Carbohydrates

Question 1

Monosaccharides

Answer 1

• Simplest form of carbohydrates
• One sugar and usually water-soluble, crystalline solids and colourless
• Sweet taste
• (CH2O)n
  Eg
• Glucose
• Fructose
• Galactose
• Ribose

Question 2

Forms of glucose

Answer 2

• A glucose - OH

- B glucose - ^OH

Question 3

Disaccharides

Answer 3

• 2 monosaccharides - condensation reaction
• Glycosidic bond forms
  Eg
• Maltose - 2 alpha glucose
• Sucrose - glucose + fructose
• Lactose - glucose + galactose

Question 4

Polysaccharide

Answer 4

• Multiple condensation reactions between monosaccharides
• Glycosidic bonds
• Range in structure - linear to branched
• Large, insoluble molecule - doesn’t diffuse or affect water potential
  Eg/
  Starch - a glucose molecules - plant storage
  Cellulose - b glucose molecules - structure
  Glycogen - a glucose - body storage

Question 5

Benedict’s Test

Answer 5

• Reducing sugars
• Benedicts agent (blue)
• Blue to red/orange - non-reducing present

Question 6

Chemical formula of glucose

Answer 6

C6H12O6

Question 7

How is glucose used by organisms

Answer 7

Respiration - anaerobic and aerobic + storage in plants

Question 8

What is an isomer

Answer 8

• Same chemical formula but a different structural formula

Question 9

Glycogen

Answer 9

• Glucose is converted into glycogen to stop it transporting around the body

Question 10

Starch

Answer 10

• Polysaccharide - alpha glucose
• Helix - coils = compact
• Glycosidic bonds
• Plant storage + energy source
• Lack of branches = insoluble in water
• Branched = rapid release of energy - ends digested at the same time

Question 11

Insoluble starch

Answer 11

Advantages

• Don’t affect water concentration inside cells - don’t swell or shrink
• Don’t move away from storage areas in plant
• Broken down into glucose - transported around the plant + used in respiration = energy

Question 12

Glycogen

Answer 12

• Polysaccharide - alpha
• Helix - shorter chains than starch
• Many branches = increase solubility
• Animal storage

Question 13

Branched glycogen

Answer 13

• Soluble - transported from one area to another

- Creates lots of ends for enzyme action = release glucose fast

Question 14

Cellulose

Answer 14

• Polysaccharide - beta
• Long straight chains
• Hydrogen bonds = strong layers

Question 15

Cellulose cell walls

Answer 15

• Strongly bonded together by hydrogen bonds
• Strength and support
• Tough layered mesh - keep plants upright + withstand pressure from within the cell
• Cellulose chains = microfibrils

Question 16

Chitin

Answer 16

• Hard, polysaccharide
• Shells of crustaceans
• Cellulose with one hydroxyl group on each monosaccharide replaced by an acetylamine group = increased hydrgoen bonding between adjacent polymers

Question 17

Structural isomer

Answer 17

• Atoms are linked in different sequences

Question 18

Optical isomer

Answer 18

• Atoms are linked in identical ways but are mirror images of each other

Question 19

Explain how the isomeric structure of carbohydrate may affect its chemical behaviour

Answer 19

• Isomeric structure changes how the monosaccharides bond - changes its role in biology

Question 20

2 isomers of glucose; alpha and beta, How do they differ from one another?

Answer 20

• They are the exact same but inverted

Question 21

Describe briefly the process of the condensation reaction for carbohydrates

Answer 21

• H20 is removed

- Disaccharide is produced

Question 22

Describe briefly the process of the hydrolysis reaction for carbohydrates

Answer 22

• Water added

- Form 2 monosaccharides