What are lipids?

Lipids are organic compounds that contain hydrocarbons which are the foundation for the structure and function of living cells.

Lipid molecules contain large hydrocarbon portion and not many polar functional group, which accounts for their solubility behavior. Their intermolecular interactions are dominated by the hydrophobic effect and van der Waals interactions.

Lipids are water insoluble organic compounds. They are hydrophobic (nonpolar) or amphipathic (containing both nonpolar and polar regions)
*Free fatty acids
*Triacylglycerols
*Phospholipids
*Glycolipids
*Steroids

Fatty acids are “carboxylic acids (or organic acid), often with a long aliphatic tails (long chains), either saturated or unsaturated.” When a fatty acid is saturated it is an indication that there are no carbon-carbon double bonds and if the fatty acid is saturated it is an indication that it has at least one carbon-carbon double bond.

Lipids are major components of cell membranes, and are responsible for most of the permeability filter functions of membranes. Membranes act as barriers to separate compartments within eukaryotic cells, and to separate all cells from their surroundings.

A lipid abnormality is one of the causal factors of cardiovascular disease. Excess LDL cholesterol (say a total serum cholesterol > 4-5mmol/L) is the most widely accepted risk factor for heart disease. Excess triglycerides (say >1.8mmol/L) are probably important in CHD but this is controversial. A low concentration of HDL cholesterol (say less than 1.0mmol/L) is also accepted as a major risk factor.
What are lipids?