Topic 1.who knows - Carbohydrates

Question 1

What elements are carbohydrates made up of?

Answer 1

Carbon, hydrogen and oxygen

Question 2

What are the three main types of carbohydrates?

Answer 2

Monosaccharides, disaccharides and polysaccharides

Question 3

What are monosaccharides?

Answer 3

Carbohydrates with relatively small molecules

Question 4

What are characteristics of monosaccharides?

Answer 4

Soluble and sweet

Question 5

Give examples of monosaccharides

Answer 5

Ribose
Glucose
Galactose
Fructose

Question 6

What type of sugar is glucose and why?

Answer 6

A hexose bc C6H12O6 (also a reducing sugar)

Question 7

What are isomers?

Answer 7

Same molecular formula but different structural formula

Question 8

What are two isomers of glucose?

Answer 8

Alpha glucose and beta glucose

Question 9

What is the difference between alpha and beta glucose?

Answer 9

The OH attached to C1 is on the bottom in alpha glucose and in beta glucose its on the top

Question 10

What is a reducing sugar?

Answer 10

A substance which when heated with copper sulfate solution the carboxyl group of the sugar reduces copper sulfate to copper oxide and forms a brick red precipitate

Question 11

What test do we use to test for reducing sugars?

Answer 11

Benedict’s test

Question 12

Explain the method of the Benedict’s test

Answer 12

5cm3 of copper sulfate to 10cm3 of test solution. Test tubes placed in boiling bath for 5 mins. Colours compared

Question 13

How does the amount of precipitate formed and the colour relate to the amount of reducing sugar there is?

Answer 13

The greater the concentration of sugar, the greater the colour change and the greater the amount of precipitate formed

Question 14

What is a disaccharide?

Answer 14

Two monosaccharides linked by a glycosidic bond in a condensation reaction

Question 15

Explain the test for non-reducing sugars.

Answer 15

Boil test sample with HCl and then neutralise with sodium hydrogen carbonate until fizzing stops then carry out Benedict’s test. If positive then there are non-reducing sugars

Question 16

How can disaccharides be broken down into their monosaccharides?

Answer 16

Hydrolysis by adding water

Question 17

What is maltose made up of?

Answer 17

Glucose and glucose

Question 18

What is lactose made up of?

Answer 18

Glucose and galactose

Question 19

What is sucrose made up of?

Answer 19

Glucose and fructose

Question 20

Name some reducing sugars

Answer 20

Maltose and lactose

Question 21

Name a non-reducing sugar

Answer 21

Sucrose

Question 22

What are polysaccharides?

Answer 22

Many monosaccharides joined together by glycosidic bonds

Question 23

What are some of the functions of polysaccharides?

Answer 23

Fuel stores and structure

Question 24

What is starch made of?

Answer 24

Amylose and amylopectin

Question 25

What are the similarities between amylose and amylopectin?

Answer 25

They're both isomers of a-glucose

Question 26

What are the differences between amylose and amylopectin?

Answer 26

Amylose forms straight unbranched chains but amylopectin forms branched chains

Question 27

What bonds are in amylose?

Answer 27

1,4 glycosidic bonds

Question 28

What bonds are in amylopectin?

Answer 28

1,4 and 1,6 glycosidic bonds

Question 29

How is a starch molecule stabilised?

Answer 29

Glycosidic bonds keep the helix together and hydrogen bonds stabilise the starch molecules

Question 30

What is the main storage carbohydrate of most plants?

Answer 30

Starch

Question 31

Give some of the useful properties of starch

Answer 31

Insoluble Branched Highly branched so easily hydrolysed

Question 32

What is the test for the presence of starch?

Answer 32

Adding potassium iodide and if it goes from yellow/brown to blue/black then starch is present

Question 33

What is glycogen?

Answer 33

A polymer of a-glucose

Question 34

Where is glycogen found?

Answer 34

Liver and muscle fibres but seen throughout the body apart from the brain

Question 35

When does the body start to metabolise stored fat?

Answer 35

When the glycogen reserves are exhausted

Question 36

What is cellulose?

Answer 36

A polymer of b-glucose held together by B 1,4 glycosidic bonds

Question 37

How does cellulose form fibres?

Answer 37

Chains of b-glucose pack tightly into fibrils which are held together by hydrogen bonds

Question 38

What is cellulose used for?

Answer 38

Plant cell walls

Question 39

Where does the strength of the plant cell walls come from?

Answer 39

From the combined effect of the hydrogen bonds between the chains of b-glucose, the bonds within the chains and the way in which the fibres are arranged in different directions.

Question 40

What are the uses of carbohydrates?

Answer 40

``` Respiration substrate Energy store Structure Transport Cell recognition ```

Question 41

Why can too many carbohydrates lead to obesity?

Answer 41

Carbs are a source of energy More energy in than out means its stored Excess carbohydrates are stored as fats