chapter 5 lipids. why may sugar alcohols be used in products labeled sugar free or no sugar added? ...

Chapter 5Lipids

Why may sugar alcohols be used in products labeled “sugar free” or “no sugar added”? Sugar alcohols provide no kilocalaries incorrect, they

provide differing amounts kcal Sugar alcohols are not derivatives of sugars incorrect,

some are derived from sugar which has undergone chemical processing such as hydrogenation

Sugar alcohols are not monosaccharides or disaccharides. incorrect

Sugar alcohols are not absorbed into the body. correct

Copyright 2010, John Wiley & Sons, Inc.


Lipids

Lipid is the chemical term for fat. Lipids contribute texture, taste, flavor and

aroma to foods. Fats and oils contain 9 calories per gram. The typical American diet contains about

33% of its energy from fat.


Fat Intake Affects Health


Triglycerides

Triglycerides are the major form of lipid in food and in the body.

Triglycerides consist of three fatty acids attached to a glycerol molecule.

If only one fatty acid is attached to the glycerol it is called a monoglyceride.


Triglycerides


Review: Monosaccharide structure


Most fatty acids in food and in the body are bound to a molecule called

cholesterol.

phospholipids.

lecithin. glycerol.


Fatty Acids The carbon chains of fatty acids vary in length from

a few to 20 or more carbons. Short-chain fatty acids range from 4-7 carbons and

remain liquid at room temperature. Coconut oil is a medium chain fatty acid.


Saturated fatty acids contain carbons in a chain that are bound to two hydrogens.

•Most animal fats contain saturated fatty acids.

Unsaturated fatty acids contain some carbons that are not saturated with hydrogens.

•Omega-3 and omega-6 fatty acids are unsaturated fatty acids.


Fatty Acids


Foods consisting mostly of fatty acids with only single bonds tend to be

solid at room temperature.

soluble in water.

liquid at room temperature.

gaseous at room temperature.


The end of a fatty acid chain containing a methyl group is also referred to as the __________ end.

omega alpha delta beta


Omega-3 and Omega-6 Fatty Acids


Trans Fatty Acids

Trans fatty acids can be created by hydrogenation.

Hydrogenation causes some double bonds to become saturated.

Hydrogenated fats can be found in margarines, vegetable shortening and shelf-stable baked goods.

Trans fatty acids have be shown to raise blood cholesterol levels and increase the risk of heart disease.


Fatty Acids in Food


Phospholipids

Phospholipids are lipids attached to a phosphate group.

Phosphoglycerides are the major class of phospholipids.

Phosphoglycerides can act as emulsifiers. Phosphoglycerides form a lipid bilayer in

membranes, helping to regulate what can pass into and out of a cell.


Phospholipids


Phospholipids consists of glycerol with __________ attached.

3 fatty acids

3 amino acids

2 fatty acids, and a phosphate group

cholesterol


Sterols

Sterols are a type of lipid found in plants and animals. Sterols do not dissolve in water. Cholesterol is a type of sterol found only in animals. 90% of cholesterol in the body is found in cell

membranes. Diets high in cholesterol (from animals) can increase

the risk of heart disease. Plant sterols can help reduce cholesterol in the body.


Bile, vitamin D, and some hormones such as testosterone and estrogen are derived from

essential fatty acids.

cholesterol.

trans fatty acids.

phospholipids.


Chylomicrons

Chylomicrons are a combination of triglycerides, cholesterol, phospholipids and a small amount of protein.

Chylomicrons help to transport long-chain fatty acids into the lymphatic system and into the blood stream without passing through the liver.


Chylomicrons


Chylocmicrons are formed in:

the intestine

the liver

the lymph

the blood


Reverse cholesterol transport is accomplished by

a) chylomicrons.

b) LDLs.

c) VLDLs.

d) HDLs.


Lipoproteins

Lipoproteins are transport particles for water-insoluble lipids.

