Carbohydrates

Monosaccharide general formula= (CH2O)n
1. Soluble
Contain 3 elements
1. Carbon
2. Hydrogen
3. Oxygen
Disaccharides formed in a condensation reaction
glucose+fructose=sucrose
glucose+galactose=lactose
glucose+glucose=maltose
Polysaccharides- insoluble
Starch
1. amylopectin
  1. glucose molecules 1-4 glycosidic bonds, 1-6 after every 25
  2. Branched
  3. Protruding ends= fast hydrolysis --> rapid release of glucose to provide energy via respiration
2. Amylose
  1. 1-4 glycosidic bonds
  2. Hydrogen bonds form a helix
  3. Helix forms a compact shape which allows tight packing so is excellent for storage
3. Insoluble in water so good storage in plants i.e. stoma of chloroplasts
Glycogen
1. Storage in animal and fungal cells
2. Similar structure to amylopectin (polymer of a-glucose)
3. More and shorter branches than amylopectin
  1. More compact
4. Faster hydrolysis than starch, important as animals need emergency glucose faster than plants
Cellulose
1. Structural polysaccharide in plants
2. Long unbranched chains of glucose linked by 1-4 glycosidic bonds
3. Chains linked by hydrogen bonds creating microfibrils
4. Hydrogen bonds prevent water from entering the molecule so it can't be broken down by enzyme hydrolysis= good structural polysaccharide
Carbohydrate tests
1. Starch-Iodine, blue/black precipitate forms
2. Reducing sugar- Benedicts' reagent, brick red ppt. (intensity measured by colorimeter
3. Non-reducimg sugar-benedicts+HCl then NaOH to neutralise. Brick red ppt.

Resource summary

	Created by anna.mat1997 over 10 years ago