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AS Biology Coursework

Investigating the rate of enzyme activity with varying enzyme concentration

Aim: 

To Investigating the Rate of Enzyme Activity with Varying Enzyme Concentration

Introduction:

Throughout this experiment I will be investigating the effect of enzyme activity whilst varying the enzyme concentration. I will be testing the activity of the enzyme trypsin on the substrate Casein whilst varying the concentration of trypsin.

Trypsin is an enzyme that acts to degrade protein; it is referred to as a proteolytic enzyme or proteinase.  Trypsin enzyme secreted by the pancreas in most animals, which functions in the digestion of proteins.

Pancreatic fluid is introduced into the small intestine through several ducts. It contains trypsin and chymotrypsin, enzymes that split complex proteins into simpler components that can be absorbed and used in reconstructing body proteins.

Trypsin is one of the three principle proteinases to break down dietary protein molecules e.g. Casein, to their component peptides and amino acids.        

        Trypsin continues the process of digestion (begun in the stomach) in the small intestine where a slightly alkaline environment (about p H 8) promotes its maximal enzymatic activity.

Trypsin is the most selective of all the proteolytic enzymes in terms of the restricted number of chemical bonds it will attack. Good use of this fact has been made by chemists interested in the determination of the amino acid sequence of proteins; it is widely employed as a reagent for such molecules.

Casein is the substrate in this reaction with trypsin. It is the predominant phosphoprotein found in fresh milk. It is a globular protein; Casein consists of a fairly high number of  peptides, which do not interact. There are also no disulphide bridges. As a result, it has relatively little  or . Because of this, it cannot . It is relatively , making it poorly soluble in water. It is found in milk as a  of particles called casein micelles which show some resemblance with surfactant-type  in a sense that the  parts reside at the surface. The caseins in the micelles are held together by   and hydrophobic interactions.

Variables:

Independent

My independent variable is concentration/% of the enzyme trypsin. I will manipulate this variable by diluting the trypsin enzyme to gain different concentrations; this will be done by adding the relevant ratio of trypsin to distilled water at room temperature. I am using distilled water because it is has virtually no impurities; this of course could effect the results if it did.

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Table1.

This table shows how I will vary my independent variable-concentration of trypsin. I will keep the concentration of trypsin in a test tube controlled by measuring the volume of each trypsin and distilled water with different measuring syringe (to avoid contamination) and then adding both to the test tube simultaneously. This will bring about more accurate result and less % error.

Apparatus:

  • Test tubes x6

  • Syringe x2

  • Trypsin enzyme 15cm3

  • Casein substrate 5cm3

  • Distilled water (room temperature) 15cm3

  • Goggles

  • Test tube rack

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