Topic 1.2/1.3/1.4 - Carbohydrates (mono, di and poly)

Question 1

What are carbohydrates made of?

Answer 1

Carbon, Hydrogen and Oxygen

Question 2

Name 3 monosaccharides

Answer 2

Glucose, fructose and galactose

Question 3

What isomers are there of glucose?

Answer 3

Alpha and Beta

Question 4

Why do we need carbohydrates?

Answer 4

For energy

Question 5

What are the 3 types of carbohydrates?

Answer 5

monosaccharides, disaccharides and polysaccharides

Question 6

What are the 2 polymers of alpha glucose?

/ What are 2 types of starch?

Answer 6

amylose and amylopectin

Question 7

What type of sugar is glucose?

Answer 7

A hexose monosaccharide/sugar

Question 8

What are monosaccharides?

Answer 8

The simplest single sugars

Question 9

How are disaccharides/polysaccharides formed?

Answer 9

Through condensation reactions, where water is removed and is a product,

Question 10

What is the bond that is formed when monosaccharides join together?

Give an example

Answer 10

Glycosidic bond

Alpha glucose joins together to form the disaccharide maltose, it forms a 1-4 glycosidic bond as carbon 1 and carbon 4 bond together (water is then formed as a product)

Question 11

What happens when monosaccharides react with water?

Answer 11

They dissolve to form sweet tasting solutions

Question 12

What happens when polysaccharides/disaccharides break down?

Answer 12

They hydrolyse (water is added)

Question 13

What makes up a disaccharide?

Answer 13

2 monosaccharides

Question 14

What makes up a polysaccharide?

Answer 14

Many monosaccharides

Question 15

What is the structure of amylose?

Answer 15

A chain of glucose molecules that form a helix structure by hydrogen bonding

Question 16

What is the function of the structure of amylose?

Answer 16

The helix forms a compact shape which is good for packaging and therefore making it a good storage molecule

Question 17

What is the structure of amylopectin?

Answer 17

Chains of glucose molecules, after every 25 glucose molecules adjacent chains are connected by alpha 1-6 glycosidic bonds, giving it a BRANCHED STRUCTURE

Question 18

What is the function of the structure of amylopectin?

Answer 18

The branched ends can be hydrolysed rapidly, allowing the rapid release of alpha glucose for energy

Question 19

What are three types of polysaccharide?

Answer 19

Starch, glycogen and cellulose

Question 20

What is the test for reducing sugars (all monosaccharides and some disaccharides, like maltose)?

Answer 20

Benedict’s test

Question 21

For the Benedict’s test, name the colours for the level of concentration of reducing sugars.

Answer 21

No reducing sugars = blue 
Very low concentration = green
Low concentration = yellow
Medium concentration = orange
High concentration = red

Question 22

What is starch used for?

Answer 22

It is the main storage polysaccharide in plants as small grains

Question 23

Where is large amounts of starch found?

Answer 23

In seeds and storage organs

Question 24

How is the structure of starch suited to its function?

Answer 24

Insoluble - does not affect water potential
Large - does not diffuse out of cells
Compact - lots stored in a small space (due to spiral shape)
Branched form has many ends - alpha glucose released rapidly (which is then easily transported and readily used)

Question 25

What is the structure of starch?

Answer 25

Made up of alpha glucose monomers which are joined together through condensation reactions and forms glycosidic bonds.

Question 26

What is glycogen used for?

Answer 26

It is a major storage polysaccharide of animal and fungi cells

Question 27

Where is glycogen usually found?

Answer 27

Muscle and liver

Question 28

What is the structure of glycogen?

Answer 28

Similar to starch, but more highly branched and has shorter chains

Question 29

How is the structure of glycogen suited to its function?

Answer 29

Insoluble - does not draw water in and does not diffuse out of cells Compact - lots can be stored in a small space More highly branched - more enzymes can act on it at once and so rapidly hydrolysed

Question 30

Why might glycogen need to be more highly branched than starch?

Answer 30

Glycogen is found in animal cells, where starch is found in plants. If it is more highly branched, then it can be hydrolysed quicker due to enzymes acting on ends simultaneously, which will support animals higher metabolic rate where it needs more glucose monomers for respiration.

Question 31

What is cellulose used for?

Answer 31

- It is used in cell walls of plants | - For humans, cellulose is also a major source of needed fibre in our diet.

Question 32

What is the structure of cellulose?

Answer 32

It is made up of beta glucose which forms straight and unbranched chains which run parallel to each other

Question 33

What is the function of cellulose?

Answer 33

- Cellulose cell wall prevents cell from bursting (from osmosis) by exerting an inward pressure that prevents influx of water

Question 34

How is the structure of cellulose suited to its function?

Answer 34

- Hydrogen bonds between beta glucose chains add to collective strength - Cellulose groups together to form microfibrils, which in turn are grouped together to form fibrils (all of which provides more strength)

Question 35

What bonds are the glucose chains in cellulose linked by?

Answer 35

Beta 1-4 glycosidic bonds

Question 36

What are the three types of disaccharide?

Answer 36

Maltose, sucrose and lactose

Question 37

What is maltose the product of?

Answer 37

Glucose + Glucose

Question 38

What is sucrose the product of?

Answer 38

Fructose + Glucose

Question 39

What is lactose the product of?

Answer 39

Galactose + Glucose

Question 40

What is the test for starch?

Answer 40

The iodine test

Question 41

How do you conduct a test for non-reducing sugars?

Answer 41

- Add 2cm cubed of food sample to 2cm cubed of hydrochloric acid - Add sodium hydrogencarbonate solution to neutralise HCl - Re-test solution by heating it with 2cm cubed of Benedict's reagent - If there is reducing sugar present, it will turn a certain degree of colour (usually orange/brown)

Question 42

Why must sodium hydrogencarbonate neutralise the HCl in the non-reducing sugars test?

Answer 42

Benedict's reagent does not work in acidic conditions

Question 43

How would you conduct the Benedict's test?

Answer 43

- Add 2cm cubed of food sample - Add 2cm cubed of Benedict's reagent - Heat mixture in a water bath for 5 minutes - If reducing sugars are present it should turn a different colour depending on the concentration of reducing sugars

Question 44

How would you conduct a test for the presence of starch?

Answer 44

- Starch will turn iodine from yellow to blue/black - Add a few drops of a food sample into a spotting tile - Add a drop or two of iodine into each depression - The presence of starch will be indicated when the solution turns black/blue