Elementary plant Biochemistry and Biotechnology (2+1)

Glycolipids and sulpholipids and Lipoprotein

Glycolipids and sulpholipids

• Glycolipids are structurally characterised by the presence of one or more monosaccharide residues and the absence of a phosphate.
• They are O-glycoside of either sphingosine or glycerol derivative. The monosaccharides commonly attached are D-glucose, D-galactose or N-acetyl D-galactosamine.
• Monogalactosyl diglycerides and digalactosyl diglycerides have been shown to be present in a wide variety of higher plant tissues
• The 3 position of 1, 2-diacylglycerol is linked to 6- sulpho-6-deoxy D-glucose by an -glycosidic bond in plant sulpholipid
• The predominant fatty acid present in sulpholipid is linolenic acid.
• The sulpholipid is mostly present in chloroplasts, predominantly in the membranes of thylakoid.
• Cerebrosides are composed of a monosaccharide residue glycosidically linked to C-1 of an N-acylated sphingosine derivative.
• The monosaccharide is D-glucose in plants and D-galactose in animals.

Lipoprotein

• Protein molecules associated with triacylglycerol, cholesterol or phospholipids are called lipoproteins.
• Triacylglycerols derived from intestinal absorption or from the liver are not transported in the free form in circulating blood plasma, but move as chylomicrons, as very low density lipoproteins (VLDL) or as free fatty acids (FFA) - albumin complexes.
• Besides, two more physiologically important groups of lipoproteins are low density lipoprotein (LDL) and high density lipoprotein (HDL).
• The major lipid components of chylomicrons and VLDL are triacylglycerol, whereas the predominant lipids in LDL and HDL are cholesterol and phospholipid respectively.
• The protein part of lipoprotein is known as apoprotein.
• Lipoproteins occur in milk, egg-yolk and also as components of cell membranes