2. lipophobic: Adverse to fat solvents; insoluble fat and fat solvents. 4. squalene: A cholesterol precursor found in whale liver and plants.

Size: px

Start display at page:

Download "2. lipophobic: Adverse to fat solvents; insoluble fat and fat solvents. 4. squalene: A cholesterol precursor found in whale liver and plants."

Winfred Bridges
5 years ago
Views:

1 Chapter 5 Lipids Key Terms 1. hydrophilic: Can mix with or dissolve in water. 2. lipophobic: Adverse to fat solvents; insoluble fat and fat solvents. 3. adipocytes: Fat cells. 4. squalene: A cholesterol precursor found in whale liver and plants. 5. diglyceride: A molecule of glycerol combined with two fatty acids. 6. subcutaneous fat: Fat stores under the skin. 7. cholesterol: A waxy lipid whose chemical structure contains multiple hydrocarbon rings. 8. visceral fat: Fat stores that cushion body organs. 9. chain length: The number of carbons that a fatty acid contains. Foods contain fatty acids with chain lengths of 4 to 24 carbons, and most have an even number of carbons. 10. hydrogenation: A chemical reaction in which hydrogen atoms are added to a fat; it produces more saturated fatty acids and converts some unsaturated fatty acids from a cis form to a trans form. 11. lanugo: Soft, downy hair that covers a normal fetus from the fifth month but is shed almost entirely by the time of birth. It also appears on semistarved individuals who have lost much of their body fat, serving as insulation normally provided by body fat. 12. phytosterols: Sterols found in plants. These are poorly absorbed by humans and reduce intestinal absorption of cholesterol. They recently have been introduced as a cholesterollowering food ingredient.

2 13. conjugated linoleic acid: A polyunsaturated fatty acid in which the position of the double bonds has moved so that a single bond alternates with two double bonds. 14. omega-3 fatty acid: An essential fatty acid; alpha-linolenic acid is the major type. 15. elongation: Addition of carbon atoms to fatty acids so as to lengthen them into new fatty acids. 16. micelles: Tiny emulsified fat packets. They are composed of emulsifier molecules (phospholipids) oriented with their fat-soluble part facing inward and their water-soluble part facing outward toward the surrounding aqueous environment. 17. steatorrhea: Production of stool with an abnormally high amount of fat. 18. adipose tissue: Body fat tissue. 19. eicosanoids: A class of hormonelike substances formed in the body from long-chain essential fatty acids. 20. very-low-density lipoproteins (VLDLs): The triglyceride-rich lipoproteins formed in the liver. They enter the bloodstream and are gradually acted upon by lipoprotein lipase, releasing triglyceride to body cells. 21. omega-6 fatty acid: An essential fatty acid; linoleic acid is the primary type. 22. omega-9 fatty acid: Any polyunsaturated fatty acid in which the first double bond starting from the methyl (CH3) end of the molecule lies between the ninth and tenth carbon atoms. 23. monounsaturated fatty acid: A fatty acid in which the carbon chain contains one double bond. 24. intermediate-density lipoproteins (IDLs): The lipoproteins formed when lipoprotein lipase strips some of the triglycerides from VLDL.

3 25. sterols: A category of lipids that includes cholesterol. They are hydrocarbons with several rings in their structures. 26. oxidation: Oxygen attaches to the double bonds of unsaturated fatty acids. This process causes fats to become rancid. 27. phosphate group: A chemical group that contains phosphate ( PO 4 ) attached to a larger molecule. 28. polyunsaturated fatty acid: A fatty acid in which the carbon chain contains two or more double bonds. Fill-in-the-Blank 1. The major enzyme responsible for the breakdown of lipoproteins and triglycerides in the blood is lipoprotein lipase. 2. Alpha-linoleic acid is an essential omega-3 fatty acid that contains 18 carbon atoms and 3 carbon carbon double bonds (18:3). 3. A trans fatty acid is an unsaturated fatty acid in which the hydrogens surrounding a double bond are on opposite sides of the carbon chain. 4. A cis fatty acid is an unsaturated fatty acid with a bent carbon chain. Most naturally occurring unsaturated fatty acids are these. 5. Glycerol is the backbone of mono-, di-, and triglycerides; alone, it is a thick, smooth liquid. 6. Desaturation is the insertion of double bonds into fatty acids to change them into newer fatty acids. 7. Ester is a chemical combination of an organic acid and an alcohol.

