1 Biological Molecules- Carbohydrates

Question 1

What are monosaccharides ? + examples

Answer 1

The monomers from which larger carbohydrates are made
e.g.- glucose, galactose, fructose

Question 2

What is a glycosidic bond?

Answer 2

A condensation reaction between 2 monosaccharides

Question 3

What is maltose?

Answer 3

A disaccharide formed by the condensation of 2 glucose molecules

Question 4

What is sucrose?

Answer 4

A disaccharide formed by the condensation of a glucose and fructose molecule

Question 5

What is lactose?

Answer 5

A disaccharide formed by the condensation of a glucose and galactose molecule

Question 6

What is the difference with a-glucose and b-glucose?

Answer 6

They’re isomers, the OH group on the right is on the bottom for a-glucose and on the top for b-glucose

Question 7

What are polysaccharides? + examples

Answer 7

Polymers that are formed by the condensation of many glucose units
e.g.- starch, cellulose, glycogen

Question 8

How are glycogen, starch and cellulose formed?

Answer 8

Starch and glycogen- condensation of a-glucose
cellulose- condensation of b-glucose
glycosidic bond

Question 9

What are the functions of starch?

Answer 9

-The main energy storage material in plants (as compact)
-Broken down into glucose by plants when they need more energy
-Source of food for humans and animals
-Stored in the seeds

Question 10

What are the structures of starch?

Answer 10

-Polymer of a-glucose, a-glycosidic bond
-Twisted chains, form branched molecules
-Compact
-Insoluble in water, so doesn’t change water potential

Question 11

What is the food test for starch?

Answer 11

Add iodine solution to a crushed up food sample
positive result goes from orange to blue-black

Question 12

What are the structures of glycogen?

Answer 12

-Polymer of a-glucose, a-glycosidic bond
-Twisted chain, form branched molecules
-Compact
-Insoluble
-More branched than starch

Question 13

What are the functions of glycogen?

Answer 13

-The main energy storage material in animals (as compact)
- When animals need to release energy, glycogen’s highly branched structure means glucose is quickly released
-When blood glucose levels fall, glycogen is broken down, releasing glucose (glycogenolysis)

Question 14

What are the structures of cellulose?

Answer 14

-Polymer of b-glucose, b-glycosidic bond
-Long, straight, rigid chains, un-branched
-Microfibrils, held by hydrogen bonds

Question 15

What are the functions of cellulose?

Answer 15

-In plant cell walls, offer strength and structural support due to microfibril fibres
-Strength and stability makes it an ideal structural material

Question 16

What is the food test for reducing sugars?

Answer 16

Add Benedict’s reagent to food sample, heat in water bath
positive result is a gradient from brick red, orange and then green

Question 17

What is the food test for non-reducing sugars?

Answer 17

Add hydrochloric acid and boil, then add alkali to neutralise
Add Benedict’s reagent, heat
Positive result is a gradient from brick red, orange and then green