1.2, 1.3 & 1.4 Carbohydrates

Question 1

What is a polymer?

Answer 1

Long chains of monomers joined together

Question 2

What is a monomer?

Answer 2

• small, basic molecular units
• eg monosaccharides, amino acids and nucleotides

Question 3

What is an isomer?

Answer 3

• molecules with the same molecular formula as each other but the atoms are connected in different ways
• α-glucose and β-glucose are isomers

Question 4

What is a monosaccharide?

Answer 4

• monomers from which larger carbohydrates are formed
• eg glucose, galactose, fructose

Question 5

What is a hydrolysis reaction?

Answer 5

• breaks a chemical bond between two molecuels
• involved the use of a water molecule

Question 6

What is a condensation reaction?

Answer 6

• joins two molecules together with the formation of a chemical bond
• involved the elimination of water molecule

Question 7

What is a disaccharide?

Answer 7

Pairs of monosaccharides combined by a condensation reaction

Question 8

What is a polysaccharide?

Answer 8

Monosaccharides combined in large numbers

Question 9

How is maltose formed?

Answer 9

A disaccharide formed by the condensation of two glucose molecules

Question 10

How is sucrose formed?

Answer 10

A disaccharide formed by condensation of a glucose and fructose molecule

Question 11

How is lactose formed?

Answer 11

A disaccharide formed by condensation of a glucose and galactose molecule

Question 12

What does the condensation of alpha glucose form?

Answer 12

• glycogen
• starch

Question 13

What does the condensation of beta glucose form?

Answer 13

• cellulose

Question 14

Describe the structure of a starch molecule

Answer 14

• made up of chains of alpha glucose monosaccharides linked by a glycosidic bond
• formed by a condensation reaction
• can be unbranched or branched chains
• unbranched chains wind into a tight coil that makes a molecule very compact

Question 15

Describe the role of starch

Answer 15

• main storage of energy in plants
• store excess glucose as starch ~ when plants need more glucose for energy, it breaks down starch to release glucose
• mixture of two polysaccharides ~ amylose and amylopectin
• insoluble in water ~ doesn’t affect water potential so water cannot enter cells by osmosis

Question 16

Describe the structure of amylose

Answer 16

• long, unbranched chain of alpha glucose
• glycosidic bonds give it a coiled structure = compact
• compact = good for storage because you can fit more in a small space

Question 17

Describe the structure of amylopectin

Answer 17

• long, branched chain of alpha glucose
• side branches allow enzymes that break down the molecule to get to the glycosidic bonds easily
• glucose can be released quickly

Question 18

What is the test for starch and what is the positive result?

Answer 18

• add iodine dissolved in potassium iodide solution to test sample
• positive result = sample changes from red-brown to blue-black

Question 19

Describe the structure of glycogen

Answer 19

• similar to amylopectin BUT has more side branches
• more branches = stored glucose can be released quickly which is important for energy release in animals
• very compact molecule = good for storage

Question 20

Describe the role of glycogen

Answer 20

• main energy storage material for animals
• animals stores excess glucose as glycogen

Question 21

Describe the structure of cellulose

Answer 21

• major component of cell walls in plants
• long, unbranched chains of beta glucose
• beta glucose molecules bond to form straight cellulose chains
• linked together by hydrogen bonds to form strong fibres called microfibrils = these provide structural support to the plant