Enzymes

• Enzymes increase the rate of reaction by lowering the activation energy of the reaction they catalyse.
• Induced Fit Model

  When the enzyme and substrate bind they form an enzyme substrate complex, and the structure of the enzyme is altered so that the active site of the enzyme fits around the substrate.
• Factors affecting the rate of enzyme-controlled reactions:

  Temperature: rate of reaction increases up to the optimum temperature as the kinetic energy of the enzymes increases. Above the optimum temperature rate of reaction decreases beyond the optimum temperature as the enzyme becomes denatured.
• Factors affecting the rate of enzyme-controlled reactions:

  pH: The pH of a solution is a measure of the hydrogen ion concentration. pH affects the enzymes shape as it can disrupt the bonds in the tertiary structure of the enzyme. Like temperature all enzymes work at different optimum.
• Factors affecting the rate of enzyme-controlled reactions:

  Enzyme concentration: the rate of reaction increases as the enzyme concentration increases as there are more active sites than substrates so substrate concentration becomes the limiting factor.
• Factors affecting the rate of enzyme-controlled reactions:

  Substrate concentration: as concentration of substrate increases, rate of reaction increases as more enzyme-substrate complexes are formed. However, beyond a certain point the rate of reaction no longer increases as enzyme concentration becomes the limiting factor.
• Factors affecting the rate of enzyme-controlled reactions:

  Competitive inhibitors: as concentration of competitive inhibitors increases, rate of reaction decreases as the active sites are temporarily blocked by inhibitors so substrates cannot bind.
• Factors affecting the rate of enzyme-controlled reactions:

  Non-competitive inhibitors: as concentration of non-competitive inhibitors increases, rate of reaction decreases as the shape of the enzyme is altered by the inhibitors.