1 Biological molecules: Carbohydrates

Question 1

What is alpha glucose?

Answer 1

• isomer of glucose
• can bond together to form starch or glycogen

Question 2

What is beta glucose?

Answer 2

• isomer of glucose
• can bond to form cellulose

Question 3

What is cellulose?

Answer 3

• polysaccharide made of beta glucose
• found in plant cells
• beta 1,4 - glycosidic bonds

Question 4

What is a disaccharide?

Answer 4

• made up of 2 sugar units formed by condensation reactions
• monosaccharides joined by glycosidic bonds

Question 5

What is glucose?

Answer 5

• C6H12O6
• single sugar used in respiration

Question 6

What is a hexose sugar?

Answer 6

• sugar made of six carbons
• e.g glucose

Question 7

What is a non reducing sugar?

Answer 7

• a sugar which cannot serve as a reducing agent
• e.g sucrose

Question 8

What is a hydrogen bond?

Answer 8

• a chemical bond formed between positive charge on a hydrogen atom and the negative charge on another atom of adjacent molecule
• often between negative oxygen and positive hydrogen atoms

Question 9

What monosaccharides form disaccharide lactose?

Answer 9

• glucose and galactose
• reducing sugar

Question 10

What monosaccharides form disaccharide sucrose?

Answer 10

• glucose + fructose
• non reducing sugar

Question 11

What monosaccharides form disaccharide maltose?

Answer 11

• glucose + glucose
• reducing sugar

Question 12

What is the structure of starch?

Answer 12

• made up of alpha glucose
• mix of two polysaccharides: amylose and amylopectin

Question 13

What is the structure of amylose?

Answer 13

• long unbranched
• forms coiled/ spring shape

Question 14

What is the structure of amylopectin?

Answer 14

• long and branched due to 1-6 glycosidic bonds

Question 15

What is the structure of glycogen?

Answer 15

• made up of alpha glucose
• long branched chain with lots of side branches ( more than amylopectin)
• glycosidic bonds 1-6

Question 16

What is the structure of cellulose?

Answer 16

• made up of beta glucose
• long unbranched straight chains
• glycosidic bonds 1-4
• chains linked by hydrogen bonds between glucose molecules in each chain to form thicker fibres called microfibrils

Question 17

What are the properties of starch?

Answer 17

• amylose = coiling makes it compact and stores more in a smaller space
• amylopectin = branches increase surface are for enzymes to hydrolyse glycosidic bonds allowing glucose to be released faster

Question 18

What are the properties of glycogen?

Answer 18

• lots of branches increase surface area for enzymes to hydrolyse glycosidic bonds allowing glucose to be released faster
• good compact molecule so good for storage

Question 19

What are the properties of cellulose?

Answer 19

• the hydrogen bonds between cellulose chains make the microfibrils very strong but still flexible allowing them to provide support

Question 20

Uses of starch:

Answer 20

• plants use starch as a way to store excess glucose as it is too large to leave cells and is insoluble
• means it does not affect water potential starch can be hydrolysed to release glucose for respiration

Question 21

Uses of glycogen:

Answer 21

• animals store excess glucose as glycogen in muscles and in the liver
• glycogen is an energy store as it can be hydrolysed to release glucose quickly when needed for respiration e.g exercise

Question 22

Uses of cellulose:

Answer 22

• cellulose is a major structural component in cell walls of plants , it provides support and strength, allowing cells to become turgid