100
inside the cell. Proteins also constitute hormones and antibodies, and they influence
gene activity as transcription factors.
Carbohydrates are constituted by molecules comprising carbon, hydrogen, and
oxygen (Horton et al. 1996). They are essential energy source and structural components of cell. Carbohydrates are among the most abundant biomolecules on earth.
Lipids are another key biomolecule inside the cell. They perform a variety of functions, such as serving as a source of stored energy and as chemical messengers in
signal transduction. They are also key component of biological membranes, which
serves as a boundary between cells and their environment and compartmentalizes
cell interior such as the nucleus and the mitochondrion, in eukaryotic organisms.
6.2 What Are Lipids and Oils?
Lipids are basically composed of carbon, hydrogen and oxygen. They are composed
of fatty acid and glycerol. The glycerol backbone and variation in fatty acid chains
as well as their natural modifications resulted into various forms of structural and
functional lipids. These are one of the most important biologically active molecules
that are insoluble in polar solvents but are soluble in non-polar solvents like ether
and chloroform. Lipids are important constituent of living cells. Oils are generally
ester derivatives of glycerol along with three fatty acids. They are important source
of energy, essential fatty acids and fat-soluble vitamins, which have the tendency to
associate with fats. There are various types of lipids and oils that are discussed below.
6.2.1 Phospholipids and Glycolipids
Phospholipids (CH 2 OH-CHOH-CH 2 OH) are amphiphilic molecules that contain
hydrophobic tails (fatty acid chains) and hydrophilic (phosphate group) heads. The
occurrence of a wide variety of phospholipids is due to the variations in head group,
aliphatic chain, and alcohols. Phospholipids, are divided into glycerophospholipids
and sphingomyelins based on the presence of alcohol groups (Baer and Pavanaram
1961). It plays a vital role in the synthesis of lipid bilayer, in drug delivery system,
as components in cosmetics, in biomedical engineering and polymer science, etc.
(Mashaghi et al. 2013).
Glycolipids (C 58 H 95 NO 12 P 2
−2
) are glycosyl derivatives of lipids, which consist of
one or more monosaccharide units bound with glycosidic linkage to a hydrophobic
moiety, e.g. sphingoid, ceramide, and acylglycerol (Malhotra 2012). Glycolipids are
produced in the golgi apparatus and widely distributed in lysosomes, nuclear membrane, mitochondria, and endoplasmic reticulum (Gillard et al. 1993). Glycolipids
have been shown to modulate intracellular activities in signal transduction, cell proliferation, and programmed cell death in lymphoid cells mediated by ceramide.
A. Kumar et al.
inside the cell. Proteins also constitute hormones and antibodies, and they influence
gene activity as transcription factors.
Carbohydrates are constituted by molecules comprising carbon, hydrogen, and
oxygen (Horton et al. 1996). They are essential energy source and structural components of cell. Carbohydrates are among the most abundant biomolecules on earth.
Lipids are another key biomolecule inside the cell. They perform a variety of functions, such as serving as a source of stored energy and as chemical messengers in
signal transduction. They are also key component of biological membranes, which
serves as a boundary between cells and their environment and compartmentalizes
cell interior such as the nucleus and the mitochondrion, in eukaryotic organisms.
6.2 What Are Lipids and Oils?
Lipids are basically composed of carbon, hydrogen and oxygen. They are composed
of fatty acid and glycerol. The glycerol backbone and variation in fatty acid chains
as well as their natural modifications resulted into various forms of structural and
functional lipids. These are one of the most important biologically active molecules
that are insoluble in polar solvents but are soluble in non-polar solvents like ether
and chloroform. Lipids are important constituent of living cells. Oils are generally
ester derivatives of glycerol along with three fatty acids. They are important source
of energy, essential fatty acids and fat-soluble vitamins, which have the tendency to
associate with fats. There are various types of lipids and oils that are discussed below.
6.2.1 Phospholipids and Glycolipids
Phospholipids (CH 2 OH-CHOH-CH 2 OH) are amphiphilic molecules that contain
hydrophobic tails (fatty acid chains) and hydrophilic (phosphate group) heads. The
occurrence of a wide variety of phospholipids is due to the variations in head group,
aliphatic chain, and alcohols. Phospholipids, are divided into glycerophospholipids
and sphingomyelins based on the presence of alcohol groups (Baer and Pavanaram
1961). It plays a vital role in the synthesis of lipid bilayer, in drug delivery system,
as components in cosmetics, in biomedical engineering and polymer science, etc.
(Mashaghi et al. 2013).
Glycolipids (C 58 H 95 NO 12 P 2
−2
) are glycosyl derivatives of lipids, which consist of
one or more monosaccharide units bound with glycosidic linkage to a hydrophobic
moiety, e.g. sphingoid, ceramide, and acylglycerol (Malhotra 2012). Glycolipids are
produced in the golgi apparatus and widely distributed in lysosomes, nuclear membrane, mitochondria, and endoplasmic reticulum (Gillard et al. 1993). Glycolipids
have been shown to modulate intracellular activities in signal transduction, cell proliferation, and programmed cell death in lymphoid cells mediated by ceramide.
A. Kumar et al.