentration by altering the number of equal sized discs of potato that contain the Catalase, in the reaction. The greater the number of discs, the greater the enzyme concentration. Apparatus - Rebecca Worley Biology ...read more.

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