Biological Molecules 2 - Carbohydrates and Glucose

Question 1

What elements do carbohydrates contain?

Answer 1

Carbon, Hydrogen and Oxygen

Question 2

What are the main functions of carbohydrates?

Answer 2

1.Storage and release of energy
2. Cellular structures

Question 3

How many bonds does each element of carbohydrates form?

Answer 3

Carbon - 4
Oxygen - 2
Hydrogen - 1

Question 4

What is meant by the singular term ‘saccharide’?

Answer 4

It is another term meant for sugar.

Question 5

What are the three classes of carbohydrate?

Answer 5

Monosaccharide - monomers which form the building blocks for larger carbohydrates such as glucose

Disaccharide - 2 monosaccharides joined together by glycosidic bonds during a condensation reaction such as lactose, maltose and sucrose

Polysaccharide - Large complex carbohydrates formed form very large numbers of monosaccharides joined by glycosidic bonds

Question 6

What is the general formula of monosaccharides?

Answer 6

Cn H2n On

Question 7

If n = 3 then the sugar is…

Answer 7

triose

Question 8

If n = 5 then the sugar is…

Answer 8

Pentose

Question 9

Why is glucose considered a hexose sugar?

Answer 9

It has 6 carbons.

Question 10

Draw the structure of alpha glucose, and then the structure of beta glucose.

Answer 10

https://alevelbiology.co.uk/notes/biological-compounds/

Question 11

What is meant by the term isomer?

Answer 11

Molecules which have the same general formula but have different arrangement of atoms such as alpha and beta glucose.

Question 12

What is the difference between alpha and beta glucose?

Answer 12

On carbon 1 of alpha glucose the OH is pointed downwards whereas on beta glucose, the 1st carbon has the OH pointed upwards.

Question 13

What are other examples of hexose monosaccharides other than glucose?

Answer 13

Galactose and Fructose - they are also isomers as they have the same general formula but different arrangement.

Question 14

Do you recognise the structure of fructose and galactose? Try to familiarise yourself with them.

Answer 14

https://stock.adobe.com/uk/images/2d-vector-set-the-molecular-structure-of-the-dietary-monosaccharides-n-glucose-fructose-galactose-molecules-isolated-on-white-background-monosaccharides-simple-sugars-monomers-of-carbohydrates/437754716

Question 15

What is a property of monosaccharides?

Answer 15

They are small in size and soluble in water so they can easily dissolve inside a cell and are easily transported in the bloodstream of animals.

Question 16

Give examples of disaccharides and how they are formed.

Answer 16

Maltose: alpha glucose + alpha glucose

Sucrose: alpha glucose and fructose

Lactose: alpha glucose and galactose

Question 17

Give the main function of each disaccharide.

Answer 17

Maltose: found inside seeds and is an important source of glucose for germination.

Sucrose: transported through the phloem of plants.

Lactose: found in milk and an source of energy for the young.

Question 18

What is the general formula of disaccharides?

Answer 18

C12 H22 O11 (+H2O)

Question 19

What is the resulting link between two sugars called?

Answer 19

A glycosidic bond.

Question 20

What carbon is the glycosidic bond between two monosaccharides?

Answer 20

Carbon 1 of one monosaccharide bonded to carbon 4 of a 2nd.

Question 21

What reaction breaks down disaccharides to monosaccharides?

Answer 21

A hydrolysis reaction chemically inserts water into the bond to break it.

Question 22

Are polysaccharides insoluble and why?

Answer 22

Yes because they are large in size.

Question 23

Why does glucose need to be stored appropriately?

Answer 23

glucose is soluble in water and this can affect osmosis.

Question 24

How is glucose overcome from affecting osmosis?

Answer 24

We can convert glucose to a storage polysaccharide which will give the properties of being insoluble, compact and easily hydrolysed.

Question 25

Give 4 examples of polysaccharides.

Answer 25

Starch, glycogen, chitin and cellulose

Question 26

Briefly describe starch.

Answer 26

Starch is the energy storage in plant cells and is made up of alpha glucose monomers. Starch is also made up of two different molecules: amylose and amylopectin.

Question 27

Describe the structure and bonding of amylopectin

Answer 27

It is a branched polymer It contains alpha 1 - 4 and alpha 1 - 6 glycosidic bonds.

Question 28

Describe the structure and bonding of amylose

Answer 28

It is a straight-chained polymer and it is a helical shape It contains alpha 1 - 4 glycosidic bonds.

Question 29

Briefly describe glycogen.

Answer 29

It is the energy storage in animals and it is very readily hydrolysed. It is also made up of alpha glucose monomers. It is found in muscle and liver cells.

Question 30

Describe the structure and bonding of glycogen.

Answer 30

It is highly branched so that glucose is readily hydrolysed. It contains alpha 1 - 6 and alpha 1 - 4 bonds.

Question 31

Starch and glycogen are made up of alpha-glucose monomers. This means that they have the same structural features as glucose when it is stored correctly in a cell in the appropriate form. Recall the structural features if glucose in a cell.

Answer 31

Insoluble - so doesn't affect osmosis within a cell Compact - so large amounts can be stored in small spaces Readily hydrolysed - to release glucose for respiration.

Question 32

Briefly describe cellulose.

Answer 32

It provides strength and rigidity in plant cell walls and it is made up of beta-glucose monomers. The cellulose cell wall is inelastic and has a high tensile strength to prevent the plant cells from bursting.

Question 33

Describe the structure of cellulose.

Answer 33

each adjacent monomer is rotated by 180 degrees which form straight chains straight chains joined together by hydrogen bonding between OH groups these straight chains formed together by hydrogen binding form a strong microfibril these microfibrils form a strong cellulose bundle the beta-glucose monomers are joined together by alpha 1 - 4 glycosidic bonds

Question 34

Why is cellulose freely permeable

Answer 34

there are spaces between the fibres which means water and solutes can penetrate through to the cell membrane

Question 35

Briefly describe chitin

Answer 35

It is made up of beta-glucose monomers similar in structure to cellulose but some OH groups in each beta-glucose molecule are replaced by nitrogen-containing acetyl amine groups It forms part of an insect's exoskeleton.

Question 36

What are the 3 main features of chitin?

Answer 36

Strong, lightweight and waterproof