3.1.2 Carbohydrates

Question 1

What are the monomers of a carbohydrate called?

Answer 1

Monosaccharides

Question 2

What is a carbohydrate?

Answer 2

A molecule made up of carbon, hydrogen and oxygen

Question 3

What are the three main functions of a carbohydrate?

Answer 3

Energy (for respiration)
Structural (e.g. cell walls)
Storage

Question 4

What is a monomer?

Answer 4

A subunit (individual smaller molecules) that form polymers when put together in chains

Question 5

Give three examples of a monosaccharide.

Answer 5

Glucose, galactose and fructose

Question 6

What type of reaction forms a disaccharide?

Answer 6

Condensation

Question 7

What type of bond is formed in a condensation reaction?

Answer 7

Glycosidic bond

Question 8

How are disaccharides formed?

Answer 8

The condensation of two monosaccharides

Question 9

How is maltose formed?

Answer 9

The condensation of two glucose molecules

Question 10

How is sucrose formed?

Answer 10

The condensation of a glucose and fructose molecule

Question 11

How is lactose formed?

Answer 11

The condensation of a glucose and galactose molecule

Question 12

What are the two isomers of glucose?

Answer 12

Alpha and beta

Question 13

What is the name for a “OH” group?

Answer 13

Hydroxyl group

Question 14

What is the order of the hydroxyl groups in alpha glucose?

Answer 14

Down
Up
Down
Down

Question 15

What is the order of the hydroxyl groups in beta glucose?

Answer 15

Down
Up
Down
Up

Question 16

How are polysaccharides formed?

Answer 16

By the condensation of many glucose units

Question 17

Name two polysaccharide formed by the condensation of alpha glucose?

Answer 17

Glycogen

Starch

Question 18

How is the polysaccharide cellulose formed?

Answer 18

Condensation of beta glucose

Question 19

What’s the general formula of a monosaccharide?

Answer 19

(CH2O)n

Question 20

What makes glucose a hexose sugar?

Answer 20

It has 6 carbon molecules

Question 21

What is the formula of glucose?

Answer 21

C6H12O6

Question 22

Where can cellulose be found?

Answer 22

Cell wall

Question 23

What makes cellulose useful for its function?

Answer 23

Beta glucose is bonded by a condensation reaction to form glycosidic bonds between each unit (alternate upside down upright)
These straight chains of beta glucose are linked by many weak hydrogen bonds which forms a strong bond as there are so many
These form microfibrils which form fibres to make up cellulose
The strength means it’s useful in cell walls because when the cell becomes turgid it won’t burst due to the strength

Question 24

Describe starch?

Answer 24

Alpha glucose
1-4 and 1-6
Energy store 
In plants
Compact
Large surface area

Question 25

Describe glycogen?

Answer 25

``` Alpha glucose 1-4 and 1-6 Energy store In animals Compact Large surface area (branched) Insoluble ```

Question 26

Describe cellulose?

Answer 26

``` Beta glucose 1-4 Makes up cell wall Strong Rigid/flexible In plants ```

Question 27

Why is glycogen useful in animal cells?

Answer 27

Glycogen is branched so glucose can be made at a faster rate More ends are worked on by enzymes simultaneously Animals need more glucose for respiration as they’re more active that plants

Question 28

Name a reducing sugar?

Answer 28

Glucose

Question 29

What is the test for reducing sugars?

Answer 29

Add Benedict’s reagent to the sample Heat the mixture in a water bath until a change is seen Brick-red precipitate indicated the presence of a reducing sugar (Stays blue otherwise)

Question 30

Name a non-reducing sugar?

Answer 30

Sucrose

Question 31

What is the test for a job reducing sugar?

Answer 31

``` Benedict’s reagent to sample Heat in water bath Observe no change (blue) Add hydrochloric acid to sample Heat in water bath Add sodium hydrogencarbonate to the tube Add Benedict’s again Observe a brick red precipitate in the presence of a non-reducing sugar. ```

Question 32

What property of carbon atoms allowed sequences of various lengths to be built?

Answer 32

They readily form bonds with other carbon atoms

Question 33

What is the collective name for carbon containing molecules?

Answer 33

Organic molecules

Question 34

Why is life based on a small number of chemical elements?

Answer 34

In living organisms there are relatively few atoms that attach to carbon

Question 35

In the general formula for a monosaccharide what is the value of n?

Answer 35

Anything from 3 to 7

Question 36

What is a reducing sugar?

Answer 36

A sugar that can donate electrons (or reduce) to another chemical (When tested for they donate to Benedict’s reagent)

Question 37

Why is the bonding of two monosaccharides called a condensation reaction?

Answer 37

A molecule of water is removed

Question 38

What is the hydrolysis of a disaccharide?

Answer 38

Addition of water that causes breakdown into two monosaccharides (under suitable conditions)

Question 39

Why is sodium hydrocarbonate added when testing for non-reducing sugars?

Answer 39

To neutralise the hydrochloric acid previously added which hydrolysed any disaccharides into their monosaccharides

Question 40

What makes polysaccharides suitable for storage?

Answer 40

They are very large molecules which makes them insoluble

Question 41

Where is starch found?

Answer 41

In plants in the form of small granules | Eg starch grains in chloroplasts

Question 42

How is starch tested for?

Answer 42

Add potassium iodide solution Shake or stir Changes blue-black in the presence of starch

Question 43

What is a benefit of starch being insoluble?

Answer 43

It doesn’t affect water potential | So water is not drawn into the cells by osmosis

Question 44

What is the benefit of starch being made of alpha glucose?

Answer 44

When hydrolysed it forms alpha glucose This is easily transported And readily used in respiration

Question 45

Why it the branched form of starch effective is glucose release?

Answer 45

There are more ends More ends can be acted on by enzymes simultaneously Glucose monomers released rapidly

Question 46

Where are the two main places glycogen is stored as small granules?

Answer 46

Muscles | Liver