3. 1. 2 Carbohydrates

Question 1

What are monosaccharides?

Answer 1

Monosaccharides are the monomers from which larger carbohydrates are made.

Question 2

Give 3 examples of monosaccharides.

Answer 2

Glucose, galactose and fructose are common monosaccharides.

Question 3

What does a condensation reaction between two monosaccharides form?

Answer 3

A condensation reaction between two monosaccharides forms a glycosidic bond.

Question 4

How are disaccharides formed?

Answer 4

Disaccharides are formed by the condensation of two monosaccharides.

Question 5

Give 3 examples of disaccharides.

Answer 5

Maltose, sucrose and lactose.

Question 6

How is maltose formed?

Answer 6

Maltose is a disaccharide formed by condensation of two glucose molecules

Question 7

How is sucrose formed?

Answer 7

Sucrose is a disaccharide formed by condensation of a glucose molecule and a fructose molecule.

Question 8

How is lactose formed?

Answer 8

Lactose is a disaccharide formed by condensation of a glucose molecule and a galactose molecule.

Question 9

What is an isomer?

Answer 9

Molecules with the same chemical formula but have different structures.

Question 10

What are the two isomers of Glucose?

Answer 10

a(alpha)-glucose and b(beta)-glucose.

Question 11

How are polysaccharides formed?

Answer 11

Polysaccharides are formed by the condensation of many glucose monosaccharides resulting in the formation of glycosidic bonds.

Question 12

What is formed by the condensation of a(alpha)-glucose?

Answer 12

Glycogen and starch.

Question 13

What is formed by the condensation of b(beta)-glucose?

Answer 13

Cellulose

Question 14

What is the function of glycogen?

Answer 14

A reserve source of energy for the body.

Question 15

What is the function of starch?

Answer 15

Key energy store in plants.

Question 16

What is the function of cellulose?

Answer 16

Provide strength and rigidity to the plant cell wall.

Question 17

What are carbohydrates made up of?

Answer 17

Made up of carbon, hydrogen and oxygen.

Question 18

Describe the test for reducing sugars.

Answer 18

1) Add 2cm^3 of food sample (in liquid form) to a test tube.
2) Then add 2cm^3 of Benedict’s Reagent.
3) Heat mixture in gentle boiling water bath for 5mins

Question 19

Describe the results of the reducing sugars test.

Answer 19

None-blue
Very low-green
Low-yellow
Medium-brown
High-red

Question 20

Describe the test for non-reducing sugars.

Answer 20

1) Carry out Benedict’s test: negative result so no reducing sugars.
2) Hydrolyse the unknown to split the sugar into monosaccharides:
- Add HCl
- Heat in water bath
- Neutralise using hydrogen carbonate
3) Repeat Benedict’s test

Question 21

Describe the results for the non-reducing sugars test.

Answer 21

If it goes brick red this time, there is non-reducing sugars present

Question 22

Describe the iodine test for starch.

Answer 22

1) Dissolve iodine in potassium iodide
2) Add iodine solution directly to food sample

Question 23

Describe the results for the iodine test for starch.

Answer 23

A dark blue-black colour indicates presence of starch.

Question 24

What does quantitative mean?

Answer 24

Relating to, measuring, or measured by the quantity of something rather than its quality.

Question 25

What does qualitative mean?

Answer 25

Relating to, measuring, or measured by the quality of something rather than its quantity.