Cholesterol is made up of multiple rings, including three six-carbon rings and one five-carbon ring. This characteristic structure is also seen in steroid hormones and metabolites, as many biologically relevant molecules are derived from cholesterol. Fatty acids are long hydrocarbons (typically between ten and thirty carbons long) with carboxylic acid functional groups on one end. Glycolipids are lipids that have carbohydrate moieties attached, which play a role in cellular and molecular communication. Sphingolipids are a class of lipids that contain a sphingoid base backbone and include sphingosine, sphingomyelin, ceramides, gangliosides and others.

Although it is one of the three main types of membrane lipids (along with phospholipids and glycolipids) cholesterol's structure is quite different. It is a steroid, and so it is made from four linked hydrocarbon rings, including three six-membered rings and one five-membered ring.

Phospholipids are amphipathic, meaning they have an end that is hydrophobic (the fatty acid tail) and an end that is hydrophilic (the head). Phosphate groups have a negative charge, thus attracting them to water, and the presence of a phosphate group at the head of a phospholipid makes that head hydrophilic. Glycerol itself polarizes a fatty acid, but the glycerol is located in the head, not the backbone, and is not charged like phosphate.

Cholesterol is made up of multiple rings, including three six-carbon rings and one five-carbon ring. This characteristic structure is also seen in steroid hormones and metabolites, as many biologically relevant molecules are derived from cholesterol. Fatty acids are long hydrocarbons (typically between ten and thirty carbons long) with carboxylic acid functional groups on one end. Glycolipids are lipids that have carbohydrate moieties attached, which play a role in cellular and molecular communication. Sphingolipids are a class of lipids that contain a sphingoid base backbone and include sphingosine, sphingomyelin, ceramides, gangliosides and others.

Alpha-linolenic acid is an essential fatty acid that must be consumed in the diet (cannot be synthesized by the body). It is an eighteen-carbon omega-3 fatty acid that is used to synthesize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two important long chain polyunsaturated fatty acids. Alpha-linoleic acid is the precursor to arachodonic acid (AA).

Alpha-linolenic acid is an essential fatty acid that must be consumed in the diet (cannot be synthesized by the body). It is an eighteen-carbon omega-3 fatty acid that is used to synthesize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two important long chain polyunsaturated fatty acids. Alpha-linoleic acid is the precursor to arachodonic acid (AA).

Phospholipids are amphipathic, meaning they have an end that is hydrophobic (the fatty acid tail) and an end that is hydrophilic (the head). Phosphate groups have a negative charge, thus attracting them to water, and the presence of a phosphate group at the head of a phospholipid makes that head hydrophilic. Glycerol itself polarizes a fatty acid, but the glycerol is located in the head, not the backbone, and is not charged like phosphate.

Although it is one of the three main types of membrane lipids (along with phospholipids and glycolipids) cholesterol's structure is quite different. It is a steroid, and so it is made from four linked hydrocarbon rings, including three six-membered rings and one five-membered ring.

Double bonds cause unsaturation, thus decreases the melting point. Cis-double bonds as well as methylation also introduce kinks within the chain, decreasing the melting point. Increasing the fatty acid chain length creates saturation, thus causes the melting point to increase. Therefore, decreasing fatty acid chain length has the adverse effect.

The hydrocarbon tail of free fatty acids is nonpolar, and so it interacts unfavorably with water molecules. So, when free fatty acids are placed in a polar environment, the nonpolar tails are driven together and inward in order to avoid water molecules. A micelle is formed from the circular formation of free fatty acids.