Elementary plant Biochemistry and Biotechnology (2+1)

Glycerophospholipids

• The important structural lipid in biological membrane is glycero phospholipid which contains glycerol, fatty acids phosphoric acid and a nitrogenous base.

The general structure of a glycerophospholipid is given below

• Without alcoholic residue (X), it is called as phosphatidic acid
• Depending on the alcoholic residue attached to phosphatidic acid, they are named as
• Phosphatidyl choline (lecithin)
• Phosphatidyl ethanolamine (cephalin)
• Phosphatidyl serine
• Phosphatidyl inositol
• Phosphatidyl glycerol (which include monophosphatidyl glycerol and diphosphatidyl glycerol or cardiolipin).
 
Phosphatidyl choline (lecithin)

• Lecithin contains glycerol, fatty acids, phosphoric acid and a nitrogenous base, choline
• Lecithins are widely distributed in the membranes of cells having both metabolic and structural functions.
• Dipalmityl lecithin is a very effective surface active agent preventing adherence due to surface tension of the inner surfaces of the lungs.
• Most phospholipids have a saturated fatty acid in the C1 position but an unsaturated fatty acid in the C2 position.
 
Phosphatidyl ethanolamine (cephalin)

• The cephalin differs from lecithin only in the nitrogenous group where ethanolamine is present instead of choline

Phosphatidyl serine

• The hydroxyl group of the amino acid L-serine is esterified to the phosphatidic acid
 
Phosphatidyl inositol

• Phosphatidyl inositol is an important constituent of cell membrane phospholipids;
• upon stimulation by a suitable animal hormone it is cleaved into diacylglycerol and inositol phosphate, both of which act as internal signals or second messengers.
 
Phosphatidyl glycerol and diphosphatidyl glycerol (Cardiolipin)

• Cardiolipin is a phospholipid that is found in membranes of mitochondria.
• It is formed from phosphatidylglycerol