Wjec/eduqas biochemistry and cells may 2017

marfji

Hi sorry your Q remains unanswered (I only saw it today) (hope your exam is not already done and dusted!)

A biosensor (as the name implies), to look at it simply first, is some mechanism of sensing and measuring biological action or activity. It needs to convert a biochemical source of energy or a biological process/reaction (which can be chemical, nervous, immune-based, etc.) into usually an electrical signal which you can read off an ammeter or voltmeter type of physics gadget (it can also be converted into light energy to measure optical activity).

Any instrument that converts energy from one type to another is called a transducer e.g. in a loudspeaker, electrical signals are converted into physical movement (vibration of a diaphragm) producing sound OR a scanner converts light energy from the document into digital data.

So you need a transducer to convert (in this case i.e. in a biosensor) biological energy into an electrical or optical signal.

Then you measure this electrical or optical energy. For that you use a voltmeter or an ammeter, but it can be more advanced and can be used as an LED viewer, a cathode ray tube or a computer screen, so that the signal can be manipulated in order to get the type of information needed.

e.g. a radioimmunoassay can measure immune system action by attaching a radioactive substance to the antibody and then viewing it on a specialized X-ray.

e.g. an ECG can be looked upon as a biosensor because it adds up the total electrical activity of the heart in various directions and displays it as a printout - there are 12 main "leads" on the electrocardiogram that "look at" the heart from different directions. The ECG is abnormal in heart disease, and the changes seen can aid diagnosis of heart attack, pulmonary embolism (moving clot in the lungs) or a cardiac arrhythmia (irregular heart rhythm), etc.

BEST OF LUCK IN YOUR EXAM!

M (specialist biology tutor)