Carbohydrates

Carbohydrates

Meaning ' hydrated carbon'
Made up of carbon, oxygen and hydrogen atoms.
Mono-saccharides
1. Mono- means 'one'
2. Glucose Fructose Galactose
  1. There are 2 types of Glucose - Alpha and Beta
    1. They are isomers / the same composition but different arrangement of structure (properties & functions may differ)
      1. The difference is that once it form a ring in the A the C1 OH will point down in the B in will be up.
3. General formula = (CH^2O)n
  1. n = 3-7
4. Simplest of carbohydrates
5. Sweet tasting, soluble substances.
Disaccharides
1. Di- means 'two'
2. Sucrose Maltose Lactose
  1. Reducing sugars
    1. Using water we can 'undo' the glycosidic bond and separate the sugar into 2 monosaccharides (hydrolisis)
  2. Sucrose = glucose & fructose ( 1,4 glycosidic bond)
  3. Lactose = Glucose & Galactose / 1,4 glycosidic bond
3. Formed when 2 monosaccharides react e.g A Glucose + A Glucose = Maltose
  1. The C1 OH & C4 HO react to form H20 and a C-0-C bond (glycosidic bond)
    1. Called 'condensation reaction'
Polysaccharides
1. Poly- means 'many'
2. Cellulose Starch Glycogen
  1. Non-reducing sugars
  2. Starch 2 forms : Amylose / amylopectin
    1. Compact/ insoluble/ Has no osmotic effect / easily broken down by enzymes when required.
      1. 1)Can be stored in smaller spaces
      2. 2)Can be stored in water cells without being used up
      3. 3)No net movement of water as a cause of starch storage - no cells bursting
      4. 4)So plant can quickly respond to changes in glucose levels
    2. Amylose - Simplest form of starch (30%)
      1. 1000's of A-glucose in a straight chain (very tight coils) / insoluble- enzymes only 'nibble' at its ends
    3. Amylopectin (70%)
      1. Every 20 or so = branch of a glucose molecule bonded by a condensation reaction.
        More ends to 'nibble' from = quicker reaction than amylose when there's a glucose deficit
  3. Glycogen: Animal version of Amylopectin
    1. Difference: branch every 6/7 glucose molecule (instead of 20) very compact
      1. Energy store in animal livers
      2. Animals more active - need more energy in shorter amount of time
  4. Cellulose: B-glucose molecules linked by 1,4 glycosidic bonds
    1. Every other glucose is upside down (alternating pattern)
      1. Rigid, straight and compact structure
        many of These end up forming microfibrils of cellulose
        bonded together by hydrogen bonds of adjacent cellulose chains
        H-H bonds are weak but in the masses are quite strong
  5. Starch test : Iodine test
    1. Add iodine dissolved in potassium iodide to sample.
      1. If it turns black-blue there's starch in it.
        If it stays orange there is no starch.
3. Polymers formed from repeated condensation reactions of monosaccharides
Greek prefixes = Mono/Di/Tri/Tetra/Penta/Hexa/Poly
1. Triose= carb with 3 carbons
  1. E.g. Glyceraldehyde
    1. C3H6O3
2. Tetrose = carb with 4 carbons
3. Pentose = 5 carbons
  1. E.g. Ribose
    1. C5H11O5
4. Hexose = 6 carbons
  1. E.g. Glucose
    1. C6H12O6
Ketose group (molecule with C=O bond in the middle of chain)
Aldose= C=O bond at the beggining
Hexoses and pentoses are long enough to form ring structures
1. Glucose: 1) C=O bond breaks 2) C5 loses H and bonds with O instead 3) Broken H bonds with C1
Benedict's Test
1. Heat sample with benedict's reagent
  1. stays blue
    1. No reducing sugars present
      1. Heat new sample with HCL then neutralise with NaHCO3
        Heat with Benedict's reagent
        Goes green , yellow, orange, red or brown
        Non-reducing sugars present
        Stays blue
        No non-reducing sugars present
  2. goes green, yellow, orange, red or brown
    1. Reducing sugars present

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	Created by Julia Romanów about 9 years ago