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

How are polysaccharides formed?

Answer 9

condensation reaction of many glucose units

Question 10

How are glycogen and starch formed?

Answer 10

condensation of alpha glucose, this forms glycosidic bonds

Question 11

How is cellulose formed?

Answer 11

condensation of beta glucose

Question 12

What are some examples of disaccharides?

Answer 12

maltose, sucrose, lactose

Question 13

What is a monomer?

Answer 13

smaller units from which larger molecules are made

Question 14

what is the test for (reducing) sugars?

Answer 14

• 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 15

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

Answer 15

• 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 16

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

Answer 16

• 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 17

what are examples of polysaccharides?

Answer 17

starch, glycogen and cellulose

Question 18

what is starch?

Answer 18

a polysaccharide of alpha glucose
- amylose and amylopectin

Question 19

what is amylose?

Answer 19

• long, straight, unbranched chain of alpha glucose
• 1,4 glycosidic bond

Question 20

what is amylopectin?

Answer 20

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

Question 21

what are some properties of starch?

Answer 21

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

Question 22

what is glycogen?

Answer 22

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

Question 23

how does glycogen act as a source of energy?

Answer 23

• hydrolyse the glycosidic bonds to release the glucose
• glucose is used in aerobic respiration

Question 24

what polysaccharide is the most branched?

Answer 24

glycogen

Question 25

what is cellulose?

Answer 25

polysaccharide formed by the condensation of beta glucose

Question 26

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

Answer 26

- 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 27

what is excess glucose stored as?

Answer 27

glycogen

Question 28

what does alpha glucose look like?

Answer 28

- the hydroxyls are both on the bottom

Question 29

what does beta glucose look like?

Answer 29

- the hydroxyls are on opposite sides

Question 30

what is the function of amylose?

Answer 30

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

Question 31

why can amylopectin also be a source of glucose?

Answer 31

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

Question 32

how do we test for starch?

Answer 32

- iodine/potassium iodide - solution changes colour from orange brown to blue black

Question 33

what are some properties of glycogen?

Answer 33

- polymer of alpha glucose, so glycosidic bonds can be hydrolysed to glucose whuch is a respiratory substarte required for energy release - branched = compact - branches also means that hydrolysis also takes place at a faster rate - insoluble = doesn't affect the water potential of the cell