🩷 3.1.2 Carbohydrates

Question 1

What are monosaccharides ?

Answer 1

They are the monomers from which larger Carbohydrates are made from.

Question 2

Give 3 examples of monosaccharides.

Answer 2

Glucose, galactose and fructose

Question 3

What is formed when a condensation reaction occurs between 2 monosaccharides?

Answer 3

A glycosidic bond is formed.

Question 4

What is formed by the condensation of two monosaccharides?

Answer 4

A disaccharide is formed.

Question 5

Name 3 disaccharides .

Answer 5

Maltose, sucrose and lactose

Question 6

What is maltose formed from?

Answer 6

A condensation reaction between two glucose molecules

Question 7

What is sucrose formed from?

Answer 7

A condensation reaction between a glucose molecule and a fructose molecule.

Question 8

What is lactose formed from ?

Answer 8

A condensation reaction between a glucose molecule and a galactose molecule.

Question 9

What is an isomer?

Answer 9

A molecule that has the same formula but a different arrangement of atoms.

Question 10

What are the isomers of glucose?

Answer 10

Alpha glucose and beta glucose

Question 11

How are polysaccharides formed?

Answer 11

By the condensation of many glucose units

Question 12

What is glycogen formed from?

Answer 12

The condensation of alpha glucose

Question 13

What is glycogen used as in animals?

Answer 13

It stores excess glucose as glycogen

Question 14

What is starch formed from?

Answer 14

The condensation of alpha glucose

Question 15

What is starch used as in plants?

Answer 15

It stores excess glucose as starch

Question 16

What is cellulose formed from?

Answer 16

The condensation of beta glucose

Question 17

What is cellulose used as in plants?

Answer 17

It is found in the cell wall of a plant and is used for structural support for a cell.

Question 18

Give some structures of glycogen.

Answer 18

• Highly branched
• 1,4 and 1,6 glycosidic bonds
• compact molecule
• insoluble
• Large

Question 19

why is being highly branched good functionally ?

Answer 19

Easily and quickly hydrolysed to release glucose for respiration to make ATP.

Question 20

Why is being compact good functionally ?

Answer 20

It is good for storage.

Question 21

Why is being insoluble good functionally ?

Answer 21

It doesn’t impact the water potential of a cell.

Question 22

Why is being large good functionally?

Answer 22

It cant leave the cell.

Question 23

Where is glycogen stored?

Answer 23

In animals and fungi.

Question 24

Give some structures of cellulose.

Answer 24

• Long, straight chains
• Insoluble
• Folded
• each chain is inverted after each alternate chain to form the 1,4 glycosidic bonds

Question 25

Many cellulose chains linked together with many hydrogen bonds is called...

Answer 25

A microfibrill

Question 26

What is the functional benefit of microfibrills ?

Answer 26

They confer strength to the cellulose which helps support the cell.

Question 27

What is the functional benefit of them being folded?

Answer 27

They are compact so good for storage

Question 28

Cellulose is permeable. Why is this good?

Answer 28

It allows substances to reach the cell membrane.

Question 29

Where is cellulose found?

Answer 29

In plants

Question 30

Give some structures of starch.

Answer 30

- Coiled/helical - mixture of 2 polysaccharides: Amylose (unbranched) Amylopectin (branched) - Insoluble

Question 31

What is the functional benefit of being coiled/helical?

Answer 31

It is compact and can fit in the cell.

Question 32

Where is starch found?

Answer 32

It is found in a plant.

Question 33

What is the test for starch ?

Answer 33

Add iodine to the test. If it is present then there is a colour change from brown/orange to bluey black.

Question 34

What is the biochemical test for reducing sugars ?

Answer 34

1- Boil solution in a water bath till it reaches 100 degrees 2- Add benedicts reagent to the solution 3- A positive test is a change from blue to brick red precipitate

Question 35

What are some things that the reducing sugar test can test for ?

Answer 35

- All monosaccharides - maltose - lactose

Question 36

What is the biochemical test for non reducing sugars ?

Answer 36

1- Do the reducing sugar test first. If it remains blue (no change) then discard test and do the non reducing test. 2- Boil substrate with dilute HCL in a water bath 3- Neutralise it with some kind of alkaline (e.g. sodium hydrogen carbonate) 4- Add benedicts reagent 5- Heat in a water bath 6- A change from blue to red precipitate is a positive result.

Question 37

What are some things that the non reducing sugar test can test for ?

Answer 37

sucrose