4 8. A triglyceride is an ester of three fatty acids and glycerol. 9. Essential fatty acids (EFAs) are fatty acids that the body needs but cannot synthesize and must obtain from the diet. 10. Olestra is a fat replacer made from a sucrose backbone with six to eight fatty acids attached. The fatty acid arrangement prevents breakdown by the digestive enzyme lipase, so the fatty acids are not absorbed. It can withstand heat and is stable at frying temperatures. Trade name is Olean. 11. Fatty acids are compounds containing a long hydrocarbon chain with a carboxyl group ( COOH) at one end and a methyl group ( CH 3 ) at the other end. 12. A fatty acid in which the carbon chain contains one or more double bonds is an unsaturated fatty acid. 13. Phospholipids are compounds that consist of a glycerol molecule bonded to two fatty acid molecules and a phosphate group with a nitrogen-containing component. They have both water-soluble and fat-soluble regions, which make them good emulsifiers. 14. The blood lipoproteins that contain high levels of protein and low levels of triglycerides are called high-density lipoproteins (HDLs). Synthesized primarily in the liver and small intestine, these lipoproteins pick up cholesterol released from dying cells and other sources and transfer it to other lipoproteins. They are sometimes called good cholesterol. 15. A molecule of glycerol combined with one fatty acid is a monoglyceride. 16. Low-density lipoproteins (LDLs) are the cholesterol-rich lipoproteins that result from the breakdown and removal of triglycerides from IDL. Sometimes called bad cholesterol.

5 17. Very low-density lipoproteins (VLDLs) are triglyceride-rich lipoproteins formed in the liver that, when enter the bloodstream, are gradually acted upon by lipoprotein lipase, releasing triglycerides to body cells. 18. A fatty acid completely filled by hydrogen, with all carbons in the chain linked by single bonds, is a saturated fatty acid. 19. Linoleic acid is an essential omega-6 fatty acid that contains 18 carbon atoms and 2 carbon carbon double bonds (18:2); it is a thin liquid at room temperature. 20. Fat replacers are compounds that imitate the functional and sensory properties of fats, but contain less available energy than fats. 21. Choline is a nitrogen-containing compound that is part of phosphatidylcholine, a phospholipid. It also is part of the neurotransmitter acetylcholine. The body can synthesize it from the amino acid methionine. 22. In the body, lecithin is a phospholipid with the nitrogen-containing component choline. In foods, it is a blend of phospholipids with different nitrogen-containing components. 23. A trans fatty acid is an unsaturated fatty acid with a straighter chain than a cis fatty acid, usually as a result of hydrogenation; it is more solid than a cis fatty acid. 24. A chylomicron is a large lipoprotein formed in intestinal cells following the absorption of dietary fats. It has a central core of triglycerides and cholesterol surrounded by phospholipids and proteins. 25. Nonessential fatty acids are fatty acids that your body can make when they are needed. It is not necessary to consume them in the diet.

6 26. A lipoprotein is a complex that transports lipids in the lymph and blood. It consists of a central core of triglycerides and cholesterol surrounded by a shell composed of proteins, cholesterol, and phospholipids. The various types differ in size, composition, and density. 27. Enterocytes are also referred to as intestinal cells. Fill-in-the-Blank Summaries Fatty Acids Are Key Building Blocks Lipids are a broad range of molecules that dissolve easily in organic solvents, but are much less soluble in water. They are generally hydrophobic (insoluble in water) and lipophilic (attracted to fat and fat solvents; fatsoluble). The three main types of lipids are triglycerides, phospholipids, and sterols. Triglycerides are the largest category of lipids and are stored in the body in adipose tissue. Phospholipids are major building blocks of cell membranes. They keep fats suspended in watery fluids. The most famous sterol, cholesterol, is manufactured in the body and is a precursor to the synthesis of sex hormones, adrenal hormones, and vitamin D. Lipids share many of the same functional properties and transport mechanisms. A triglyceride is made of 3 fatty acids attached to a glycerol molecule. Triglycerides are esters that form when a hydrogen and an oxygen from the carboxyl group combine with a hydrogen atom from the alcohol s hydroxyl group. A molecule of water is produced, which makes this a condensation reaction.

