carbohydrates

Question 1

explain the properties of water

Answer 1

• it has a high melting and boiling point
• the solid is less dense than the liquid
• it has a high surface tension
• it has a high specific heat capacity and specific latent heat

Question 2

explain the hydrogen bonds in water

Answer 2

• they make the water very stable leading to all of its properties

Question 3

explain the food tests for starch

Answer 3

• the iodine test
• add iodine to the sample, if starch is present the iodine will go from orange to blue/black

Question 4

explain the food test for a protein

Answer 4

• the biuret test
• add the solution to the sample, if protein is present it will go from blue to purple

Question 5

explain the food test for a reducing sugar

Answer 5

• using benedicts solution
• add to the sample with water and gently heat over a water bath, if a reducing sugar is present, it will go from blue to red

Question 6

explain the test for a non reducing sugar

Answer 6

• using benedicts solution
• boil sample with HCl and neutralize with an alkali, then add the benedicts and heat gently over a water bath

Question 7

explain the food test for lipids

Answer 7

• the emulsion test
• add equal parts water and ethanol to your sample, shake the sample, if lipids are present it will form a cloudy emulsion

Question 8

explain the test for cellulose

Answer 8

• Schultze solution
• add to the sample, if cellulose is present, it will go from yellow to purple

Question 9

what are monosaccharides and give some examples of monosaccharides

Answer 9

• glucose
• fructose
• galactose
• they are made from one sugar

Question 10

what are disaccharides and give some examples of them

Answer 10

• maltose
• sucrose
• lactose
• they are made from two sugars

Question 11

what are polysaccharides and give some examples of them

Answer 11

• starch
• glycogen
• cellulose
• chitin
• they are made from more than 2 sugars

Question 12

explain the structure of amylose

Answer 12

• alpha glucose molecules joined by a 1,4 glycosidic bond
• forms a helix
• the helix forms a compact shape which allows tight packing
• good storage molecule
• insoluble in water

Question 13

describe the structure of amylopectin

Answer 13

• alpha glucose joined by 1,4 and 1,6 glycosidic bonds
• branched
• has many protruding ends which can be hydrolysed rapidly
• can provide energy during respiration

Question 14

describe the structure of glycogen

Answer 14

• very similar to amylopectin but it has more branches
• the branches are shorter
• more compact than amylopectin, which makes it a good storage molecule

Question 15

describe the structure of cellulose

Answer 15

• beta glucose linked by 1,6 glycosidic bonds
• form long chains
• the parallel chains are linked by hydrogen bonds
• form into strong microfibrils
• hydrogen bonds prevent water from entering the molecule
• structural

Question 16

describe the structure of chitin

Answer 16

• beta glucose
• have an amine group that mineral ions and metal ions can bond to
• contains more hydrogen bonding than in cellulose
• waterproof, strong and lightweight
• resilient and tough