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Saturated phosphatidylcholine lipids with tails longer than 14 carbons are solid at room temperature, while those with fewer than 14 are liquid. This phenomenon is analogous to the fact that paraffin wax, which is composed of long alkanes, is solid at room temperature, while octane , a short alkane, is liquid.
Animal fats are lipids derived from animals which are used by the animal for a multitude of functions, or can be used by humans for dietary, sanitary, and cosmetic purposes. Depending on the temperature of the fat, it can change between a solid state and a liquid state. Chemically, both fats and oils are composed of triglycerides.
Different lipids can be bought either dissolved in chloroform or as lyophilized lipids. In the case of lyophilized lipids, they can be solubilized in chloroform. Lipids are then mixed with a desired molar ratio. Then chloroform is evaporated using a gentle stream of nitrogen (to avoid oxygen contact and oxidation of lipids) at room temperature.
The lipids with an unsaturated tail (blue) disrupt the packing of those with only saturated tails (black). The resulting bilayer has more free space and is, as a consequence, more permeable to water and other small molecules. At a given temperature a lipid bilayer can exist in either a liquid or a gel (solid) phase.
The term often refers specifically to triglycerides (triple esters of glycerol), that are the main components of vegetable oils and of fatty tissue in animals; [2] or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thus excluding oils.
Most oils are unsaturated lipids that are liquid at room temperature. The general definition of oil includes classes of chemical compounds that may be otherwise unrelated in structure, properties, and uses. Oils may be animal, vegetable, or petrochemical in origin, and may be volatile or non-volatile. [1]
Atomic force microscopy (AFM) has been used in recent years to image and probe the physical properties of lipid bilayers. AFM is a promising technique because it has the potential to image with nanometer resolution at room temperature and even underwater, conditions necessary for natural bilayer behavior.
Structures of some common lipids. At the top are cholesterol [1] and oleic acid. [2]: 328 The middle structure is a triglyceride composed of oleoyl, stearoyl, and palmitoyl chains attached to a glycerol backbone.