Biological Molecules: Carbohydrates

Question 1

What are monosaccharides?

Answer 1

Monomers of carbohydrates

Question 2

What are some examples of monosaccharides?

Answer 2

glucose, fructose, galactose

Question 3

How are glycosidic bonds formed?

Answer 3

condensation reaction between 2 monosaccharides

Question 4

How are disaccharides formed?

Answer 4

the condensation of 2 monosaccharides

Question 5

How is maltose formed?

Answer 5

condensation of two glucose molecules

Question 6

How is lactose formed?

Answer 6

condensation of glucose and galactose molecules

Question 7

How is sucrose formed?

Answer 7

condensation of glucose and fructose molecules

Question 8

What is a hexose sugar?

Answer 8

monosaccharide with six carbon atoms in each molecule

Question 9

What are isomers?

Answer 9

molecules with the same molecular formula as each other but atoms are connected in different ways

Question 10

How are polysaccharides formed?

Answer 10

condensation reaction of many glucose units

Question 11

How are glycogen and starch formed?

Answer 11

condensation of alpha glucose, this forms glycosidic bonds

Question 12

How is cellulose formed?

Answer 12

condensation of beta glucose

Question 13

What are some examples of disaccharides?

Answer 13

maltose, sucrose, lactose

Question 14

What is a monomer?

Answer 14

smaller units from which larger molecules are made

Question 15

what is the test for (reducing) sugars?

Answer 15

• add Benedict’s reagent and heat using a water bath that has been brought to boil
• if a sugar is present, a coloured precipitate is formed from blue to green, yellow, orange or brick red

Question 16

what is the test for (non-reducing) sugars?

Answer 16

• break down the solution into monsaccharides by adding dilute HCl, then heating the solution using a water bath
• neutralise the solution using sodium hydrogencarbonate
• add benedict’s reagent to the solution and heat using a water bath
• coloured precipitate forms, green, yellow, orange or brick red

Question 17

what are the methods to measure the quantity of reducing sugar?

Answer 17

• remove the precipitate and use a colorimeter (measures the absorbance of remaining benedict’s reagent)
• filter the solution, pat dry the precipitate and weigh the precipitate

Question 18

what are examples of polysaccharides?

Answer 18

starch, glycogen and cellulose

Question 19

what is starch?

Answer 19

a polysaccharide of alpha glucose
- amylose and amylopectin

Question 20

what is amylose?

Answer 20

• long, straight, unbranched chain of alpha glucose
• 1.4 glycosidic bond

Question 21

what is amylopectin?

Answer 21

• long, branched chain of alpha glucose
• 1,4 and 1,6 glycosidic bond

Question 22

what are some properties of starch?

Answer 22

• insoluble in water so it doesn’t affect the water potential
• highly branched = compact and can be easily stored

Question 23

what is glycogen?

Answer 23

polysaccharide of alpha glucose
- branched chain of alpha glucose, joined by glycosidic bonds

Question 24

how does glycogen act as a source of energy?

Answer 24

• hydrolysed to glucose
• glucose is used in aerobic respiration

Question 25

what polysaccharide is the most branched?

Answer 25

glycogen

Question 26

what is cellulose?

Answer 26

polysaccharide formed by the condensation of beta glucose

Question 27

how are cellulose molecules adapted for their function in plant cells?

Answer 27

• cellulose has long and straight chains
• these chains are linked together by hydrogen bonds to form strong fibres called microfibrils
• these microfibrils provide structural support and strength for the cell

Question 28

what is excess glucose stored as?

Answer 28

glycogen

Question 29

what does alpha glucose look like?

Answer 29

• the hydroxyls are both on the bottom

Question 30

what does beta glucose look like?

Answer 30

• the hydroxyls are on opposite sides

Question 31

what does amylose look like?

Answer 31

• angles of the glycosidic bonds gives a coiled structure meaning it is compact and good for storage

Question 32

what does amylopectin look like?

Answer 32

• has side branches which allows enzymes to hydrolyse glycosidic bonds so glucose can be released more easily