Biological molecules - monosaccharides, disaccharides and polysaccharides

Question 1

Define monomer

Answer 1

The smaller units from which larger molecules are made

Question 2

Define polymer

Answer 2

Molecules made from a large number of monomers joined together

Question 3

Define hexose sugar

Answer 3

Six carbons

Question 4

Define disaccharide

Answer 4

Formed when a pair of monosaccharides combine together

Question 5

What is a condensation reaction?

Answer 5

Molecules joining together by condensation (releases water)

Question 6

What is a glycosidic bond?

Answer 6

A chemical bond formed as the result of condensation between two monosaccharides

Question 7

What is a hydrolysis reaction?

Answer 7

When water is added to a disaccharide under suitable conditions breaks the glycosidic bond releasing the constituent monosaccharides

Question 8

What is a reducing sugar?

Answer 8

A sugar that can donate electrons to (or reduce) another chemical

Question 9

What is a non-reducing sugar?

Answer 9

Disaccharides that do not change the colour of the chemical when they are heated with it

Question 10

What are the monomers present in the disaccharide maltose?

Answer 10

Alpha glucose monomers

Question 11

What are the monomers present in the disaccharide lactose?

Answer 11

Alpha glucose and galactose

Question 12

What are the monomers present in the disaccharide sucrose?

Answer 12

Alpha glucose and fructose

Question 13

Describe how a disaccharide is made

Answer 13

A pair of monosaccharides can combine together to form a disaccharide via a condensation reaction
A glycosidic bond is formed between the pair of monosaccharides
Water is released

Question 14

What type of chain do 1,4 glycosidic bonds form?

Answer 14

Linear chain

Question 15

What type of chain do 1,6 glycosidic bonds form?

Answer 15

Branched chain

Question 16

Describe the structure of starch

Answer 16

• made of alpha glucose
• mixture of amylose and amylopectin
  – amylase has C1 - C4 glycosidic bonds so is unbranched
• amylopectin has C1 - C4 and C1 - C6 glycosidic bond so is branched

Question 17

What is the function of starch?

Answer 17

Energy store in plant cells

Question 18

How does the structure of starch relate to its function?

Answer 18

• helical compact for storage cell
• large polysaccharide molecule, can’t leave cell
• insoluble in water, water potential of cell not affected i.e. no osmotic effect

Question 19

Describe the structure of glycogen

Answer 19

• glycogen is very similar in structure to starch, but has shorter chains and is more highly branched
• it is insoluble
• it is compact

Question 20

What is the function of glycogen?

Answer 20

It is a major carbohydrate storage product of animals

Question 21

How does the structure of glycogen relate to the function?

Answer 21

• highly more branched than starch - has more ends that can be acted simultaneously by enzymes
• it is therefore rapidly hydrolyse to form glucose monomers, which have a higher metabolic rate and respiratory system
• being insoluble - does not diffuse out of cells
• compact - a lot of it can be stored in a small space

Question 22

Describe the structure of cellulose

Answer 22

• made of beta glucose - beta glucose is flipped 180 so that unbranched chains form
• form long, straight, unbranched chains
• parallel strands from microfibrils
• hydrogen bonds link parallel strands together

Question 23

What is the function of cellulose?

Answer 23

Provides strength and structural support to plant cell walls

Question 24

How does the structure of cellulose link to its function?

Answer 24

• cellulose provides support and rigidity because of straight parallel chains of beta glucose - strengthened by hydrogen bonds
• also group to form fibres also adding to the overall strength