Lipoproteins are created by combining water-insoluble lipids, phospholipids and proteins.

Lipoproteins help transport triglycerides, cholesterol and fat-soluble vitamins from the small intestine and stored lipids from the liver.


Lipoproteins


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Low-Density Lipoproteins

The liver is the major lipid-producing organ in the body.

Triglycerides produced in the liver are incorporated into entities called very-low-density lipoproteins (VLDLs).

VLDLs transport lipids out of the liver and deliver them to cells in the body.

The enzyme lipoprotein lipase removes triglycerides from VLDLs, creating intermediate-density lipoproteins (IDLs).


Low-Density Lipoproteins Approximately two-thirds of IDLs return to the

liver; the remainder are transformed in the blood into low-density lipoproteins (LDLs).

LDLs contain less triglyceride and more cholesterol than VLDLs. LDLs deliver cholesterol to the cells.

If the amount of LDL cholesterol in the blood exceeds the amount that can be used by the cells, the result is a high level of LDLs.

High levels of serum LDLs have been associated with an increased risk for heart disease.


High-Density Lipoproteins

Most cells cannot break down cholesterol. Cholesterol is returned to the liver to be eliminated from

the body. This reverse cholesterol transport is done by high-

density lipoproteins (HDLs). High levels of HDL in the blood help to prevent

cholesterol from depositing in the artery walls. High levels of HDL are associated with a reduction in

heart disease risk.


Lipid Functions in the Body

Most lipids in the body are triglycerides stored in adipose tissue.

Deposits of adipose tissue help to define body shape, provide stored energy, insulate the body from temperature changes and protect internal organs against physical shock.

Lipids in the body are important for lubricating body surfaces, such as the mucous membranes of the eyes.


If you were to analyze the composition of adipose tissue, you would likely find an abundance of

a) micelles.

b) triglycerides.

c) eicosanoids.

d) cholesterol.



Cholesterol is used to make several hormones, including estrogen and testosterone.

PUFAs help to regulate blood pressure and blood clotting.

Essential fatty acids are important for growth, skin integrity, fertility and the structure and function of cell membranes.



Eicosanoids are made from omega-3 and omega-6 fatty acids. Eicosanoids help regulate blood clotting, blood pressure and immune function.

Fatty acids and glycerol can be used to produce energy in the form of ATP.


Lipids Can Be Used to Produce Energy in the Body


Essential Fatty Acid Deficiency If adequate amounts of essential fatty acids

are not consumed, a deficiency can result. Symptoms include: dry, scaly skin, liver

abnormalities, poor wound healing, growth failure in infants and impaired hearing and vision.


Lipids and Cardiovascular Disease Over 80 million Americans suffer from some

form of cardiovascular disease. Studies show that diet and lifestyle affect the

risk of developing cardiovascular disease. Atherosclerosis is a disease in which lipids

and fibrous materials are deposited in artery walls.


Lipids and Cardiovascular Disease


Lipids and Cardiovascular Disease Dietary factors that may help to reduce the

risk of heart disease include: Consuming omega-3 and omega-6

polyunsaturated fats Consuming monounsaturated fats Consuming plant foods, including fruits and

vegetables, whole grains and legumes Adequate intake of B vitamins Moderate alcohol consumption


Recommendations to Reduce Blood Cholesterol


Tools for Assessing Fat Intake


Dietary Fat and Cancer Dietary Fat has been suggested to be both a

tumor promoter and a tumor initiator.


How to Choose Fats Wisely


Reduced-Fat Foods

Reduced-fat foods either have fat removed, have fat replaced or contain fats that cannot be digested or absorbed.

Fat substitutes can be carbohydrate-, protein- or fat-based.

Fat-based fat substitutes, such as Olestra (sucrose polyester), can reduce the absorption of fat-soluble vitamins.


Chapter 5

Copyright 2010 John Wiley & Sons, Inc.All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein.

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