Enzyme investigation

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Introduction: An Enzyme is any one of many specialised organic substances, composed of polymers of amino acids, that act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms. Those enzymes identified now number more than 700.

Enzymes are classified into several broad categories, such as hydrolytic, oxidising, and reducing, depending on the type of reaction they control. Hydrolytic enzymes accelerate reactions in which a substance is broken down into simpler compounds through reaction with water molecules. Oxidising enzymes, known as oxidises, accelerate oxidation reactions; reducing enzymes speed up reduction reactions, in which oxygen is removed. Many other enzymes catalyse other types of reactions.

Individual enzymes are named by adding ASE to the name of the substrate with which they react. The enzyme that controls urea decomposition is called urease; those that control protein hydrolyses are known as proteinases. Some enzymes, such as the proteinases trypsin and pepsin, retain the names used before this nomenclature was adopted.

( Fig 1.0 on the following page )

Structure and Function of an Enzyme

Enzymes are large proteins that speed up chemical reactions. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate fail to bind if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate.

Preliminary work: For this, I wanted to see how many potato discs would be a good number to do the actual experiment. I used the same experiment I am going to use to find the effect of temperature on enzymes but instead of varying the temperature, as I am going to do, I varied the amount of potato discs in the test tube. Overall, I took 6 readings of a different number of discs. At first, I used 2; then I went onto 4, and so on up to 12. (2, 4, 6, 8, 10, 12) I found out that the ideal number of discs was 8 so I am going to use 8 in my experiment of varying temperature.

Results of research work:

No. of Potatoes

(amount) Time to reach 5cm3

(seconds)

4 41.4

6 33.2

8 30.4

0 20.1

2 18.4

Apparatus: I have decided to use the following equipment in order to carry out my experiment:

-Water Baths

-Ice Baths

-Test Tube/Boiling tube

-10 cm3 Measuring cylinder

-2 cm3 of Hydrogen Peroxide

-1 cm of circular potato chips

-Manometer

-Borer

-Stopwatch

Methods: At first, I will have to get the potato so I will use a Borer to cut a cylinder of potato out of the whole one and from there I will cut up the potato cylinder into segments of 1 cm using a razor. I will then put them into a test tube containing 10 cm3 of pH.7 buffer solution and place it in their designated water/ice baths along with the 10 cm3 of Hydrogen Peroxide. The water baths range from 0°C to 60°C, with intervals of 10°C. Time will not affect my experiment, as I will leave all the potato chips in the water baths for an equal length of time, my only variable being the temperature, with a range increasing by 10°C each time. I will use this range because I think it will improve the accuracy of my results. Once the Hydrogen Peroxide and buffer solution are at the temperature I want them to be, I will place the Manometer over the test tube as soon as I have put the buffer solution in with the potato discs. I will then start the stopwatch as soon as I have tightened the tap on the manometer, measuring the time it takes for the red dye to move 5cm. This distance is taken from the level point of the dye and will be measured using a ruler and the 5cm mark is drawn with a black chinagraph pencil. I have chosen 5cm because the Manometer tube is not much longer than 5cm. I will repeat this three times to find a mean for this temperature. The procedure will be repeated for the following temperatures: 0°C, 20°C, 30°C, 40°C, 50°C and 60°C. I have evolved on this plan as a result of preliminary work on the topic in which a number of procedures and variables were demonstrated.
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Variables:

? Heat

? pH

? Time for the red dye to reach the 5 cm mark

? Concentration of enzyme of substrate

? Potato

? The surface area of the potato

I am going to vary "a" (the temperature), from above, and control all of the other variables.

I shall only be altering the temperature, as that is my main variable, and so I will therefore keep the others the same in order to make it a fair test, and a comprehensive study ...

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