2.1.14 Biology- Practical biochemistry 2

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Finding out how much is present:

The simple tests described before detect only the presence of the various molecules. If you want to determine how much is present, you need to carry out a quantitative test (a test that gives you a value for the amount present).


Benedict’s test and precipitation:

·         Benedict’s test reveals the presence of reducing sugars.

·         It results in an orange-red precipitate.

·         The more reducing sugar there is present, the more precipitate will be formed, and the more Benedict’s solution (copper sulfate) will be ‘used up’. If the precipitate is filtered out, then the concentration of the remaining solution can be measured.

·         This will tell you how much Benedict’s solution has been used up, so you can then estimate the concentration of the reducing sugar in the original sample.


Comparing solutions with a colorimeter:

·         A colorimeter is a device that shines a light through a sample.

·         A photoelectric cell picks up the light that has passed through the sample. It will give you a reading showing how much light has passed through.

·         Place the solution in a sample chamber


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