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Aim: Toinvestigate whether immobilised enzymes are less susceptible to denaturisationthan non-immobilised enzymes by measuring the time taken at differenttemperatures for the enzyme to denature.

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Introduction

Aim: To investigate whether immobilised enzymes are less susceptible to denaturisation than non-immobilised enzymes by measuring the time taken at different temperatures for the enzyme to denature. Background Knowledge: Enzymes are globular proteins, they act as catalysts (substances which speed up chemical reactions without being altered or destroyed in the process). All enzymes contain an active site; this gives the enzymes its catalytic properties. The active site has an affinity for the substrate, and is made of amino acids which usually do not neighbour each other but are brought together by 3D folding of the protein. The different structures of the protein provide different functions for the enzyme. The primary structure is the arrangement of amino acids in the molecule and is therefore responsible for the specificity of the enzyme. The secondary structure develops when the polypeptide chain takes up a particular shape. This determines whether the protein is globular or structural. The tertiary structure is the 3D folding of the structure; this allows the enzymes to be re-used and forms the active site. The quaternary structure is when two or more proteins bond together forming a biologically active molecule. ...read more.

Middle

Enzymes and Denaturisation Denaturisation of an enzyme is due to the loss of its 3D structure. It happens when the relatively weak bonds that maintain the tertiary structure are changed. It may be due to exposure to high temperatures, heavy metal ions, extremes of pH and some organic solvents. Immobilisation of Enzymes Immobilised enzymes are enzymes which are held in granules, or attached to fibres, then packed into a column through which a supply of the reactants is continually passed, to form the product. There are different methods of enzyme immobilisation; Entrapment; the enzyme is mixed with gel-forming ingredients and when the gel forms the enzyme remains "trapped" in the gel matrix. The pores are large enough to let the substrate in, but not the enzyme out. Covalent bonding; the enzyme is covalently bonded to a matrix, which prevents enzyme molecules from being leached away. Some enzyme molecules may be denatured by the bonding process. Adsorption; the enzyme is Adsorbed to various surfaces, but because the attachment is not permanent this method is usually only used for scientific studies or for "disposable" enzymes. Encapsulated in a compartment behind a semi-permeable membrane Direct cross-linking; the enzyme molecule is covalently bonded with bridging molecules, reactants and products have easy access, but some enzymes might be denatured. ...read more.

Conclusion

(9) If there is no colour change, it means the enzyme has been denatured. Non - immobilised Enzymes (1) Predication I think that the immobilised lactase will denature at higher temperatures than the non-immobilised enzyme therefore suggesting that the immobilised lactase is less susceptible to denaturisation. As the enzyme is trapped in the gel-like substance, it allows the substrate to enter and exit however restricts the enzyme from leaving the entrapment substance. Therefore making the enzyme more stable, and providing it with a delicate barrier against its surroundings. I think this delicate barrier will help protect the tertiary structure from losing its shape (to an extent) because some the increase in vibrational energy, caused by the increase in temperature, will be absorbed by the inert matrix rather than the enzyme itself. Therefore, helping to secure the active site of the enzyme from the detrimental effects of excessive heat energy. The non immobilised lactase does not have this inert matrix to protect its active site/ tertiary structure therefore when excessive temperatures are present the vibrational energy will cause the weak bonds which hold the tertiary structure in place to change thus denaturing the enzyme. This signifies, that immobilised enzymes are less susceptible to denaturisation ...read more.

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