The aim of the investigation is to find out what effect temperature has on the activity of pectinase when used in apple juice production.

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Mursil Tafsirullah 12/DR2

Biology: Assessed Practical

Practical Investigation: Effect of temperature on effectiveness on the Activity Pectinase

Aim

The aim of the investigation is to find out what effect temperature has on the activity of pectinase when used in apple juice production.

 Hypothesis And Scientific Reasons

I predict the higher the temperature the greater the volume of juice production until a certain temperature where the enzyme denatures. There will also be a temperature where the enzyme works best; this is known as the optimum temperature. This is due to various reasons, ranging from the enzyme’s structure (shape), its properties and its size. One of these is that the higher the temperature the more kinetic energy the pectinase has which means more movement and a higher chance of collisions between pectin and pectinase. Enzymes catalyse substrates through the fact that the substrates collide with the enzyme causing the substrate to combine with the enzyme forming the enzyme-substrate complex. Enzymes are globular proteins. They have complex tertiary and often quaternary structure in which polypeptides are folded around each other to form a roughly spherical or globular shape. The overall 3-Dimensional shape of an enzyme molecule is very important: if it is altered, the enzyme cannot bind to its substrate and so cannot function. Hydrogen bonds, ionic forces and disulphide bridges maintain the shape of an enzyme. At certain temperatures the hydrogen bond breaks in the polypeptide chain this is know as denaturing. This affects the active site and can render the enzyme ineffective. 

Pectin, which is found inside the apple, can form gels that will bind up liquids. They do this by binding water. However they can only do this when the pectin molecules are very large, for example in fruits such as apples. In fruits pectin naturally functions as a type of ‘glue’ to help hold the cell wall together. The middle lamella in plant cells, which is between two cells, is densely packed with pectin, indicating that pectin helps hold cells together. Pectinase breaks. Pectinase breaks down the pectin split the bonds between the carbon 1 and the carbon 4 atoms of galacturonic acid, thus shortening the chain into smaller molecules. This type of reaction is known as a catabolic reaction, where large molecules are broken down into smaller ones.

In industry they are used in the processing of grapes, apples and oranges (a citrus fruit).

Reaction

During a reaction, the substrate fits into a region on the enzyme surface called the active site.

When denatured

This graph shows what the predicted outcome of the enzyme against temperature reaction to be.

                                                              Enzyme’s Optimum

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                                                     The black dashed line divides the graph into its

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