Animation of biosensor

This represents the lower tip of a specific electrode for glucose. The gray skinny rectangles are the electrode elements. The blue line is a membrane enclosing a solution (yellow) with the enzyme. Green blobs represent microbial cells. Red spheres are glucose. If the applet is working properly, the cells cannot penetrate the membrane and must remain outside. Glucose is very small and penetrates easily to react with the aid of the enzyme to consume oxygen. Reaction is shown as an orange halo. This changes the current that flows between the electrode elements.

To summarize:

  • A cell cannot penetrate the membrane.
  • Small molecules that penetrate but don't react have no effect.
  • Glucose can penetrate and react, but oxygen is needed. This oxygen is generated by the enzymatic reaction within the membrane compartment.
  • Current that flows through the electrode elements depends on breaking down oxygen.

    Applet errors:

  • The glucose molecules that react should disappear.
  • In an aerated system, fresh oxygen enters the culture fluid. It can enter the membrane compartment. Thus the sensor detects oxygen and glucose. However, active cells keep the concentration of oxygen quite low outside so that the sensor is OK because the local oxygen concentration generated inside the membrane compartment reflects glucose concentration quite well.
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  • Done