LIPIDS Flashcards
(45 cards)
These diverse compounds that make up
the lipid family are so grouped because
they are
insoluble in water
They are also ____ in other organic
solvents such as ether, acetone, and other
lipids.
soluble
serve a variety of important
functions in living organisms.
* They act as chemical messengers, serve as
valuable energy sources, provide
insulation, and are the main components
of membranes.
lipids
Major lipid groups
include
fats
, phospholipids
, steroids,
and waxes
The chemical term includes fats, oils,
and related compounds that are insoluble in
water and greasy to the touch.
* Some food lipids—butter, margarine, or
cooking oil—are easily recognized as fats.
* Other foods that appear to be
carbohydrates, such as bakery items or
potato chips, often contain significant
amounts of fat.
lipid
Lipids are ____compounds
consisting of a carbon chain with
hydrogen and oxygen atoms attached.
Particular lipids may have other
radicals or groups of elements
attached.
* Fatty acids and their related
compounds are the lipids important in
human nutrition.
organic
Lipids have something in common with
carbohydrates: the same chemical elements that
make up carbohydrates
the same chemical elements that make up
carbohydrates—
carbohydrates—carbon, hydrogen, and oxygen—also
make up fatty acids. However, carbohydrates and
lipids have two important structural differences:
Lipids are more ____, with more carbon (C)
and hydrogen (H) atoms and fewer oxygen (O)
atoms.
complex
The common structural units of lipids are fatty
acids, whereas the common structural units of
carbohydrates are .
simple sugars
The saturation or unsaturation of a lipid governs its physical characteristics:
- Saturated fats are hard
- Less-saturated fats are soft
- Unsaturated fats are liquid at room temperature
Lipids composed mostly of saturated fatty acids are called saturated fats.
Although saturated fatty acids are usually found in animal foods, the most saturated
food fats are two oils from plants: (1) coconut oil, which is 88% saturated, and (2)
palm kernel oil, which is 80% saturated. All other saturated fats are of animal origin
as found in meat; butter; whole, reduced-fat, and low-fat milk; and other dairy
products.
Saturated
Food lipids that have a high proportion of fatty acids with a pair of
hydrogen atoms missing, creating one double bond, are called monounsaturated fats.
These lipids are generally from plant sources. Canola oil (isolated from rapeseed) and
olive oil are primarily mono- unsaturated fats.
monosaturated
When fatty acids have four or more spaces unfilled with
hydrogen atoms, creating two or more double bonds, they are
polyunsaturated fats. Many of these fats are from plant sources and include
commonly used cooking oils such as corn oil and safflower oil.
Polyunsaturated fatty acids with two or more double bonds are also classified
according to the position in the carbon chain where the first double bond
appears. These are referred to as essential fatty acids because the body cannot
synthesize an n-3 or n-6 fatty acid. The n-3 fatty acids found in fatty fish have a
role in cardiovascular health.
Polyunsaturated:
Two different fatty acids—linoleic acid (an n-6 fatty
acid) and α-linolenic acid (an n-3 fatty acid) are
essential fatty acids for humans. Arachidonic acid,
another fatty acid important in human nutrition, can be
made from linoleic acid. Two n-3 fatty acids associated
with cardiovascular health—(1) eicosapentanoic acid
(EPA) and (2) docosahexaenoic acid (DHA)—can be
made from α-linolenic acid but these conversion rates
are extremely slow,13,14 and influenced by age, sex,
genetics, and overall dietary intake. Therefore,
individuals need to obtain these acids from regular
servings of fish.
Essential Fatty Acids
The essential fatty acids strengthen cell membranes and prevent a harmful
increase in skin permeability. Essential fatty acid deficiency causes breakdown in skin tissue,
with characteristic eczema and skin lesions. Essential fatty acid deficiency seldom occurs
with the exception of a patient receiving a parenteral nutrition formula that does not
include the essential fatty acids.
Skin integrity:
Polyunsaturated fatty acids can reduce blood lipid levels,
particularly if they are replacing saturated fat in the diet.
Regulation of lipid metabolism:
Normal growth requires an adequate supply of the essential fatty acids, and growth
is impaired in essential fatty acid deficiency; α-linolenic acid is especially important for the
development of brain tissue before and after birth.
Growth
The essential fatty acids regulate the production of enzymes needed for
synthesis of nonessential fatty acids.
Gene expression
Persons with essential fatty acid deficiency have an increased rate of
infection.
Immune Function
EPA and DHA prevent unwanted aggregation of blood platelets
that blocks the flow of blood in major arteries, causing heart attack or stroke.
Aggregation of blood platelets:
Essential fatty acids are metabolic precursors of a group of
physiologically and pharmacologically active compounds known as eicosanoids
- Synthesis of hormonelike agents:
Arachidonic acid and DHA play a critical role in
the brain and neural development of infants;
both are found in breast milk in liberal
amounts. Commercial infant formula sold in the
United States is fortified with arachidonic acid
and DHA to the levels found in human milk.
Based on the important role of DHA in both
prenatal and postnatal development, some
nutrition experts have proposed that both
pregnant and lactating women of DHA from
fish or supplements during pregnancy, the DHA
content of breast milk, and infant health
outcomes such as visual acuity and cognitive
development.
Special Needs of Infants
The best sources of the two essential fatty acids
are vegetable oils. Corn oil, safflower oil, soybean
oil, cottonseed oil, sun- flower oil, and peanut oil
are rich in linoleic acid (an n-6 acid), and α-
linolenic acid (an n-3 acid) is found in flaxseed,
soybean oil, and rapeseed oil (canola oil).
Food Sources of Essential Fatty Acids
