3.3 Carbohydrates

Question 1

What elements do carbohydrates contain?

Answer 1

Hydrogen, carbon , oxygen

Question 2

General formula for carbohydrates

Answer 2

Cx (H2O)y

Question 3

What is a monosaccharide

Answer 3

A single sugar unit

Question 4

What is a disaccharide

Answer 4

when 2 monosaccharides link together

Question 5

Examples of monosaccharides

Answer 5

fructose, glucose, ribose, deoxyribose, galactose

Question 6

Examples of disaccharides

Answer 6

maltose, sucrose, lactose

Question 7

What is a polysaccharide

Answer 7

when many monosaccharides link together to form a polymer

Question 8

Examples of polysaccharides

Answer 8

glycogen, cellulose, starch

Question 9

What is the chemical formula for glucose

Answer 9

C6H12O6

Question 10

How many carbons does the monosaccharide glucose contain

Answer 10

6

Question 11

How is glucose a polar molecule

Answer 11

Due to hydrogen bonds that form between hydroxyl groups and water molecules (Oxygen = negative + Hydrogen = positive)

Question 12

What are the two types of glucose?

Answer 12

Alpha
Beta

Question 13

What is the difference between between the two types of glucose?

Answer 13

Order of H and OH is reversed at Carbon-1 on beta glucose
H, OH = alpha
OH, H = beta

Question 14

What is the structure of maltose

Answer 14

2 alpha glucose monosaccharides join together to form a disaccharide

Question 15

What type of reaction is the formation of maltose? Why?

Answer 15

Condensation because water is released when the glycosidic bond forms from the two OH bonds

Question 16

What type of bond forms during the formation of maltose

Answer 16

Glycosidic bond between Carbon-1 and Carbon-4

Question 17

What type of monosaccharides are fructose and galactose

Answer 17

Hexose monosaccharides

Question 18

Where is fructose found

Answer 18

Naturally occurs in fruit

Question 19

What is sucrose made from

Answer 19

Alpha glucose and fructose

Question 20

What is lactose made from

Answer 20

Alpha glucose and galactose

Question 21

Define pentose monosaccharides

Answer 21

sugars that contain 5 carbon atoms

Question 22

Examples of pentose monosaccharides

Answer 22

Ribose and deoxyribose

Question 23

Features of monosaccharides

Answer 23

Monomers
Simplest of sugars (sweet)
Soluble in water (polar so can form H bonds)
Chemical bonds contain a lot of energy (respiratory substrate)

Question 24

Features of disaccharides

Answer 24

made of 2 monomers
tastes sweet
soluble
easily hydrolysed (broken down with water to its monosaccharides)

Question 25

What are isomers

Answer 25

same chemical formula but different structure

Question 26

Define glycosidic bonds

Answer 26

bonds between two monosaccharides and are a type of covalent bond formed by one oxygen from the 2 OH bonds

Question 27

What is starch used for?

Answer 27

Energy store in plants

Question 28

What is glycogen used for?

Answer 28

Energy store in animals

Question 29

What are the two types of starch called?

Answer 29

amylose amylopectin

Question 30

Features of amylose

Answer 30

alpha glucose 1-4 glycosidic bonds twists to form a helix - more compact further stabilised using hydrogen bonds insoluble

Question 31

Features of amylopectin

Answer 31

alpha glucose glycosidic bonds form in condensation reactions (1-6) - more compact branched structure due to 1-6 glycosidic bonds - every 25 units most insoluble

Question 32

Features of glycogen

Answer 32

forms more branches than amylopectin - more compact branching means that there are many free ends where glucose molecules can be added or removed insoluble

Question 33

Why do animals need more glycogen than plants need starch?

Answer 33

Animals are mobile so require more glycogen when the energy is used up faster

Question 34

Why is it important than glycogen has many free ends?

Answer 34

It speeds up process of storing and releasing molecules of glucose

Question 35

Hydrolysis reactions to produce glucose:

Answer 35

Glucose stored until it is needed for respiration To release it, starch or glycogen undergo hydrolysis reactions requiring the addition of water Catalysed with enzymes - reverse of condensation reactions that produce glycosidic bonds

Question 36

Features of cellulose

Answer 36

Insoluble Beta glucose molecules Join together but alternate being inverted to allow them to bond Contain microfibrils

Question 37

How are micro/macro fibrils made?

Answer 37

Hydrogen bonds with each layer of cellulose to form microfibrils which join together to form macrofibrils which combine to make FIBRES

Question 38

Why are fibres important in cellulose of cell walls?

Answer 38

They are strong and essential when making cell walls Also are an important part of our diet

Question 39

Can humans digest beta glucose polysaccharides?

Answer 39

No as we don't have the enzymes required to break them down

Question 40

Why do beta glucose monomers alternate rotating 180 degrees to form glycosidic bonds?

Answer 40

Must rotate 180 degrees so the hydroxyl groups on Carbon 1 and Carbon 4 are close enough to react in a condensation reaction Hydroxyl group is above ring in beta glucose if not inverted (too far away from other OH group)

Question 41

Features of glucose:

Answer 41

Chemical formula C6H12O6 Monosaccharide with 6 carbons (hexose) Polar Soluble in water Respiratory substrate

Question 42

What is sucrose used for?

Answer 42

Form in which carbs are transported in plants Glucose is too useful - would be used up too quickly