Lipids: Fats, phospholipids, and steriles

Emulsifiers

in foods, substances that allow fat and water to mix. For example, lecithin. It is used as an emulsifier in margarine and baked goods to prevent oil from separating from the other ingredients. In the body, lecithin is a major constituent of cell membranes. It is also used to synthesize the neurotransmitter acetylcholine, which activates muscles and plays an important role in memory.

Fatty Acids

molecules made up of a chain of Carbons linked to Hydrogen, with an acid group at one end of the chain.

Essential Fatty Acids

Fatty acids that are not synthesized by the body therefore must be consumed in the diet such as Omega-3 and Omega-6 fatty acids, in able to meet needs sufficiently.

Phospholipids

Like a triglyceride, a phospholipid has a backbone of glycerol, but it contains two fatty acids rather than three. Instead of the third fatty acid, a phospholipid has a chemical group containing phosphorus, called a phosphate group. The fatty acids at one end of a phospholipid molecule are soluble in fat, while the phosphate-containing region at the other end is soluble in water. Phospholipids act as emulsifiers because they can surround droplets of oil, allowing them to remain suspended in a watery environment. Phospholipids are an important component of cell membranes. They form a double-layered sheet called the lipid bilayer by orienting the water-soluble, phosphate containing "heads" toward the aqueous (water) environments inside and outside the cell and the fatty acid "tails" toward each other to form the lipid center of the membrane.

Micelles

Particles that are formed in the small intestine when the products of fat digestion are surrounded by bile salts. They facilitate the absorption of lipids. In the small intestine, the products of fat digestion and bile form micelles, which move close enough to the brush border to allow lipids to diffuse into the mucosal cells.

Rancidity

Spoilage of fats and oils. Occurs when oxygen damages the unsaturated bonds in fatty acids.

Cholesterol

The best-known sterol is cholesterol. It is needed in the body, but because the liver manufactures it, it is not essential in the diet. More than 90% of the cholesterol in the body is found in cell membranes. It is also part of myelin, the insulating coating on many nerve cells. Cholesterol is needed to synthesize other sterols, including vitamin D; bile acids, which are emulsifiers in bile; cortisol, which is a hormone that regulates our physiological response to stress; and testosterone and estrogen, which are hormones necessary for reproduction. In the diet, cholesterol is found only in foods from animal sources. Plant foods do not contain cholesterol unless it has been added in the course of cooking or processing. Plants do contain other sterols, however, and these plant sterols have a role similar to that of cholesterol in animals: They help form plant cell membranes. Plant sterols are found in small quantities in most plant foods; when consumed in the diet, they can help reduce cholesterol levels in the body.

VLDLs, LDLs, HDLs

The liver can synthesize lipids. Lipids are transported from the liver in very-lowdensity lipoproteins VLDLs. Like chylomicrons, VLDLs are lipoproteins that circulate in the blood, delivering triglycerides to body cells. When the triglycerides have been removed from the VLDLs, a denser, smaller particle remains. About two-thirds of these particles are returned to the liver, and the rest are transformed in the blood into low-density lipoproteins LDLs. LDLs are primary cholesterol delivery system for cells. They contain a higher proportion of cholesterol than do chylomicrons or VLDLs. High levels of LDLs in the blood have been associated with an increased risk for heart disease. For this reason, they are sometimes referred to as "bad cholesterol." Because most body cells have no system for breaking down cholesterol, it must be returned to the liver to be eliminated from the body. This reverse cholesterol transport is accomplished by high-density lipoproteins (HDLs). HDL cholesterol is often called "good cholesterol" because high levels of HDL in the blood are associated with a reduction in the risk of heart disease.

Cis and Trans Fatty Acids

The orientation of hydrogen atoms around the Carbon double bond distinguishes "cis" fatty acids from "trans" fatty acids. Most unsaturated fatty acids found in nature have double bonds in the cis configuration.

Saturated Fatty Acid

a fatty acid in which the carbon atoms are bonded to as many hydrogen atoms as possible; it therefore contains no carbon-carbon double bonds.

Unsaturated Fatty Acid

a fatty acid that contains one or more carbon-carbon double bond; could be either monosaturated containing one double bond or poly saturated containing two or more double bonds.

Lipids

a group of organic molecules, most of which do not dissolve in water. They include fatty acids, triglycerides, phospholipids and sterols.

Chylomicrons

a lipoprotein consisting of triglycerides, along with cholesterol and fat-soluble vitamins, packaged with phospholipids and cholesterol which are formed after long-chain fatty acids (from the digestion of triglycerides) have been absorbed into the mucosal cells and are reassembled into triglycerides.

hydrogenation

a process by which hydrogen atoms are added to the carbon-carbon double bonds of unsaturated fatty acids for the purpose of "synthesizing" a saturated fatty acid. A disadvantage of such a process is that it may convert the fatty acid from a "cys" to "trans" configuration.

Lipoproteins

a water-soluble envelope of protein, phospholipids, and cholesterol form particles called lipoproteins, since long-chain fatty acids, cholesterol, and fat soluble vitamins are not soluble in water and are not absorbed directly into the blood and must be packaged for transport.Different types of lipoproteins transport dietary lipids from the small intestine to body cells, from the liver to body cells, and from body cells back to the liver for disposal.

Linoleic Acid (Omega-6)

an essential polyunsaturated fatty acid which is characterized by its location of the first double carbon bond between the sixth and seventh Carbons on the omega side of the chain. such as arachidonic acid. They help stimulate skin and hair growth, maintain bone health, regulate metabolism, and maintain the reproductive system. Omega-6 fatty acids play a crucial role in brain function, as well as normal growth and development.

Alpha-Linoleic Acid (Omega-3)

an essential polyunsaturated fatty acid which is characterized by the location of the first double carbon bond between the third and fourth carbon on the omega side of the chai; CH3. Such as Eicosapentanoic acid;EPA and docosahectanoic acid;DHA found in fatty fish. Research shows that omega-3 fatty acids reduce inflammation and may help lower risk of chronic diseases such as heart disease, cancer, and arthritis. Omega-3 fatty acids are highly concentrated in the brain and appear to be important for cognitive (brain memory and performance) and behavioral function.

Tropical Oils

saturated plant oils, found in plants found in tropical climates including; palm oil, palm kernel oil, coconut oil. They are useful in food processing because they are less susceptible to spoilage than are more unsaturated oils.

Triglycerides

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

Phospholipids

types of lipids whose structure includes a phosphorous atom. Makes up most animal cell plasma membrane.

Sterols

types of lipids with a structure composed of multiple chemical rings such as cholesterol which aide in many process of cellular activities including membrane structure,permeability, and fluidity. Ergosterol which is found mostly in fungi membrane and also serves a similar function and a provitamin for vitamin D2, and Beta sitosterol; a phytosterol;plant sterol