Bio molecules > end-point

This activity involves skills for safe handling of microbial material. Students compare the activity of an enzyme extract with that of two enzyme-producing microbes and can consider the industrial importance of enzymes and microbes.

Phenolphthalein is an indicator that is pink in alkaline solutions of about pH10. When the pH drops below pH 8.3 phenolphthalein goes colourless. Here, an alkaline solution of milk, lipase and phenolphthalein will change from pink to colourless as the fat in milk is broken down to form fatty acids (and glycerol) thus reducing the pH to below 8.3. The time taken for

Measure the time taken for amylase to completely break down starch, by withdrawing samples at 10 second intervals and noting the time at which the solution no longer gives a blue-black colour with iodine solution (but the iodine solution remains orange). Use buffers to provide solutions at different pHs. Calculate the rate of this enzyme controlled reaction by calculating 1

Exposed and developed black and white negative film is black because it contains light-sensitive silver halides (salts). Black and white film is composed of a plastic backing covered with a mixture of gelatine (protein) and silver halides. Digestion of the gelatine (protein) by trypsin releases the silver salts and the film clears. The time taken for the film to clear will be

This is a simple protocol allowing students to construct a calibration curve from which to estimate the concentration of protein in a sample of milk powder. It allows discussion of accuracy, error and reliability. It also allows discussion of the difference between quantitative and qualitative tests, and the commercial applications of analytical techniques like this.