1.2 Carbohydrates

Question 1

Draw an alpha glucose molecule

Answer 1

Question 2

Draw a beta glucose molecule

Answer 2

Question 3

Acronym to rememebr position of hydroxyl group on 1st carbon atom of glucose isomers

Answer 3

ABBA (Alpha below , beta above )

Question 4

What type of sugars are all monosachharides

Answer 4

Hexose

Question 5

Name the 3 monosacharides

Answer 5

• Glucose
• Fructose
• Galactose

Question 6

Name the 3 diasachharides, and what monosaccharides form them

Answer 6

• Maltose - alpha glucose + alpha glucose
• Sucrose - alpha glucose + fructose
• Lactose - alpha glucose + galactose

Question 7

Describe the reaction, turning a monosaccharide into a disaccharide

Answer 7

• Condensation reaction between monosacharides
• Glycosidic bond formed
  * Loss of a water molecule

Question 8

Where does a glycosidic bond form between monosaccharides

Answer 8

2 hydroxyl groups

Question 9

Describe the reaction turning disaccharides into polysaccharides

Answer 9

• Conensation reaction between many disaccharides
• Many glycosidic bonds formed
• Many water molecules released

Question 10

What are the polymers of alpha glucose

Answer 10

Starch and glycogen

Question 11

What are the polymers of beta glucose

Answer 11

Cellulose

Question 12

Describe how starch’s structure, makes it a useful storage molecule

Answer 12

• Polysaccharide and polymer of alpha-glucose, with 1,4 glycosidic bonds between glucose molecules - can provide respiratory substrate to release energy
• Coiled helix shape - compact, so more can be held in the cell
• Insoluble - no effect on water potential
• Large - cannot leave cell by cell-surface membrane
• Branched with 1,6 glycosidic bonds - glucose can be hydrolysed rapidly for respiration

Question 13

Describe how glycogen’s structure makes it a useful storage molecule

Answer 13

• Polysaccharide and polymer of alpha glucose, with 1,4 glycosidic bonds between glucose molecules - can provide respiratory substrate to release energy
• Spherical - compact so more can be stored in cell
• Insoluble - no effect on water potential
• Large - cannot leave cell by cell-surface membrane
• Branched with 1,6 glycosidic bonds - glucose can be hydrolysed rapidly for respiration

Question 14

Describe how cellulose’s strucutre, relates to it’s function

Answer 14

• Polysaccharide and polymer of beta-glucose, with 1,4 glycosidic bonds between glucose molecules
• Every other glucose molecule inverted - results in linear-chain
• Microfibrils and fibrils form as hydrogen bonds form between adjacent chains - provides strength and allows cell wall to be flexible

Question 15

Similarities between starch, glycogen and cellulose

Answer 15

• Polysaccharides
• Polymer of glucose
• Contain Carbon, hydrogen and oxygen
• Have 1,4 glycosidic bonds

Question 16

Points of comparison for polysaccharides

Answer 16

• Type of glucose
• Shape
• Branching
• 1,6 glycosidic bonds
• Microfibrils

Question 17

Describe the test for starch

Answer 17

• Add iodine solution
• If positive, will turn blue-black
• If negative, will stay orange

Question 18

Describe the test for reducing sugars

Answer 18

• Crush/grind sample, and add water to form solution
• Add equal volume of Benedict’s solution
• Place in hot water bath at 85c and heat for 5mins
• If positive will be brick-red
• If low levels, will be orange/yellow/green
• If negative will turn blue

Question 19

Describe the test for non-reducing sugars

Answer 19

• Crush/grind sample, then add water to form a solution
• Boil with hydrochloric acid
• Neutralise with sodium bicarbonate
• Add Benedict’s solution
• Heat at 85c for 5mins
• If positive, will turn brick-red
• If low levels will turn orange/yellow/green
• If negative, will turn blue