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Membrane lipids are a group of compounds (structurally similar to fats and oils) which form the lipid bilayer of the cell membrane. The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol. Lipids are amphiphilic: they have one end that is soluble in water ('polar') and an ending that is soluble in fat ...
Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing energy, signaling , and acting as structural components of cell membranes .
In some cases, the hydrated region can extend much further, for instance in lipids with a large protein or long sugar chain grafted to the head. One common example of such a modification in nature is the lipopolysaccharide coat on a bacterial outer membrane.
Many macromolecules are polymers of smaller molecules called monomers. The most common macromolecules in biochemistry are biopolymers ( nucleic acids , proteins , and carbohydrates ) and large non-polymeric molecules such as lipids , nanogels and macrocycles . [ 1 ]
Lipids (oleaginous) are chiefly fatty acid esters, and are the basic building blocks of biological membranes. Another biological role is energy storage (e.g., triglycerides). Most lipids consist of a polar or hydrophilic head (typically glycerol) and one to three non polar or hydrophobic fatty acid tails, and therefore they are amphiphilic.
Polysaccharides (sugar polymers) can be linear or branched and are typically joined with glycosidic bonds. The exact placement of the linkage can vary, and the orientation of the linking functional groups is also important, resulting in α- and β-glycosidic bonds with numbering definitive of the linking carbons' location in the ring.
In the membrane, they can be covalently bound to lipids to form glycolipids or covalently bound to proteins to form glycoproteins. Membranes contain sugar-containing lipid molecules known as glycolipids. In the bilayer, the sugar groups of glycolipids are exposed at the cell surface, where they can form hydrogen bonds. [9]
Lipids are a class of relatively water-insoluble organic molecules, which are the "basic" components of biological membranes. There are three forms of lipids: phospholipids , steroids , and triglycerides .