Part 4 - Lipids The cow milk B-lactoglobulin protein can bind to several lipids among which myristic acid, palmitic acid, stearic acid, and oleic acid. Question 4-1 b) Draw the semi-developed formula of both the palmitic acid and the oleic acid at physiological pH. Circle the hydrophilic part of each molecule. Do not forget to number the carbon atoms.
Lipids
The heterogeneous classes of organic compounds that are not water-soluble but are dissolved in organic solvents that are non-polar in nature are termed lipids. They are a long chain of fatty acids and esters of alcohols. Lipids are generally seen in several plants, microorganisms, and animals. They are utilized as insulation, components of the cell membrane, hormones, and molecules for the storage of energy.
Glycerophospholipid
Glycerophospholipid is the most abundantly occuring phospholipids found in the biological membranes. Lipids include a group of organic compounds like fats, hormones, oils, waxes, vitamins etc. They are non-polar molecules and are insoluble in water. Lipids play an important role in biological systems. They are the building blocks of our cell membranes, store energy and are involved in signaling.
Structure Of Camphor
A terpene with the molecular formula of C10H16O is a waxy, white color solid known as camphor. It is flammable. It also possesses a very pungent taste and a strong odor. There are various sources for extracting camphor from natural products such as the wood of the tree of camphor laurel. Sublimation of wood and steam distillation are some of the methods involved in obtaining camphor.
Glycolipid In Organic Chemistry
Glycolipids are lipids that are an important class of organic compounds in chemistry that have simple to complex applications. They contain carbohydrates, fatty acids, sphingolipids or a glycerol group. In other words, they are the modifications of lipids like acylglycerols, prenols and ceramides. They are all part of a wider group of compounds known as glycoconjugates.
Diterpenoid
The terpenoid class includes diterpenoids, which are chemical compounds with 20 carbon atoms. They are made up of four isoprene units and are derived from geranylgeraniol, a C20 precursor. They have a C20H32 basic structure. These characteristics distinguish diterpenoids from simple terpenes, which have just 10 carbon atoms.
β-Lactoglobulin (BLG) is the major whey protein of cow and sheep's milk (~3 g/l), and is also present in many other mammalian species; a notable exception being humans. Its structure, properties and biological role have been reviewed many times.[1][2][3][4]
Function[edit]
Unlike the other main whey protein, α-lactalbumin, no clear function has been identified for β-lactoglobulin, this despite its being the biggest part of the fractional composition of the globular proteins isolated from whey (β-lactoglobulin ≈ 65%, α-lactalbumin ≈ 25%, serum albumin ≈ 8%, other ≈ 2%). β-lactoglobulin is a lipocalin protein, and can bind many hydrophobic molecules, suggesting a role in their transport. β-lactoglobulin has also been shown to be able to bind iron via siderophores[5] and thus might have a role in combating pathogens. A homologue of β-lactoglobulin is lacking in human breast milk.[6]
Structure[edit]
Several variants have been identified, the main ones in the cow being labelled A and B. Because of its abundance and ease of purification, it has been subjected to a wide range of biophysical studies. Its structure has been determined several times by X-ray crystallography and NMR.[7] β-lactoglobulin is of direct interest to the food industry since its properties can variously be advantageous or disadvantageous in dairy products and processing.[8]
Bovine β-lactoglobulin is a relatively small protein of 162 residues, with an 18.4 kDa. In physiological conditions it is predominantly dimeric, but dissociates to a monomer below about pH 3, preserving its native state as determined by using NMR.[9] Conversely, β-lactoglobulin also occurs in tetrameric,[10] octameric[11] and other multimeric[12] aggregation forms under a variety of natural conditions.
β-Lactoglobulin solutions form gels in various conditions, when the native structure is sufficiently destabilised to allow aggregation.[13] Under prolonged heating at low pH and low ionic strength, a transparent `fine-stranded' gel is formed, in which the protein molecules assemble into long stiff fibres.
β-Lactoglobulin is the main component of milk skin, coagulating and denaturing when the milk boils. Once denatured, the β-Lactoglobulin forms a thin gelatinous film on the surface of the milk.
Folding intermediates for this protein can be studied using light spectroscopy and denaturant. Such experiments show an unusual but important intermediate composed purely of alpha helices, despite the fact that the native structure is beta sheet. Evolution has probably selected for the helical intermediate to avoid aggregation during the folding process.[
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