Chapter1 Testing For Biological Molecules

Question 1

What are the 3 major biological molecules

Answer 1

Carbohydrates proteins and lipids

Question 2

How do you test for sugar

Answer 2

1/ add Benedicts Reagan’s to a sample and heat it in a water that is 75’c. If the text is positive the sample will turn into a coloured precipitate
2/ the higher the concentration of reducing sugar , the further the colour change goes .

Blue ,green ,yellow , orange,brick red

Question 3

How is starch tested for

Answer 3

Iodine

Question 4

How can you tell if starch is present ( what is the test )

Answer 4

If starch is present the soloution changes colour form browny orange to blue/black colour

Question 5

How do u test for lipids

Answer 5

Use the emulsion test

1/ shake the substance with ethanol for about a minute until it dissolves , then pour the solution into water.

2/ if there are lipids , they will precipitate out of the milky liquid and show up as a milky emulsion

3/ the more lipids there are the more milky the colour

Question 6

What is the test for proteins

Answer 6

The bieuret test

1/ add a few drops of potassium hydroxide solution to make the solution alkaline
2/. Then add some copper sulphate solution
3/if there is no protein the solution will stay blue
If there is protein the solution will turn purple