Investigating how concentration of enzyme affects the rate of an enzyme controlled reaction.

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Sarah Walker

Investigating how concentration of enzyme affects the rate of an enzyme controlled reaction

Background information

Every enzyme is a protein; proteins are one of the most complicated of the organic molecules. Below is a simplified description of proteins, enzymes and the way they work.

Proteins are made up of monomers (building blocks) called amino acids, these amino acids link together in different orders with special bonds called ‘peptide bonds’, when they are linked together they form a straight chain known as a polypeptide chain. This chain can be coiled or folded into shapes; either alpha helixes or beta pleated sheets, bonds link these together in different ways creating a unique structure, which in the case of enzymes is globular (roughly spherical).

Enzymes are catalysts to organic reactions (they increase the speed of the reaction without changing it or themselves). Every enzyme catalyses a different reaction, this is because the enzyme has an area called the active site which also has a unique shape into which only one type of substrate (substance being reacted) fits. The enzyme breaks the substrate down into products, the diagram below demonstrates this:

An enzyme can have its unique shape broken down by very high temperatures or extreme pH as these break the bonds which hold them together, this disfigures the active site of that particular enzyme and the substrate no longer fits; the reaction stops.

The concentration of the enzyme is directly proportional to the speed of the reaction until the substrate has all been reacted. The concentration of the substrate also affects the rate of reaction but in a slightly different way; there is a rapid rise in reaction rate as the concentration begins to increase, but this eventually gets slower and stops when the enzyme is working at its maximum velocity.

 

Enzyme controlled reactions are sensitive, below are listed the factors which can be varied to change the effectiveness of an enzyme.

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  • Concentration of substrate.
  • Concentration of enzyme.
  • Volume of substrate.
  • Volume of enzyme.
  • Temperature of substrate previous to being added to enzyme.
  • pH of enzyme.
  • pH of substrate.
  • Temperature of enzyme.
  • Temperature of substrate.

An experiment to investigate how enzyme concentration affects an enzyme controlled reaction using catalase and hydrogen peroxide (following original method)

  Apparatus

  • A 1000cm3 beaker
  • A 25 cm3 measuring cylinder
  • A test tube
  • A bung
  • A 10cm3 syringe
  • A delivery ...

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