AS Biology Topic 2 (2.2.4)

Which colour indicates the lowest concentration of reducing sugar present in a solution after testing with Benedict's solution?

• brown

• green

• red

• yellow

Which carbohydrate gives a brick red colour when boiled with Benedict's solution?

• cellulose

• fructose

• glycogen

• sucrose

Steps 1-4 are used to test for a non-reducing sugar

1. Put 5cm³ of solution into a test-tube

2. Add a few drops of acid

3. Neutralise with alkali

4. Add 6cm³ Benedict's solution

When is the solution boiled?

• Between steps 1 and 2

• Between steps 2 and 3 and after step 4

• Between steps 2 and 3 only

• After step 4 only

A sample of a solution was tested for reducing sugar and the result was negative. Another sample of the same solution was then tested for non-reducing sugar and the result was positive. Which step in the test for non-reducing sugar breaks the glycosidic bonds?

• addition of Benedict's reagent

• addition of sodium hydroxide

• boiling with hydrochloric acid

• heating to 80 degrees celcius

Solutions of three biological molecules are tested for sugars. The table shows the colours of the solutions after testing.

Which solutions contained glucose before testing?

• 1, 2 and 3

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

After boiling a sample of milk with Benedict's solution, a yellow colour is observed. Which conclusion about the sample of milk is correct?

• Reducing sugars are not present

• Reducing sugars are present

• There is a high concentration of fructose

• There is a low concentration of sucrose

A sample of food was heated with Benedict's solution which changed colour to green. A second sample of the same food was boiled with dilute hydrochloric acid and neutralised using sodium hydrogencarbonate. It was then heated with Benedict's solution which changed colour to red. What did these results show?

• A

• B

• C

• D

The colour of a positive Benedict's test is due to the formation of copper oxide. The mass of copper oxide is proportional to the mass of reducing sugar present. Samples of fruit juice were tested for the presence of reducing sugars and non-reducing sugars using the Benedict's test. The table shows the mass of copper oxide after boiling with Benedict's solution and after acid hydrolysis and boiling with Benedict's solution. Which sample contained the most non-reducing sugar?

• A

• B

• C

• D