Organic Materials

  • Organic compounds found in animal and plant body are carbohydrates, lipids, amino acids, proteins, nucleotides, hormones and vitamins.
  • Some of these remain in colloidal form in the aqueous intracellular fluid.
  • Others exist in non-aqueous phases like the lipid membrane and cell walls.

Carbohydrates

  • Carbohydrates are compounds of carbon, hydrogen and oxygen, where the ratio between hydrogen and oxygen is 2:1.

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Monosaccharides

The simplest carbohydrates are monosaccharides, which may be composed of 3 to 7 carbon atoms; they are named as follows:

        • Triose (3C) e.g., Glyceraldehyde
        • Tetrose (4C) e.g., Erythrose
        • Pentose (5C) e.g., Ribose, Deoxy-ribose, Ribulose
        • Hexose (6C) e.g., Glucose, Fructose, Galactose
        • Heptose (7C) e.g., Sedoheptulose

The monosaccharides have either a free aldehyde or ketone group, which can reduce Cu2+ ions to Cu+ ions; they are called reducing sugars.

Oligosaccharides

Oligosaccharides may have two or a few monosaccharides and are named as follows:

    • Disaccharides (2 C): e.g., Sucrose, Maltose, Lactose.
    • Trisaccharides (3 C): e.g., Arabinose, Raffinose
    • Tetrasaccharides (4 C): e.g., Stachyose
    • Pentasaccharides (5 C):e.g., Verbascose

Polysaccharides

  • These are made of hundreds of monosaccharide units.
  • Polysaccharides also called “Glycans“.
  • Long chain of branched or unbranched monosaccharides is held together by glycosidic bonds (1-4 & 1-6 glycosidic bonds)
  • Polysaccharides are insoluble in water and are sweetless.
  • Cellulose is an example built from repeated units of glucose monomer.

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Functions of Carbohydrates

  • Glucose is oxidised to produce energy in living cells.
  • Ribose and deoxyribose form components of nucleotides and nucleic acids.
  • Trioses, tetroses, pentoses and heptoses are the intermediates in the carbon fixation resulting in hexoses.

 

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