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Chapter 5: Lipids

Triglycerides, Phospholipids, and Sterols
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Approximately what percentage of the lipids in foods are triglycerides?
95
In which forms are most dietary lipids found?
Triglycerides
What percentage of stored body fat is in the form of triglycerides?
99
Lipids that are solid at room temperate are known as....
fats
Lipids that are liquid at room temperature are known as...
oils
What is the chemical composition of fats?
fatty acids and glycerol
A compound composed of carbon, hydrogen, and oxygen with 3 fatty acids attached to a molecule of glycerol would be known as a
triglyceride
What compound is composed of 3 fatty acids and glycerol
Triglyceride
How many double bonds are present in stearic acid
0
What is a property of dietary lipids?
Omega-3 fatty acids are always insaturated
What is the simplest 18-carbon fatty acid?
Stearic acid
What represents a chief source of short-chain and medium-chain fatty acids?
Dairy
How many hydrogen atoms are attached to each carbon adjacent to a double bond?
1
What is the simplest fatty acid found in the diet?
Acetic Acid
Lipids differ in their degree of saturation or unsaturation due to their number of...
double bonds
What is common dietary saturated fatty acid?
stearic acid
Approximately how many carbons are contained in a medium-chain fatty acid?
6-10
What is a common source of medium-chain fatty acids?
Dairy products
What describes a fatty-acid that has one double bond?
monounsaturated
What type of fatty acid is found in high amounts of olive oil?
monounsaturated
What compound is missing 4 or more hydrogen atoms?
polyunsaturated fatty acid
What is a polyunsaturated fatty acid in foods?
linoleic acid
A person wishing to increase consumption of polyunsaturated fats should choose
vegetable oils
An omega-3 fatty acid has its first double bond on the....
third carbon from the methyl end
What is a triacylglyceride?
a triglyceride
The easiest way to increase intake of oleic acid is to consume more
olive oil
A triglyceride always contains 3
fatty acids
What is a feature of polyunsaturated fats?
low melting point
What is known as a tropical oil?
cocoa butter
What is a factor that determines the hardness of a fat at a given temperature?
Degree of saturation
What source would yield the softest lipids at room temperature?
safflower
A major cause of rancidity of lipids in food is exposure to...
heat and oxygen
What structural feature of fatty acids determines their susceptibility to spoilage by oxygen?
Number of double bonds
What is a characteristic of lipids
corn oil and sunflower are more prone to spoilage than palm kernel oil
When stored at room temperature in loosely capped containers, which of the following dietary lipids would turn rancid in the shortest time?
soybean oil
What would be least effective at preventing oxidation of the polyunsaturated fatty acids in processed foods?
addition of phosphorus
What is NOT used by food processors to stabilize the lipids in food products
addition of oxidizing chemicals
What is NOT a characteristic of hydrogenated oils including...
products containing them become rancid sooner, contributing to a shorter shelf life
What has the highest percentage of its fat in a saturated form?
coconut oil
What has the highest percentage of its fat in polyunsaturated form?
corn oil
What characteristics is shared by olive oil and canola oil?
both contain high levels of monounsaturated fatty acids
What provides abundant amounts of omega-3 fatty acids?
flaxseed oil
The food industry often carries out the process of hydrogenation on which lipids?
corn oil
What is considered a major source f polyunsaturated fat?
corn oil
What lipid contain(s) saturated fat?
Butter, cottonseed oil, and soybean oil
what is NOT a rich source of polyunsaturated fatty acids
palm oil
In the process of fat hydrogenation, hydrogen atoms are added to which part of the molecule?
carbon
What is a conjugated linoleic acid?
A fatty acid with the chemical make-up of linoleic acid but with a different configuration
Oil that is partially hydrogenated sometimes changes one or more of its double bond configurations from
cis to trans
What is descriptive of fatty acid configuration?
Naturally occurring trans-fatty acids are found in dairy products
What describes a feature of cis-fatty acids and trans-fatty acids?
In the body, trans-fatty acids are metabolized more like saturated fats than like unsaturated fats
What is a feature of phospholipids?
soluble in both water and fat
The composition of lecithin could include all but
magnesium
What type of compound is lecithin?
phosopholipid
What is the usual fate of dietary lecithin?
hydrolyzed by the intestinal enzyme lecithinase
What is a feature of choline?
is it a part of lecithin
A characteristic of lecithin supplements is they
are mostly hydrolyzed in the intestine
what is NOT a feature of lecithin?
dietary supplements inhibit fat absorption
How much energy is contributed by one gram of lecithin in a dietary supplement?
9 kcal
What is the approximate energy value of one teaspoon of liquid lecithin supplement?
45 kcal
Which characteristics are shared by cholesterol and lecithin?
Both are synthesized in the body
what does not act as an emulsifier in the intestinal tract?
pancreatic lipase
What is the major sterol in the diet?
cholesterol
about how much cholesterol is synthesized by the liver every day
less than 300 mg
What food contains cholesterol?
Roasted turkey
What is the major source of "good" cholesterol?
Endogenous synthesis
A common feature of the plant sterols is they
inhibit absorption of dietary cholesterol
what cannot be found in plants?
Cholesterol
What is a feature of cholesterol?
synthesized by the body
What is another feature of cholesterol?
only about 10% of the body's total cholesterol is extracellular
What is a characteristic of cholesterol?
It is a precursor for bile and vitamin D synthesis
What is another feature of cholesterol?
its daily value is 300 mg
What compound cannot be synthesized from cholesterol?
glucose
What is NOT a destination for cholesterol?
Accumulates on walls of veins
What term may be used to describe a substance that is hydrophobic?
Lipophilic
What is a characteristic of the lipase enzymes?
Salivary gland lipase (lingual lipase) plays an active role in fat digestion in infants
What is not a feature of the bile acids?
Manufactured by the gallbladder
In the digestion of fats, emulsifiers function as
detergents
What part of the gastrointestinal tract is the predominant site of dietary fat hydrolysis?
small intestine
Chylomicrons are synthesized within the
intestinal walls
How is soluble fiber in the diet thought to help lower blood cholesterol level?
It enhances excretion of bile leading to increased cholesterol turnover
Bile is known to assist in the absorption of
fat only
What is the storage site of bile?
gallbladder
Spherical complexes of emulsified fats are known as
micelles
What substance cannot be absorbed directly into the blood?
Long-chain fatty acids
After a meal, most of the fat that eventually empties into the blood is in the form of particles known as
chylomicrons
Your aunt Gladys has a family history of heart disease. She decides to begin eating a bowl of oatmeal every morning to help lower her blood cholesterol. After about a month of following this routine, her cholesterol declined about 5 points. Which of the following is the most likely explanation for this effect?
Oatmeal is high in soluble fibers that trap bile, causing the body to use more cholesterol for bile replacement
What is an example of enterohepatic circulation?
Recycling of bile from the intestine to the liver
What lipoprotein is largest in size?
Chylomicron
In comparison to a low-density lipoprotein, a high-density lipoprotein contains
less lipid.
What lipoproteins contains the highest percentage of cholesterol?
Low-density lipoprotein
What would be the least effective method to control blood cholesterol levels?
eat more insoluble fiber