2.1.2 Biological Molecules – Polysaccharides

Question 1

What is a polysaccharide?

Answer 1

A polymer many of many monosaccharides joined by glycosidic bonds.

Question 2

What 3 features of polysaccharides make them different to monosaccharides?

Answer 2

Made up of many sugar molecules
Insoluble in water
Not sweet
They are not sugars.

Question 3

Which properties of polysaccharides make them good energy stores?

Answer 3

They are…
- Insoluble
- Branching
- Compact
- In chains.

Question 4

Why is it important that polysaccharides are insoluble?

Answer 4

So they do not affect the water potential of the cell.

Question 5

Why is it important that polysaccharides are branches and arranged in chains?

Answer 5

Branched chains are more compact, and allow glucose molecules to be broken off from all ends – releasing glucose quickly for respiration.

Question 6

Why is it important that polysaccharides are compact?

Answer 6

So they do not occupy a lot of space, so can be stored

Question 7

Give 3 examples of polysaccharides

Answer 7

Starch, cellulose, glycogen.

Question 8

Which two polysaccharides make up starch?

Answer 8

Amylose and amylopectin.

Question 9

What are functions of starch?

Answer 9

1) Glucose stored as starch in plant
2) Coil shape makes it compact so doesn’t take up much space
3) Branches can be easily hydrolysed to release energy
4) Starch is a large molecule and so is insoluble in water so has no osmotic effect

Question 10

What is the structure of amylose?

Answer 10

• It is a polymer of alpha glucose and held together by α 1-4 glycosidic bonds
• Amylose coils to form a long compact spiral shape held by H bonds

Question 11

What is the structure of amylopectin?

Answer 11

• It is a polymer of alpha glucose and held together by α 1-4 glycosidic bonds and α 1-6 glycosidic bonds
• It coils to form a spiral shape held by H bonds and has branches from the spiral bonded by α 1-6 glycosidic bonds

Question 12

What is the structure of cellulose?

Answer 12

• It is a polymer of beta glucose and is held together by β 1-4 glycosidic bonds
• It is a straight chain, not branched
• To form other glucose molecule is flipped 180 degrees
• the hydroxyl group have hydrogen bonding
• cellulose is arranged in bundles called microfibrils

Question 13

What is the function of cellulose

Answer 13

1) Microfibril and hydrogen bonds give strength and support so when water moves in it doesn’t burst
2) Microfibrils and hydrogen bonds allow turgidity

Question 14

What is the structure of glycogen?

Answer 14

• It is a polymer of alpha glucose and held together by α 1-4 glycosidic bonds and α 1-6 glycosidic bonds
• It coils to form a spiral shape held by H bonds and has branches from the spiral bonded by α 1-6 glycosidic bonds
• It is shorter and more tightly coiled than starch and has more branches than starch, so more compact

Question 15

What is the function of glycogen

Answer 15

Glucose is stored as glycogen in animals