2.2 Qualitative And Quantitative Tests for biological molecules

Question 1

Whats the test for reducing sugars?

Answer 1

• Place a sample of food to be tested in a boiling tube
• Add Benedict’s solution then heat in a water bath at 80 degrees celsius for 3 minutes

Question 2

What would the result be of heating a reducing sugar with Benedict’s solution be ?

Answer 2

A colour change to an orange-red precipitate indicates a reducing sugar is present
•When low levels of reducing sugars are present, the contents of the boiling tube may appear yellow or green

Question 3

What is the test for non-reducing sugars ?

Answer 3

With non reducing sugars, we have to hydrolyse the bond first
•First test a sample for reducing sugars to check there are none there in the first place
•Take a separate sample and boil it with hydrochloric acid to hydrolyse the glucose and fructose
•Cool the solution and use sodium hydrogencarbonate solution to neutralise it
•Test for reducing sugars again

Question 4

What would the result be of heating a non reducing sugar with Benedict’s solution be ?

Answer 4

A positive result (green-yellow-orange-red) indicates that non-reducing sugar (e.g. sucrose) was present in the original sample

Question 5

What is the test for lipids?

Answer 5

The emulsion test
•Take a sample and mix it thoroughly with ethanol. (Water is not used as lipids are insoluble in it)
• Filter
• Pour the solution into water in a clean test tube

Question 6

What are the results for a lipids test?

Answer 6

A cloudy white emulsion indicates the presence of lipids. This is made up of tiny lipid droplets that come out of solution when mixed with water

Question 7

What is the test for proteins?

Answer 7

Biuret test
• Place a sample of food to be tested in a well on a spotting tile

Question 8

What would the result be for testing proteins?

Answer 8

Lilac colour indicates protein is present

Question 9

What can you use to quantify the concentration of sugar in the original sample

Answer 9

by assessing how these two variables change, using a technique called colorimetry

Question 10

How does a colorimeter work?

Answer 10

By shining light through a sample—> using a centrifuge to separate the precipitateand any excess

Question 11

What is mitosis

Answer 11

Mitosis is one part of a much longer process called the cell cycle