2.A LIPIDS AND RELATE SYSTEM ( ENERGY-STORAGE LIPIDS: TRIACYLGLYCEROLS)

human cells

With the notable exception of nerve cells, _store small amounts of energy-providing materials for use when energy demand is high.

carbohydrate glycogen

The most widespread energy-storage material within cells is the _; it is present in small amounts in most cells.

triacylglycerols

lipids that also function within the body as energy-storage materials.

Triacylglycerols

are concentrated primarily in special cells (adipocytes) that are nearly filled with the material.

-under the skin

– in the abdominal cavity

– in the mammary glands, and

– around various organs

Adipose tissue containing these cells is found in various parts of the body

Triacylglycerols

are much more efficient at storing energy than is glycogen because large quantities of them can be packed into a very small volume

Triacylglycerols

These energy storage lipids are the most abundant type of lipid present in the human body.

triesters

-three ester functional groups are present

In terms of functional groups present, Triacylglycerols are

alcohol with a carboxylic acid

Recall that an ester is a compound produced from the reaction of an

glycerol, a three-carbon alcohol with three hydroxyl groups

The alcohol involved in triacylglycerol formation is always

carboxylic acids

Fatty acids are the _ involved in triacylglycerol formation.

esterification reaction

In the _ producing a triacylglycerol

– a single molecule of glycerol reacts with three fatty acid molecules; each of the three hydroxyl groups present is esterified

glycerol

has three fatty acids

trimester of glycerol

has three water molecules

ester linkage

Each of the fatty acids is attached to glycerol through an

triacylglycerol

is a lipid formed by esterification of three fatty acids to a glycerol molecule.

acyl group

is the portion of a carboxylic acid that remains after the –OH group is removed from the carboxyl carbon atom

acyl group

triacylglycerol

molecules contain three fatty acid residues (three acyl groups) attached to a glycerol residue.

triglyceride

An older name that is still frequently used for a triacylglycerol is

simple triacylglycerol

is a triester formed from the esterification of glycerol with three identical fatty acid molecules

mixed triacylglycerol

If the reacting fatty acid molecules are not all identical, then the result is a

mixed triacylglycerol

is a triester formed from the esterification of glycerol with more than one kind of fatty acid molecule.

Fats

are naturally occurring mixtures of triacylglycerol molecules in which many different kinds of triacylglycerol molecules are present

Physical state at room temperature

WHAT DISTINGUISHES A FAT FROM AN OIL?

Fat

is a triacylglycerol mixture that is a solid or a semi- solid at room temperature (25°C)

Fat

Generally obtained from animal sources

Oil

is a triacylglycerol mixture that is a liquid at room temperature (25°C).

Oil

Generally obtained from plant sources

Pork fat and Palm Oil

Examples of fat and oil

Fats

are composed largely of triacylglycerols in which saturated fatty acids predominate, although some unsaturated fatty acids are present.

Fats

Such triacylglycerols can pack closely together because of the “linearity” of their fatty acid chains , thus causing the higher melting points associated with fats.

Oils

contain triacylglycerols with larger amounts of mono- and polyunsaturated fatty acids than those in fats

Oils

Such triacylglycerols cannot pack as tightly together because of “bends” in their fatty acid chains. The result is lower melting points.

animal fat

Fats are generally obtained from animals; hence the term _. Although fats are solids at room temperature, the warmer body temperature of the living animal keeps the fat somewhat liquid (semi-solid) and thus allows for movement.

fish oils

Oil typically come from plants, although there are also _ . A fish would have some serious problems if its triacylglycerols “solidified” when it encountered cold water.

Pure fats and pure oils

are colorless, odorless, and tasteless. The tastes, odors, and colors associated with dietary plant oils are caused by small amounts of other naturally occurring substances present in the plant that have been carried along during processing. The presence of these “other” compounds is usually considered

desirabl

oils than with fats

a higher degree of fatty acid unsaturation is associated with

coconut oil

A notable exception to this generalization is _ which is highly saturated.

Coconut oil

This oil is a liquid not because it contains many double bonds within the fatty acids but because it is rich in shorter-chain fatty acids, particularly lauric acid (12:0).

lauric acid (12:0)

Coconut oil is a liquid not because it contains many double bonds within the fatty acids but because it is rich in shorter-chain fatty acids, particularly

DIETARY CONSIDERATIONS AND TRIACYLGLYCEROLS

Numerous studies have shown that, in general, nations whose citizens have high dietary intakes of triacylglycerols (fats and oils) tend to have higher incidences of heart disease and certain types of cancers.

DIETARY CONSIDERATIONS AND TRIACYLGLYCEROLS

Contrary to the general trend, however, there are several areas of the world where high dietary fat intake does not translate into high risks for cardiovascular disease, obesity, and certain types of cancers.

