Monosaccharides

Question 1

What are the functions of carbohydrates?

Answer 1

Food energy source
Store energy (starch = plants, glycogen = animals)
Flavouring (simple sugars are sweet)
Functional ingredients (sucrose allows ice cream to be soft)

Question 2

What is the general formula for a carbohydrate?

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

Two monosaccharides

Question 5

What is a oligosaccharide?

Answer 5

Three-ten monossacharides

Question 6

What is a polysaccharide?

Answer 6

Ten or more monossacharides

Question 7

What is a polyalcohol?

Answer 7

Sugars containing a hydroxyl group attached to each carbon

Question 8

What is a triose sugar and what is its formula?

Answer 8

A sugar containing three carbons

C3H6O3

Question 9

What is an aldose- sugar?

Answer 9

Contains an aldehyde group ( C = O at the end)

Question 10

What is a ketose- sugar?

Answer 10

Contains a ketone group ( C = O in the middle)

Question 11

How many stereoisomers does a molecule with ‘n’ chiral centres have?

Answer 11

2^n

Question 12

What are enantiomers and how are they named?

Answer 12

Compounds related by inverting configuration at all chiral centres (mirror image)
L- and D-

Question 13

What are diastereomers and how are they named?

Answer 13

Compounds related by inverting configuration at one or more chiral centres (NOT ALL)
Completely different name

Question 14

What are epimers and how are they named?

Answer 14

Diastereomers with an inverted configuration at one asymmetric carbon
Completely different names

Question 15

What are the stereoisomers of glucose?

Answer 15

Anomers

• Alpha = OH below H
• Beta = OH above H

Question 16

What is mutarotation?

Answer 16

Switching back and forth between a ring and straight chain structure

Question 17

What are aldehydes easily oxidised to and what does that mean about the molecule?

Answer 17

Carboxylic acid

It is a reducing sugar

Question 18

Are ketones easily oxidised and what does this say about the molecule?

Answer 18

No

It is a non-reducing sugar

Question 19

When do reducing sugars undergo the Maillard reaction and what does it produce?

Answer 19

When they are in the presence of amino acids

Produces colour and flavour

Question 20

What is glucose full name?

Answer 20

a-D-glucopyronase

• a because OH is below H on anomeric carbon
• Pyranose because it is a 6 membered ring

Question 21

What is fructose full name?

Answer 21

B-D-fructofuranose

• B because OH is above H on anomeric carbon
• Furanose because it is a 5 membered ring

Question 22

What sugar is the only common ketose?

Answer 22

Fructose

Question 23

What is the sweetest natural sugar?

Answer 23

Fructose

Question 24

Where is galactose found?

Answer 24

In milk products after lactose hydrolysis

Question 25

What is the most common pentose sugar?

Answer 25

Ribose

Question 26

What is the dietary source of ribose?

Answer 26

Meat, fish and poultry

Question 27

How is the disaccharide maltose formed?

Answer 27

By a hydrolysis reaction between the hemiacetal group on one D-glucopyranose and the OH of another

Question 28

How are disaccharides named?

Answer 28

1. Configuration of the anomeric carbon of the first sugar (alpha or beta) 2. The name of the first sugar (aldehyde / ketose and furanose / pyranose) 3. The numbers of the carbon atoms involved in the bond and the direction of the bond ( 1 - 4, 1 - 5 ) 4. The name of the second sugar in the same manner as the first

Question 29

How is sucrose formed and is it a reducing sugar?

Answer 29

Between glucose and fructose - Head to head (1 - 2) - Non reducing sugar because there is no free anomeric carbon

Question 30

Where is sucrose formed?

Answer 30

Only in plants

Question 31

Name two sources of sucrose.

Answer 31

Sugar beet | Sugar cane

Question 32

How is lactose formed and is it a reducing sugar?

Answer 32

Between glucose and galactose - Head to tail (1 - 4) - Reducing sugar as it has a free anomeric carbon

Question 33

What is the main source of natural galactose?

Answer 33

Milk

Question 34

How is trehalose formed and is it a reducing sugar?

Answer 34

Between glucose and glucose - Head to head (1 - 1) - Non reducing because there is no free anomeric carbon

Question 35

What are the functions of trehalose?

Answer 35

- Energy storage in insects - Protects organisms against stress (dry, freezing, salt stress) - Moisture retaining (used in moisturisers) - Preserves tissues and proteins (used in organ transplant solutions) - Used in genetic modification (cloned into plants to make them drought resistant)

Question 36

How is maltose formed and is it a reducing sugar?

Answer 36

Between glucose and glucose - Head to tail (1 - 4) - Reducing sugar because it has a free anomeric carbon

Question 37

How is cellobiose formed and is it a reducing sugar?

Answer 37

Between glucose and glucose - Head to tail (1 - 4) - Reducing sugar because it has a free anomeric carbon

Question 38

How are sugar alcohols produced?

Answer 38

By the hydrogenation of sugars

Question 39

What are the properties of sugar alcohols?

Answer 39

Few calories | Very small blood glucose and insulin response

Question 40

What are the uses of sugar alcohols?

Answer 40

Gums | Toothpastes

Question 41

What does non cariogenic mean?

Answer 41

Do not cause tooth decay

Question 42

What sugar alcohols produce a cooling sensation?

Answer 42

Xylitol and sorbitol

Question 43

What are the properties of oligosaccharides?

Answer 43

Soluble | Not digested by human enzymes

Question 44

Where are oligosaccharides found?

Answer 44

In artichokes and chicory