7 Lipids in the Body and the Diet Lipoprotein carriers transport lipids through the bloodstream. Chylomicrons are formed in the intestinal tract. They eventually reach the bloodstream through the jugular veins in the neck. As they travel through the bloodstream, they gradually give up triglycerides to capillary walls. Lipoprotein lipase breaks them down. After 10 hours little is left of the chylomicron except cholesterol-rich remnants. HDLs are scavenger lipoproteins, picking up excess cholesterol released by dying cells and arterial plaques. These plaques are created by LDL degrading over a long period of time. White blood cells that have embedded themselves in arterial walls damaged by smoking or diabetes have scavenger receptors that bind to LDL and cause it to release its cholesterol. If HDL levels are low, there is an increased risk for atherosclerotic heart disease. The Daily Value on food labels recommends consuming 65 grams of fat based on a 2,000 kilocalorie diet. To fulfill the need for omega-6 fatty acids, linoleic acid should provide 2 percent of our calories. When protein is used as part of a fat substitute, the product cannot be used in cooking because high temperatures cause denaturation. Many products use carbohydrates as fat replacements and bind water to further dilute calories. Olestra is a very controversial fat substitute. Because olestra is not absorbed, it may cause symptoms of fat malabsorption such as diarrhea.

8 Short Answer 1. High cholesterol can be a serious threat to health; however, severely low cholesterol can also signal danger in the body. Name three (3) illnesses that may be present along with low cholesterol. Answers may include any of the following: some kinds of stroke; lung, liver, and behavioral illnesses; and reduced immunity (including AIDS). 2. The AHA s guidelines focus on overall eating patterns rather than specific percentages of dietary fat. What are the four main goals of the new guidelines? Answers should include the following: (1) achieve an overall healthy eating pattern; (2) achieve and maintain an appropriate body weight; (3) achieve and maintain a desirable blood cholesterol profile; and (4) achieve and maintain a desirable blood pressure. 3. Explain why fat-free foods are not always lower in calories than regular food. When you take out the fat, sometimes you have to boost the flavor with sugar, sodium, or other additives to have a tasty product. This means that fat-free foods sometimes aren t any lower in calories than regular food. 4. Name two characteristics that distinguish saturated fatty acids from unsaturated fatty acids. Unsaturated fatty acids typically have lower melting points and are more likely to be liquid at room temperature compared to saturated fatty acids. Foods rich in saturated fatty acids tend to be solid at room temperature and have higher melting points than unsaturated fatty acids. 5. Identify the difference between cis- and trans-fatty acids. The configuration around the double bond.

9 6. Describe the role of omega-3 fatty acids in disease prevention. The eicosanoids derived from EPA have the overall effect of dilating blood vessels, discouraging blood clotting, and reducing inflammation. Additional health benefits that have been associated with omega-3 fatty acids include the secondary prevention of chronic diseases and an association with inflammatory conditions, ulcerative colitis, cardiovascular disease, type 2 diabetes mellitus, renal disease, mental function, and growth and development. 7. How much energy from fat will a person receive from eating a serving of potato chips that contains 10 grams of fat? 10 grams of fat 9 Kcalories per gram = 90 Kcalories from fat 8. What percent of energy comes from a serving of potato chips that contains 10 grams of fat and 150 total Kcalories? 10 grams of fat 9 Kcalories per gram = 90 Kcalories from fat 150 total Kcalories = (to convert to a percent) = 60% of Kcalories comes from fat 9. The Daily Value suggests 65 grams of fat as acceptable within a 2,000 Kcalorie diet. If a serving of potato chips contains 10 grams of fat, what percentage of the Daily Value is that? How can you use this Daily Value to determine if you are meeting the estimated needs for fat? 10 grams of fat (from the potato chips) 65 grams of fat for the suggested DV = about 15 percent. By eating a serving of potato chips, you have used 15 percent of your total fat suggested for the day. In choosing what else you will eat today, keep in mind that you have used 10 of the allowed 65 grams, so you have 55 grams, or 85 percent of your daily fat intake left.

10 10. Why do health professionals often recommend eating foods rich in soluble fiber to lower blood cholesterol? When there are plenty of plant sterols and dietary fiber in the intestine, especially fiber from fruits, vegetables, oats, peas, and beans, cholesterol absorption decreases. Soluble fibers bind bile salts and cholesterol and carry them out of the colon. 11. Describe why a high level of HDL has a protective effect against atherosclerotic heart disease. HDL picks up cholesterol released by dying cells and from cell membranes as they are renewed. HDL also picks up cholesterol from arterial plaques, reducing their accumulation. HDL hands off cholesterol to other lipoproteins, especially IDL, which return the cholesterol to the liver for recycling.

History. Aron first proposed that fat may be essential for normal growth Tested on animals-vitamins A,D,E added. Fat deficiency severely affected

History. Aron first proposed that fat may be essential for normal growth Tested on animals-vitamins A,D,E added. Fat deficiency severely affected Chapter 5 LIPIDS History 1918 Aron first proposed that fat may be essential for normal growth Tested on animals-vitamins A,D,E added Fat deficiency severely affected Bone growth Reproduction Called Vitamin