3.3 Carbohydrates

Question 1

What elements do carbohydrates contain?

Answer 1

C, H, O

Question 2

What’s another term for a carbohydrate?

Answer 2

Saccharide (sugar)

Question 3

What is a single sugar unit called?

Answer 3

Monosaccharide

Question 4

State the names of the 3 common monosaccharides.

Answer 4

Glucose, fructose, ribose

Question 5

What do 2 linked monosaccharides form?

Answer 5

Disaccharide

Question 6

State the names of the 2 common disaccharides.

Answer 6

Lactose and sucrose

Question 7

What do 2 or more linked monosaccharides form?

Answer 7

Polysaccharides - (Polymer made up of many sugar monomers/monosaccharides)

Question 8

State the names of the 3 common polysaccharides.

Answer 8

Glycogen, cellulose and starch

Question 9

What is the formula for glucose?

Answer 9

C6H12O6

Question 10

What name would you give glucose in the context of its structure?

Answer 10

6-C hexose monosaccharide

Question 11

How are carbons labelled in molecular structure

diagrams?

Answer 11

Clockwise from the oxygen atom

Question 12

What is the property of glucose? Why is this?

Answer 12

Polar + soluble in water - due to H bonds that form between hydroxyl groups + water molecules

Question 13

Why is the solubility of glucose important?

Answer 13

So glucose can be dissolved in the cell cytoplasm

Question 14

What happens when 2 alpha glucose are next to each other?

Answer 14

• 2 hydroxyl groups react w/ each other
• 2 H atoms and 1 O is removed in total from both glucoses and join to form water
• Glycosidic bond forms between carbon 1 of one glucose and carbon 4 of the second glucose, forming 1-4 glycosydic bond

Question 15

Why is the reaction between 2 alpha glucoses a condensation reaction?

Answer 15

Water is produced as a product of the reaction

Question 16

What disaccharide forms when 2 alpha glucose react?

Answer 16

Maltose

Question 17

Give examples of 2 other hexose monosaccharide sugars.

Answer 17

Fructose and galactose

Question 18

Where is fructose naturally found?

Answer 18

Fruit + often with glucose to form sucrose - cane sugar

Question 19

What do you produce when you combine glucose and fructose?

Answer 19

Sucrose, disaccharide

Question 20

What do you produce when you combine glucose and galactose?

Answer 20

Lactose

Question 21

What is lactose? Where is it commonly found?

Answer 21

Lactose is the product of galactose and glucose, commonly found in milk.

Question 22

Compare the sweetness between fructose, glucose and galactose.

Answer 22

Fructose is sweeter than glucose.

Glucose is sweeter than galactose.

Question 23

What are pentose monosaccharides?

Answer 23

5-C sugars

Question 24

State 2 examples of pentose monosaccharides.

Answer 24

Ribose, deoxyribose

Question 25

What's the name of the sugar in RNA nucleotides?

Answer 25

Ribose

Question 26

What's the name of the sugar in DNA nucleotides?

Answer 26

Deoxyribose

Question 27

What is starch?

Answer 27

A polysaccharide formed from alpha glucose molecules joined together

Question 28

In plants, what is glucose stored as?

Answer 28

Starch

Question 29

What is one of the polysaccharides in starch called?

Answer 29

Amylose

Question 30

How is amylose formed?

Answer 30

Amylose is formed by alpha glucose molecules joined together by 1-4 glycosidic bonds

Question 31

What does the angle of the 1-4 glycosidic bond joining amylose mean?

Answer 31

The long glucose chain twists to form a helix, which is further stabilised by H bonding within the molecule

Question 32

Why is the polysaccharide starch less soluble than the glucose molecules used to make it?

Answer 32

The long glucose chain [making up amylose] twists to form a helix, which is further stabilised by H bonding. This makes the molecule more compact, so it's less soluble than glucose.

Question 33

What is the second polysaccharide making up starch, with 1-6 bonds?

Answer 33

Amylopectin

Question 34

What are the 2 polysaccharides that make up starch?

Answer 34

Amylose + amylopectin

Question 35

How is amylopectin formed?

Answer 35

Amylopectin is formed by 1-4 glycosidic bonds between alpha glucose molecules + 1-6 glycosidic bonds (formed by condensation reactions between carbon 1 + carbon 6 of 2 glucose molecules)

Question 36

Why does amylopectin have a branched structure?

Answer 36

Due to 1-6 glycosidic bonds - 1-6 branching points occur every 25 glucose subunits

Question 37

In animals and fungi, what form is glucose stored in?

Answer 37

Glycogen

Question 38

What is glycogen?

Answer 38

A branched polysaccharide formed from alpha glucose molecules + a chemical energy store in animals

Question 39

What's the difference between glycogen and amylopectin?

Answer 39

Glycogen is more branched = more compact + less space needed for it to be stored

Question 40

Besides compaction for storage, what other adaptation is there for the branching of glycogen?

Answer 40

Due to the branching, there are many free ends where glucose can be added or removed - this speeds up the storage/release of glucose

Question 41

What are the key properties of amylopectin and glycogen?

Answer 41

They're insoluble, branched and compact

Question 42

What must happen to glycogen and starch for them to release glucose?

Answer 42

Hydrolysis reactions - the addition of water molecules

Question 43

Why can't beta join together in the same way as alpha?

Answer 43

Hydroxyl/OH groups on carbon 1 and carbon 4 are too far from each other to react

Question 44

What must happen for beta molecules to react?

Answer 44

Second beta must be flipped upside down

Question 45

What polysaccharide is formed when 2 beta join? Describe its structure.

Answer 45

Cellulose - Straight chain, unable to coil or form branches

Question 46

What is formed when cellulose forms H bonds with each other?

Answer 46

Microfibrils

Question 47

What is formed when microfibrils join?

Answer 47

Macrofibrils

Question 48

What is formed when macrofibrils join?

Answer 48

Fibres

Question 49

Describe the properties of the fibres produced when macrofibrils combine, and state what they're used to form?

Answer 49

Strong and insoluble. Used to form cell walls.

Question 50

What type of sugar are glucose, fructose, ribose?

Answer 50

Monosaccharide

Question 51

What kind of sugar are lactose and sucrose?

Answer 51

Disaccharide

Question 52

What type of sugar are glycogen, cellulose and starch?

Answer 52

Polysaccharide