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?

Blood lipid

Lipid is a broad term for fats and fatty substances in the bloodstream including fatty acids, phospholipids, lipoproteins, triglycerides and cholesterol and other sterols.

Lipids do not dissolve in water, thus move through the bloodstream suspended in protein carriers- lipoproteins. All of these lipoprotein contain phospholipids, triglycerides, and cholesterol but in varying amounts.

Lipids are considered structural, rather than chemical, fats and are important for many body functions, including cell maintenance and repair, dissolving fat-soluble vitamins and other nutrients and storing energy.

High levels of lipid may result from genetic makeup or lifestyle choices or both. Lifestyles factors such as high-fat diet, obesity, smoking, and physical inactivity can cause or contribute to high cholesterol levels, increasing an individual’s risk for atherosclerosis. Cholesterol is an important lipid in the blood.

When the level of lipids in the bloodstream become too high (hyperlipidaemia), lipid droplets can settled out of the blood flow and accumulate along the inner walls of the arteries, forming blockages (occlusions) and eventually compacting into arterial plaque, a brittle layer incorporating other debris such as blood cells that causes the arteries to become stiffened and inflamed.

Abnormalities of blood lipid level are best determined by measurement of the lipoproteins rather than the analysis of the blood lipid fractions alone. Thus disorders on blood lipid level are classified according to the concentration of the lipoproteins.
Blood lipid