Carbohydrates

Question 1

What is a polymer?

Answer 1

A large, complex molecule composed of long chains of monomers joined together

Question 2

What is a monomer

Answer 2

A small, basic molecular unit

Question 3

Give three examples of monomers

Answer 3

1. Monosaccharides
2. Amino acids
3. Nucleotides

Question 4

All carbohydrates contain what elements?

Answer 4

1. Carbon
2. Hydrogen
3. Oxygen

Question 5

Give three examples of monosaccharides

Answer 5

1. Glucose
2. Fructose
3. Galactose

Question 6

What is glucose?

Answer 6

Glucose is a hexose sugar - a monosaccharide with six carbon atoms in each molecule

Question 7

What are the two types of glucose?

Answer 7

1. Alpha glucose
2. Beta glucose

Question 8

What is a condensation reaction?

Answer 8

A condensation reaction is when two molecules join together with the formation of a new chemical bond, and a water molecules released when the bond is formed

Question 9

How do monosaccharides join together?

Answer 9

Condensation reactions

Question 10

What bond joins two monosaccharides together?

Answer 10

Glycosidic bonds

Question 11

What is formed when two monosaccharides join together?

Answer 11

A disaccharide

Question 12

Give three examples of disaccharides

Answer 12

1. Glucose + Glucose = Maltose
2. Glucose + Fructose = Sucrose
3. Glucose + Galactose = Lactose

Question 13

How are polymers broken down?

Answer 13

Hydrolysis reactions

Question 14

What is a hydrolysis reaction?

Answer 14

A hydrolysis reaction breaks the chemical bond between monomers using a water molecule

Question 15

How do you test for a sugar?

Answer 15

Benedict’s test

Question 16

Explain the Benedict’s test for a reducing sugar

Answer 16

1. Add Benedict’s reagent to a sample and heat it in a water bath that’s been brought to the boil
2. If the test is positive it will form a coloured precipitate
3. The colour of the precipitate changes from blue-green-yellow-orange-brick red
4. The high the conc of reducing sugar the further the colour change will go

Question 17

Explain the Benedict’s test for a non-reducing sugar

Answer 17

1. Add dilute hydrochloric acid to the test solution and heat it in a water bath that’s been brought to the boil
2. Neutralise with sodium hydrogencarbonate
3. Carry out the Benedict’s test for a reducing sugar, if it’s positive a coloured precipitate will form

Question 18

What is a polysaccharide?

Answer 18

A polysaccharide is when more than two monosaccharides are joined together by condensation reactions

Question 19

What is starch?

Answer 19

Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin

Question 20

What is the structure of amylose?

Answer 20

A long, unbranched chain of alpha glucose. The angles of the glycosidic bonds give it a coiled structure, making it compact so it’s good for storage

Question 21

What is the structure of amylopectin?

Answer 21

A long, branched chain of alpha glucose. Its de branches allow the enzymes that break it down to get at the glycosidic bonds easier, meaning glucose can be released quickly

Question 22

Explain the iodine test for starch

Answer 22

Add iodine dissolved in potassium iodide solution to the test sample. If there is starch present, the sample changed from browny-orange to blue-black

Question 23

What is glycogen?

Answer 23

A long, branched chain of alpha glucose. Similar to amylopectin but it has loads more side branches, meaning stored glucose can be released quickly

Question 24

What is cellulose?

Answer 24

A long, unbranched chain of beta-glucose

Question 25

What is the structure of cellulose?

Answer 25

When beta glucose molecules bond they form straight cellulose chains. These chains are linked together by hydrogen bonds to form strong fibres called microfibrils. The strong fibres means cellulose provides structural support for cells