3.1.2 Carbohydrates

Question 1

Monosaccharides

Answer 1

• Monomers from which larger carbohydrates are made
• Soluble

Question 2

Examples of monosaccharides

Answer 2

• Glucose
• Galactose
• Fructose

Question 3

What does a condensation reaction between 2 monosaccharides form?

Answer 3

Glycosidic bond

Question 4

Disaccharides

Answer 4

2 monosaccharides joined together

Question 5

Examples of disaccharides

Answer 5

• Maltose
• Sucrose
• Lactose

Question 6

Maltose

Answer 6

glucose + glucose

Question 7

Sucrose

Answer 7

glucose + fructose

Question 8

Lactose

Answer 8

glucose + galactose

Question 9

Isomers of glucose

Answer 9

• Alpha glucose
• Beta glucose

Question 10

Formula of glucose

Answer 10

C6H12O6

Question 11

Polysaccharides

Answer 11

• Many monosaccharides joined together
• Large (so insoluble)

Question 12

General formula of monosaccharides

Answer 12

(CH2O)n
n = any number between 3 and 7

Question 13

Types of sugars

Answer 13

• Reducing sugars
• Non-reducing sugars

Question 14

Reducing Sugars

Answer 14

• A sugar that can reduce another chemical (the chemical gains electrons)
• All monosaccharides and some disaccharides

Question 15

Test for reducing sugars

Answer 15

• Benedicts test

1. If food sample is not in liquid form, grind up in water. Filter
2. In test tube, add liquid sample + benedicts reagant
3. Heat in boiling water bath
4. If reducing sugar is present: colour change; blue -> brick red

Question 16

Semi-quantitive use of benedicts reagent

Answer 16

From low to high:
Blue
Green
Yellow
Orange
Orange-brown

Question 17

Non-Reducing sugars

Answer 17

Some disaccharides

Question 18

Test for non-reducing sugars

Answer 18

1. Start with test for reducing sugars. If no colour change, then a reducing sugar is not present.
2. In another test tube, add a fresh liquid sample + dilute HCl.
3. Heat in boiling water bath
4. Retest this solution with the reducing sugars test
5. If non-reducing sugar was present in original sample, it will turn brick-red

Question 19

Why is the reducing sugar test carried out first in the non-reducing test

Answer 19

To make sure no reducing-sugars are present, which would hinder the end result

Question 20

Why was dilute HCl added to the second sample in the non-reducing sugar test

Answer 20

Dilute HCl will hydrolyse the disaccharide into its monosaccharides

Question 21

Test for starch

Answer 21

1. Add iodine to food sample
2. If starch is present, colour change: orange -> blue/black

Question 22

Examples of polysaccharides

Answer 22

• Starch
• Glycogen
• Cellulose

Question 23

Where is starch found

Answer 23

Plant cells

Question 24

What is starch made of

Answer 24

Alpha glucose

Question 25

Characteristics of starch

Answer 25

* Branched or unbranched * Unbranched is wound in tight coil to make molecule compact

Question 26

Role of starch

Answer 26

Important component of food + majot energy source in diets

Question 27

Where is glycogen found

Answer 27

Animal + bacteria cells

Question 28

What is glycogen made of

Answer 28

Alpha glucose

Question 29

Role of glycogen

Answer 29

major carbohydrate storage of animals. very little quantity as fat makes up most of the energy store

Question 30

Comparison of starch and glycogen structure

Answer 30

Glycogen has same structure as starch but shorter chains and more branches

Question 31

Adaptations of starch and glycogen for energy storage

Answer 31

* Insoluble - doesn't affect osmosis * Large + insoluble - doesn't diffuse out of cells * Compact - lots can be stored * Lots of branches - high S.A. for enzyme activity so glucose is released quickly

Question 32

What happens when starch and glycogen is hydrolysed to form glucose

Answer 32

It is readily used in respiration

Question 33

Adaptation of glycogen for energy storage compared to starch

Answer 33

More branches than starch so higher enzyme activity (as animals have high respiration rate)

Question 34

Where is cellulose found

Answer 34

Plant cell walls

Question 35

What is cellulose made of

Answer 35

beta glucose

Question 36

Structure of cellulose

Answer 36

Straight, unbranched chains which are parallel to eachother (hydrogen bonds form cross-linkages between adjacent chains) * The hydrogen bonds are individually weak but collectively strong (good for cell walls) * The cellulose chains are grouped to form microfibrilis -> fibres = more strength

Question 37

Adaptations of cellulose

Answer 37

* Hydrogen bonds for strength + rigidity of cell wall * Microfibrilis for strength