Sugars

Question 1

What is sugar a general term for?

Answer 1

• Monosaccharides

* Disaccharides

Question 2

What are monosaccharides?

Answer 2

The simplest sugars, and the building blocks of carbohydrates.

Question 3

What elements do all carbohydrates contain?

Answer 3

• Carbon (C)
• Hydrogen (H)
• Oxygen (O)

Question 4

Are monosaccharides monomers or polymers?

Answer 4

Monomers.

Question 5

What type of monomers are carbohydrates made from?

Answer 5

Monosaccharides.

Question 6

What are some examples of monosaccharides which can form carbohydrates?

Answer 6

• Glucose
• Fructose
• Galactose

Question 7

What type of sugar is glucose?

Answer 7

A hexose sugar.

Question 8

What is a hexose sugar?

Answer 8

A monosaccharide with six carbon atoms in each molecule

Question 9

What are the two types of glucose?

Answer 9

• Alpha (α-glucose)

* Beta (β-glucose)

Question 10

What are α-glucose and β-glucose both?

Answer 10

Isomers.

Question 11

What are isomers?

Answer 11

Molecules with the same molecular formula as each other, but with the atoms connected in a different way.

Question 12

What does α-glucose look like?

Answer 12

Image

Question 13

What does β-glucose look like?

Answer 13

Image

Question 14

How is a disaccharide formed?

Answer 14

When two monosaccharides chemically bond together.

Question 15

How are monosaccharides bonded together?

Answer 15

Through condensation reactions.

Question 16

What type of bond forms when two monosaccharides are bonded together?

Answer 16

A glycosidic bond.

Question 17

How is a glycosidic bond created through a condensation reaction between two monosaccharides?

Answer 17

Two hydroxy groups react with each other, causing a molecule of water to be released, leaving a glycosidic bond.

Question 18

What is a glycosidic bond?

Answer 18

A covalent bond using oxygen.

Question 19

What does a glycosidic bond look like?

Answer 19

Image

Question 20

What does the bonding of two monosaccharides look like (two α-glucose’s)?

Answer 20

Image

Question 21

What are some examples of disaccharides?

Answer 21

• Maltose
• Sucrose
• Lactose

Question 22

How is maltose formed?

Answer 22

When two α-glucose molecules bond together.

Question 23

How is sucrose formed?

Answer 23

When a glucose molecule and a fructose molecule bond together.

Question 24

How is lactose formed?

Answer 24

When a glucose molecule and a galactose molecule bond together.

Question 25

What can all sugar be classified as?

Answer 25

* Reducing sugars | * Non-reducing sugars

Question 26

What is the test for the presence of sugars?

Answer 26

The Benedict's test.

Question 27

What do reducing sugars include?

Answer 27

* All monosaccharides | * Some disaccharides (e.g. maltose and lactose)

Question 28

What is the method of the Benedict's test for reducing sugars?

Answer 28

* Add the Benedict's reagent (blue) to a sample. * Then heat the sample in the water bath (boiled). * Then check for a positive or a negative result.

Question 29

What will a positive result from the Benedict's test for reducing sugars look like?

Answer 29

The sample will form a coloured precipitate, with solid particles suspended in the solution.

Question 30

What are the colours of the precipitates if the Benedict's test for reducing sugars is positive?

Answer 30

* Green * Yellow * Orange * Brick red Image

Question 31

What will a negative result from the Benedict's test for reducing sugars look like?

Answer 31

The sample will stay blue.

Question 32

What does the higher the concentration of reducing sugars present in the Benedict's test mean?

Answer 32

The further the colour change goes.

Question 33

What can you use the colour change from the Benedict's test for reducing sugars to do?

Answer 33

Compare the amount of reducing sugars in different solutions.

Question 34

What are more accurate ways of comparing the amount of reducing sugars from the Benedict's test?

Answer 34

* Filter the solution and weigh the precipitate. | * Remove the precipitate and use a colorimeter to measure the absorbance of the remaining Benedict's reagent.

Question 35

What could there be if the result of the Benedict's test for reducing sugars is negative?

Answer 35

Non-reducing sugars present.

Question 36

What is the test for non-reducing sugars?

Answer 36

By breaking them down into monosaccharides.

Question 37

What is the method for breaking down non-reducing sugars into monosaccharides?

Answer 37

* Get a new sample of the test solution. * Then add dilute hydrochloric acid and heat the sample in a water bath (boiled). * Then neutralise the sample by adding sodium hydrogencarbonate.

Question 38

What is the test for non-reducing sugars, once they are broken down into monosaccharides?

Answer 38

The Benedict's test (the same method as the test for reducing sugars).

Question 39

What will the results of the Benedict's test for non-reducing sugars look like?

Answer 39

* If the sample stays blue, no non-reducing sugar is present. * If a coloured precipitate is formed, non-reducing sugars are present.