Chapter 5- Lipids

triglycerides (triacylglycerols)

The major form of lipid in food and in the body. They consist of three fatty acids attached to a glycerol molecule.

fatty acids

Organic molecules made up of a chain of carbons linked to hydrogen atoms with an acid group at one end.

phospholipids

Types of lipids containing phosphorous. The most common are the phosphoglycerides, which are composed of a glycerol backbone with two fatty acids and a phosphate group attached.

sterols

Types of lipids with a structure composed of multiple chemical rings.

saturated fatty acid

A fatty acids in which the carbon atoms are to as many hydrogens as possible and which therefore contains no carbon-carbon double bonds.

tropical oils

A term used in the popular press to refer to the saturated oils–coconut, palm, and palm kernel oil–that are derived from plants grown in tropical regions.

monounsaturated fatty acid

A fatty acid that contains one carbon-carbon double bond.

polyunsaturated fatty acid

A fatty acid that contains two or more carbon-carbon double bonds.

omega-3 fatty acid

A fatty acid containing a carbon-carbon double bond between the third and fourth carbons from the omega end.

omega-6 fatty acid

A fatty acid containing a carbon-carbon double bond between the sixth and seventh carbons from the omega end.

trans fatty acid

An unsaturated fatty acid in which the hydrogen atoms are on opposite sides of the double bond.

hydrogenation

The process whereby hydrogen atoms are added to the carbon-carbon double bonds of unsaturated fatty acids, making them more saturated.

phosphoglycerides

A class of phospholipid consisting of a glycerol molecule, 2 fatty acids, and a phosphate group.

emulsifiers

Substances that allow water and fat to mix by breaking large fat globules into smaller ones.

lipid bilayer

Two layers of phosphoglyceride molecules oriented so that the fat-soluble fatty acid tails are sandwiched between the water-soluble phosphate-containing heads.

*lecithin

A phosphoglyceride composed of a glycerol backbone, two fatty acids, a phosphate group and a molecule of choline. *In the body it is a major constituent of cell membranes and is required for their optimal funcition.

cholesterol

A lipid that consists of multiple chemical rings and is made only by animal cells.

*micelles

Particles formed in the small intestine when the products of fat digestion are surrounded by bile acids. They facilitate the absorption of fat.

lipoproteins

Particles containing a core of triglycerides and cholesterol surrounded by a shell of protein, phospholipids, and cholesterol that transport lipids in blood and lymph.

chylomicrons

Lipoproteins that transport lipids from the mucosal cells of the small intestine and deliver triglycerides to other body cells.

lipoprotein lipase

An enzyme that breaks down triglycerides into fatty acids and glycerol; attached to the cell membrane of the cells that line the blood vessels.

very-low-density lipoproteins (VLDLs)

Lipoproteins assembled by the liver that carry lipids from the liver and deliver triglycerides to body cells.

low-density lipoproteins (LDLs)

Lipoproteins that transport cholesterol to cells. Elevated LDL cholesterol increases the risk of cardiovascular disease.

LDL receptor

A protein on the surface of cells that binds to LDL particles and allows their contents to be taken up for use by the cell.

high-density lipoproteins (HDLs)

Lipoproteins that pick up cholesterol from cells and transport it to the liver so that it can be eliminated from the body. A high level of HDL decreases the risk of cardiovascular disease.

adipose tissue

Tissue found under the skin and around body organs that is composed of fat-storing cells.

essential fatty acids

Fatty acids that must be consumed in the diet because they cannot be made by the body or cannot be made in sufficient quantities to meet needs.

eicosanoids

Regulatory molecules, including prostaglandins and related compounds, that can be synthesized from omega-3 and omega-6 fatty acids. *Help regulate blood clotting, blood pressure, and other body processes.

beta-oxidation

The first step in the production of ATP from fatty acids. This pathway breaks the carbon chain of fatty acids into two-carbon units that from acetyl-CoA and releases high-energy electrons that are passed to the electron transport chain.

hormone-sensitive lipase

An enzyme present in adipose cells that responds to chemical signals by breaking down triglycerides into fatty acids and glycerol for release into the blood stream.

cardiovascular disease

Any disease affecting the heart and blood vessels.

essential fatty acid deficiency

A condition characterized by dry scaly skin and poor growth that results when the diet does not supply sufficient amounts of the essential fatty acids. *Rare condition.

atherosclerosis

A type of cardiovascular disease that involves the buildup of fatty material in the artery walls.

atherosclerotic plaque

The cholesterol-rich material that is deposited in the arteries of individuals with atherosclerosis. It consists of cholesterol, smooth muscle cells, fibrous tissue, and eventually calcium.

oxidized LDL cholesterol

A substance formed when the cholesterol in LDL particles is oxidized by reactive oxygen molecules. It is key in the development of atherosclerosis because it contributes to the inflammatory process.

scavenger receptors

Proteins on the surface of macrophages that bind to oxidized LDL cholesterol and allow it to be taken up by the cell.