3.3 Carbohydrates

Question 1

What is a carbohydrate

Answer 1

A molecule that only contains the elements carbon, hydrogen and oxygen

Question 2

What is the normal elemental ratio of a carbohydrate

Answer 2

Cx(H20)y

Question 3

What is another way of referring to carbohydrates

Answer 3

saccharides or sugars

Question 4

What is a single sugar unit know as

Answer 4

Monosaccharide

Question 5

What are examples of monosaccharides

Answer 5

Fructose, ribose and glucose

Question 6

What is a disaccharide

Answer 6

When two monosaccharides link together

Question 7

What are two disaccharides

Answer 7

Lactose and sucrose

Question 8

What is a polysaccharide

Answer 8

When two or more (usually many more) monosaccharides link together

Question 9

What are examples of polysaccharides

Answer 9

Glycogen, cellulose and starch

Question 10

What is the chemical formula or glucose

Answer 10

C6H12O6

Question 11

What is glucose composed of

Answer 11

6 carbons

Question 12

What is glucose as it has 6 carbons

Answer 12

Hexose monosaccharides

Question 13

What are the two structural variations of glucose

Answer 13

Alpha and beta glucose

Question 14

What is the difference between alpha and beta glucose

Answer 14

The OH (hydroxyl) group are in opposite positions 
In alpha it is at the bottom whereas in beta it is at the top

Question 15

What are some characteristics of glucose

Answer 15

They are polar and soluble in water

Question 16

Why are glucose molecules soluble in water and polar

Answer 16

Due to the hydrogen bonds that form between the hydroxyl groups and water molecules

Question 17

Why is solubility of glucose important

Answer 17

It means that glucose is dissolved in the cytosol of the cell

Question 18

What happens when two alpha glucose molecules are side by side

Answer 18

The two hydroxyl groups interact causing bonds to be broken and new bonds reformed in different places producing new molecules

Question 19

What bond is formed between carbons 1 and 4 on the two alpha glucose molecules that are reacting

Answer 19

1,4 glycosidic bond

Question 20

What is the product of the condensation reaction between two alpha glucose molecules

Answer 20

Maltose and water

Question 21

What is a condensation reaction

Answer 21

When a water molecule is formed as one of the products of a reaction

Question 22

What are two hexose monosaccharides

Answer 22

Fructose and galactose

Question 23

What is fructose often in combination with forming sugar

Answer 23

Glucose forming the disaccharide sucrose

Question 24

What are pentose monosaccharides

Answer 24

Sugars that contain 5 carbon atoms

Question 25

What are two pentose sugars and why are they important

Answer 25

Ribose is present in RNA nucleotides | Deoxyribose is the sugar in DNA

Question 26

How is starch formed

Answer 26

Glucose made by photosynthesis is stored as starch and is made when alpha glucose molecules are joined by glycosidic bonds to form two slightly different polysaccharides collectively known as starch

Question 27

What are the two starch polysaccharides

Answer 27

Amylose and amylopectin

Question 28

How is amylose formed

Answer 28

Formed by alpha glucose molecules joined together by only 1,4 glycosidic bonds

Question 29

What is the shape of amylose

Answer 29

Helix

Question 30

How is amylopectin formed

Answer 30

Also made by 1,4 glycosidic bonds between alpha glucose molecules but also there are some glycosidic bonds formed from the condensation reaction between carbon 1 and 6

Question 31

What is the animal and fungi equivalent energy store to starch

Answer 31

Glycogen

Question 32

Why is having a store of glycogen important

Answer 32

Because animals are mobile unlike plants

Question 33

Why is the coiling/branching of polysaccharides beneficial

Answer 33

It makes them compact for storage. It also means there are free ends where glucose molecules can be added or removed

Question 34

What type of reaction is used to release glucose, starch or glycogen

Answer 34

Hydrolysis reaction | Reverse of a condensation reaction) (adds water molecules

Question 35

How to beta glucose molecules join together

Answer 35

One molecule is flipped so the hydroxyl groups are close enough together to react

Question 36

Why does one beta glucose molecule have to be flipped

Answer 36

Because otherwise the hydroxyl groups on carbon 1 and 4 are too far away from each other to react

Question 37

What sort of chain do two beta glucose molecules form

Answer 37

They form a straight chain molecule called cellulose because it is unable to coil or form branches

Question 38

What is formed when cellulose molecules make hydrogen bonds with each other

Answer 38

Microfibrils

Question 39

What is made when microfibrils join together

Answer 39

Macrofibrils

Question 40

What do macrofibrils combing to produce

Answer 40

Cellulose fibres

Question 41

What is the role of the fibres which are made by macrofibrils

Answer 41

Used to make cells walls

Question 42

What are the properties of the fibres made by macrofibrils

Answer 42

They are strong and insoluble