Chapter 5 The Lipids: Triglycerides, Phospholipids, and Sterols

lipids

a family of compounds that includes triglycerides, phospholipids, and sterols. lipids are characterized by their insolubility in water

fatty acids

organic compounds composed of carbon chains with hydrogen attached

monounsaturated fatty acid

a fatty acid that lacks two hydrogen atoms and has one double bond between carbons (MUFA)

point of unsaturation

the double bond of a fatty acid, where hydrogen atoms can easily be added to the structure

polyunsaturated fatty acid

a fatty acid that lacks four or more hydrogen atoms and has two or more double bonds between carbons (PUFA)

saturated fatty acid

a fatty acid carrying the maximum possible number of hydrogen atoms

unsaturated fatty acid

a fatty acid that lacks hydrogen atoms and has at least one double bond between carbons

linoleic acid

an essential fatty acid with 18 carbons and two double bonds

linolenic acid

an essential fatty acid with 18 carbons and three double bonds

omega

refers to the position of the closest double bond to the methyl end of a fatty acid

omega-3 fatty acid

a polyunsaturated fatty acid in which the closest double bond to the methyl end of the carbon chain is three carbons away

omega-6 fatty acid

a polyunsaturated fatty acid in which the closest double bond to the methyl end of the carbon is six carbons away

triglycerides

the chief form of fat in the diet and the major storage form of fat in the body. each triglyceride is composed of a molecule of glycerol with three fatty acids attached

glycerol

an alcohol composed of a three-carbon chain, which can serve as the backbone for a triglyceride

hydrogenation

a chemical process by which hydrogens are added to monounsaturated or polyunsaturated fatty acids to reduce the number of double bonds, making the fats more saturated (solid) and more resistant to oxidation (protecting against rancidity)

margarine

a butter substitute made primarily of hydrogenated vegetable oils and sometimes blended with animal fats, emulsifiers, water, milk salt, vitamins, artificial color, and other ingredients

cis

on the near side of; refers to a chemical configuration in which the hydrogen atoms are located on the same side of a double bond

trans

on the other side of; refers to a chemical configuration in which the hydrogen atoms are located on opposite sides of a double bond

trans-fatty acids

fatty acids with hydrogens on opposite sides of the double bond

conjugated linoleic acids

several fatty acids that have the same chemical formula as linoleum acid but with different configurations

phospholipid

a compound similar to a triglyceride but having a phosphate group and chlorine in place of one of the fatty acids

lecithin

one of the phospholipids. both nature and the food industry use lecithin as an emulsifier to combine water-soluble and fat-soluble ingredients that do not ordinarily mix, such as water and oil

choline

a nitrogen-containing compound found in foods and made in the body from the amino acid methionine. choline is a part of the phospholipid lecithin and the neurotransmitter acetylcholine

hydrophobic

a term referring to water-fearing, or non-water soluble, substances

hydrophilic

a term referring to water-loving, or water-soluble, substances

emulsifiers

substances with both water-soluble and fat-soluble portions that enable oils and fats to mingle in watery solutions

sterols

compounds containing a four-ring carbon structure with any of a variety of side chains attached

cholesterol

one of the sterols containing a four-ring carbon structure with a carbon side chain

endogenous

arising within the body

exogenous

arising outside the body

plaque

an accumulation of fatty deposits, smooth muscle cells, and fibrous connective tissue that develops in the artery walls in atherosclerosis

atherosclerosis

a type of artery disease characterized by plaques on the inner walls of the arteries

lipases

enzymes that hydrolyze lipids

monoglycerides

molecules of glycerol with one fatty acid attached

micelles

tiny spherical complexes of emulsified fat that arise during digestion; most contain bile salts and the products of lipid digestion, including fatty acids, monoglycerides, and cholesterol

lipoproteins

clusters of lipids associated with proteins that serve as transport vehicles for lipids in the lymph and blood

chylomicrons

lipoproteins that transport lipids from the intestinal cells to the rest of the body

VLDL (very-low-density lipoproteins)

lipoproteins made by the liver that transport lipids from the liver to other tissues

LDL (low-density lipoproteins)

lipoproteins that derive from VLDL and transport lipids in the blood

HDL (high-density lipoproteins)

lipoproteins that help remove cholesterol from the blood by transporting it to the liver for reuse or disposal

adipose tissue

the body’s fat tissue; consists of masses of triglyceride-storing cells

adipokines

proteins synthesized and secreted by adipose cells

resistin

a protein produced by adipose cells that promotes inflammation and causes insulin resistance

adiponectin

a protein produced by adipose cells that inhibits inflammation and protects against insulin resistance, type 2 diabetes, and cardiovascular disease

essentail fatty acids

fatty acids that the body requires but cannot make, and so must be obtained from the diet; both linoleum acid and linolenic acid are essential fatty acids

arachidonic acid

an omega-6 polyunsaturated fatty acid with 20 carbons and four double bonds; present in small amounts in meat and other animal products and synthesized in the body from linoleum acid

conditionally essential nutrient

a nutrient that is normally nonessential, but must be supplied by the diet in special circumstances when the need for it exceeds the body’s ability to produce it

eicosapentaenoic acid

an omega-3 polyunsaturated fatty acid with 20 carbons and five double bonds; present in fatty fish and synthesized in limited amounts in the body from linolenic acid

docosahexaenoic acid

an omega-3 polyunsaturated fatty acid with 22 carbons and six double bonds; present in fatty fish and synthesized in limited amounts in the body from linolenic acid

eicosanoids

derivatives of 20-carbon fatty acids; biologically active compounds that help regulate blood pressure, blood clotting, and other body functions

lipoprotein lipase (LPL)

an enzyme that hydrolyzes triglycerides passing by in the bloodstream and directs their parts into the cells, where they can be metabolized for energy or reassembled for storage

hormone-sensitive lipase

an enzyme inside adipose cells that responds to the body’s need for fuel by hydrolyzing triglycerides so that their parts enter the general circulation and thus become available to other cells for fuel

solid fats

fats that are not usually liquid at room temperature; commonly found in most foods derived form animals and in vegetable oils that have been hydrogenated

blood lipid profile

results of blood tests that reveal a person’s total cholesterol, triglycerides, and various lipoproteins

cardiovascular disease (CVD)

diseases of the heart and blood vessels throughout the body. atherosclerosis is the main cause of CVD. when the arteries that carry blood to the heart muscle become blocked, the heart sugars damage known as coronary heart disease (CHD)

fat replacers

ingredients that replace some or all of the functions of fat and may or may not provide energy

artificial fats

zero-energy fat replacers that are chemically synthesized to mimic the sensory and cooking qualities of naturally occurring fats but are totally or partially resistant to digestion

olestra

a synthetic fat made from sucrose and fatty acids that provides 0 calories per gram