1.3- Carbohydrates-disaccharides and polysaccharides

Question 1

Define disaccharide

Answer 1

Two monosaccharides joined together

Question 2

What is maltose formed from?

Answer 2

Glucose+glucose

Question 3

What is sucrose formed from?

Answer 3

Glucose+sucrose

Question 4

What is lactose formed from?

Answer 4

Glucose+galactose

Question 6

What is the reaction that joins monosaccharides and what bond forms?

Answer 6

Condensation reactions
Glycosidic bond

Question 7

What is the reaction that breaks glycosidic bonds?

Answer 7

Hydrolysis
Involves a water molecule

Question 8

Describe the test for non-reducing sugars

Answer 8

1. Carry out the test for a reducing sugar
2. If the solution doesn’t change colour a reducing sugar isn’t present
3. Add 2cm3 of the food sample and an equal volume of HCL to a test tube
4. Heat in a water bath for 5 mins
5. Slowly add some sodium hydrogen carbonate solution to the test tube
6. Heat with Benedict’s solution in a water bath for 5 mins
7. If a reducing sugar is present the solution will turn orange

Question 9

What is the purpose of adding HCL?

Answer 9

To hydrolyse any dissachraide present into its constituent monosaccharides

Question 10

What is the purpose of adding sodium hydrogen carbonate?

Answer 10

To neutralise the HCL
Benedict’s reagent doesn’t work under acidic conditions

Question 12

Define polysaccharide

Answer 12

Polymers formed by combing many monosaccharides

Question 13

Why are polysaccharides insoluble and explain the benefit of this feature

Answer 13

They are large molecules
Good for storage

Question 14

Describe the test for starch

Answer 14

1. Place 2cm3 of the sample being tested into a test tube
2. Add two drops of iodine solution
3. If starch is present the solution turns black/blue