1.3: Carbohydrates - disaccharides

Question 1

How to make maltose

Answer 1

Glucose + Glucose

Question 2

How to make lactose

Answer 2

Glucose + Galactose

Question 3

How to make sucrose

Answer 3

Glucose + Fructose

Question 4

What is the reaction that joins monosaccharides

Answer 4

A condensation reaction - a molecule of water is removed

Question 5

What bond is formed between monosaccharides

Answer 5

1-4 Glycosidic bond

Question 6

What is the reaction called when a disaccharide is broken down into its monosaccharides

Answer 6

Hydrolysis - water is added which breaks the glycosidic bond

Question 7

What is the test for non-reducing sugars

Answer 7

1. Add 2cm if the food sample being tested and 2cm of Benedicts reagent to a test tube
2. Place the test tube in a gently boiling water bath for 5 minutes. If no colour change then it isn’t a reducing sugar
3. Add another 2cm if the food sample to 2cm of dilute HCL in a test tube and gently heat for 5 minutes
4. Add hydrogen carbonate to alkalise the solution, test with pH paper to see if alkaline
5. Re-test with benedicts reagent, if it turns orange/brown then it is a non-reducing sugar because the dissacharides have been hydrolysed

Question 8

What is a polysaccharide

Answer 8

Many monosaccharides joined together by glycosidic bonds

Question 9

What is an example of a polysaccharide and what is it made of

Answer 9

Starch. Made of alpha glucose

Question 10

What is the test for starch

Answer 10

1. Add 2cm of the sample to a test tube
2. Add two drops of iodine and stir
3. Blue/black colour change = starch