1.3 - Carbohydrates - Disaccharides And Polypeptides

Question 1

Glucose joined to glucose forms what?

Answer 1

Maltose

Question 2

Glucose joined to fructose forms what?

Answer 2

Sucrose

Question 3

Glucose joined to galactose forms what?

Answer 3

Lactose

Question 4

When the monosaccharides join what type of reaction is it?

Answer 4

A condensation reaction

Question 5

What bond is formed between monosaccharides?

Answer 5

Glycosidic bond

Question 6

What type of reaction is it when a disaccharide is broken down into its monosaccharides?

Answer 6

Hydrolysis

Question 7

What is added that causes the breakdown in hydrolysis?

Answer 7

Water

Question 8

Some disaccharides are what?

Answer 8

Reducing sugars

Question 9

In order to detect a non - reducing sugar it must be what?

Answer 9

Hydrolysised into its monosaccharide components by hydrolysis

Question 10

What is the process of detecting a reducing sugar?

Answer 10

1. If the sample is not already in liquid form, it must first be ground up in water
2. Do the Benedict’s test on it if it fails to change colour then:
3. Add another 2cm^2 of the food sample to 2cm^2 of dilute hydrochloric acid in a test tube and place the test tube in a gently boiling water bath for 5 minutes
4. Slowly add some hydrogen-carbonate solution to the test tube
5. Re do the Benedict’s test on it if it goes from blue black to orange brown then a reducing sugar is present

Question 11

Why do you add dilute hydrocloric acid to the food sample?

Answer 11

It will hydrolyse any disaccharide present into its monosaccharides

Question 12

Why do you add sodium hydrogen-carbonate solution to the food sample

Answer 12

To neutralise the hydrochloric acid (Benedict’s reagent wont work in acidic conditions)

Question 13

What are polysaccharides?

Answer 13

Polymers, formed by combining together many monosaccharides

Question 14

Polysaccharide are very large molecules meaning they are?

Answer 14

Insoluble

Question 15

What is good about polysaccharides being insoluble?

Answer 15

Makes then suitable for storage

Question 16

Some polysaccharides, such as cellulose are not used for storage but for what?

Answer 16

Giving structural support for plants

Question 17

What is the test for starch?

Answer 17

Iodine test

Question 18

What is the method for the iodine test?

Answer 18

1. Place 2cm^2 of the sample being tested into a test tube
2. Add two drops of iodine solution and shake or stir
3. If there is starch present the solution will turn from orange to blue black