S1-carbohydrates, disaccharides and polysaccharids

Question 1

What are monosaccharides?

Answer 1

• Soluble substances.
• Sweet-tasting.
• Many join to form polysaccharides.

Question 2

3 examples of monosaccharides.

Answer 2

Glucose, galactose, fructose.

Question 3

What are disaccharides and how are they formed?

Answer 3

• 2 monosaccharides.
• Formed in condensation reaction.
• Glysocidic bonds.

Question 4

3 examples of disaccharides and their monosaccharides.

Answer 4

• Maltose - 2 glucose
• Sucrose - glucose and sucrose
• Lactose - glucose and glactose

Question 5

Monosaccharides and some disaccharides are reducing sugars what is the test for reducing sugars?

Answer 5

BENEDICTS TEST

1. Add a liquid form of a sample to a test tube.
2. Fill with an equal amount of Benedicts reagent.
3. Heat in a water bath.

Positive test=orange-brown.

Question 6

What is reduction? And what are reducing sugars?

Answer 6

Reduction in the gain of electrons or hydrogen.

Reducing sugars are sugars which can donate (reduce) another chemical.

Question 7

How are polysaccharides formed?

Answer 7

• From many monosaccharides.
• In condensation reactions.
• Glycosidic bonds

Question 8

What are polysaccharides?

Answer 8

• Very large molecules.
• Insoluble in water.
• This makes them good for storage.

Question 9

Some disaccharides are non-reducing sugars, what is the test for non-reducing sugars?

Answer 9

1. Add a liquid form of a sample to a test tube.
2. Add with equal amount of dilute hydrochloric acid.
3. Place in a water bath for 5 minutes - the hydrochloric acid will hydrolyse any disaccharides into monosaccharides.
4. Add hydorgencarbonate solution to the test tube to neutralise the hydrochloric acid (test with pH paper
5. Re-test with Benedicts reagent, boiling it in a water bath.

Positive test=orange-brown