Mediterranean countries and the Inuit people of Greenland

These exceptions, which include some _, suggest that relationships between dietary triacylglycerol intake and risk factors for disease involve more than simply the total amount of triacylglycerols consumed.

triacylglycerol

In dietary discussions, the term fat is used as a substitute for the term_ . Thus a dietary fat can be either a “fat” or an “oil.”

type of dietary fat consumed and the amount of dietary fat consumed

Ongoing studies indicate that both the _ are important factors in determining human body responses to dietary fat

30% of total calories

Current dietary fat recommendations are that people limit their total fat intake to

Saturated fats - <10%

Polyunsaturated fat - 10%

Monounsaturated fat- 15%

Limit of total fat intake

saturated fats

bad fat

monounsaturated fats

good fat

polyunsaturated fats

both good fat and bad fat

Saturated fat

can increase heart disease risk

Monounsaturated fat

can decrease both heart disease and breast cancer risk

Polyunsaturated fat

can reduce heart disease risk but promote the risk of certain types of cancers

olive, avocado, and canola oils

Dietary fats high in “good” monounsaturated fatty acids include

Monounsaturated fatty acids

help reduce the stickiness of blood platelets

helps prevent the formation of blood clots and may also dissolve clots once they form.

tree nuts and peanuts

Many people do not realize that most_ are good sources of MUFAs.

Avocado oil

salad dressings

Rice bran oil

deep fat frying

Olive oil

sautéing

1980’s

In the _, researchers found that the Inuit people of Greenland exhibit a low incidence of heart disease despite having a diet very high in fat.

high-fat diet and a high incidence of heart disease.

This contrasts markedly with studies on the U.S. population, which show a correlation between a

The Inuit diet is high in omega-3 fatty acids (from fish).

The U.S. diet is high in omega-6 fatty acids (from plant oils).

What account for the difference between the two peoples?

Inuit diet

is high in omega-3 fatty acids (from fish).

U.S. diet

is high in omega-6 fatty acids (from plant oils).

double the amount of omega-6 fatty acids and half the amount of omega-3 fatty acids

An American consumes about _ that an Inuit consumes.

fish

Several large studies now confirm that benefits can be derived from eating several servings of _ each week.

omega-3 fatty acid

• The choice of fish is important, however.

• Not all fish are equal in _content.

albacore tuna, salmon, and mackerel

Fatty fish include

Leaner

warm-water fish, which include cod, catfish, halibut, sole, and snapper, do not appear to offer as great a positive effect on heart health as do their “fatter” counterparts.

omega-3 fish oil supplements

Recommendations that the U.S. population increase their consumption of cold-water fish has sparked a demand for

Wild salmon

populations are the primary source for such oil

“fish oil without any fish.”

Research is well advanced in getting

algae

Fish do not make the omega-3 fatty acids they have within themselves. Rather, they obtain these fatty acids from the _ that they feed on.

Genetic engineering experimentsGenetic engineering experiments

are underway in which the genes that allow algae to synthesize omega-3 fatty acids are incorporated into plants.

land-based plants

In the future, _ may become sources for omega-3 fatty acids.

essential fatty acid

is a fatty acid needed in the human body that must be obtained from dietary sources because it cannot be synthesized within the body, in adequate amounts, from other substances.

linoleic acid and linolenic acid

There are two essential fatty acids

Linoleic acid (18:2)

is the primary member of the omega-6 acid family

1. are needed for proper membrane structure

2. serve as starting materials for the production of several nutritionally important longer chain omega-6 and omega-3 acids

IMPORTANCE OF ESSENTIAL FATTY ACIDS

• These essential fatty acids:

Essential fatty acid (linoleic, linolenic)

When these two acids are missing from the diet, the skin reddens and becomes irritated, infections and dehydration are likely to occur, and the liver may develop abnormalities.

Essential fatty acids

If the fatty acids are restored, then the conditions reverse themselves.

• Infants are especially in need of these acids for their growth.

Human breast milk

has a much higher percentage of the essential fatty acids than cow’s milk.

Linoleic acid

is the starting material for the biosynthesis of arachidonic acid.

Arachidonic acid

is the major starting material for eicosanoids substances.

eicosanoids substances.

help regulate blood pressure, clotting, and several other important body functions.

Eicosanoids

are produced from arachidonic acid, a 20- carbon polyunsaturated fatty acid (5,8,11,14- eicosatetraenoic acid)

autacoids

The eicosanoids are considered

Eicosanoids (autacoids)

• They act on cells close to their site of production

• They are rapidly degraded

Eicosanoids

• They have both intercellular signaling, & intracellular signal cascades

Selective COX-2 Inhibitors

• Celecoxib

• Rofecoxib

Non-Selective COX 1&2 Inhibitors

• Aspirin

• Acetaminophen

• Ibuprofen

• Naproxen

• Nabumetone

• Diclofenac

Glucocorticoids (Corticosteroids)

• Beclomethasone

• Dexamethasone

Leukotriene Inhibitors

• Montelukast

• Zafirlukast

• Zileuton

Linolenic acid

is the starting material for the biosynthesis of two additional omega-3 fatty acids.

Eicosapentaenoic acid (20:5, n-3; EPA)

Docosahexanoic acid (22:6, n-3 DHA)

two additional omega-3 fatty acids

EPA (eicosapentaenoic acid)

DHA (docosahexaenoic acid)

are important constituents of the communication membranes of the brain and are necessary for normal brain development.

EPA and DHA

are also active in the retina of the eye

Mood

Cognition/ Behavior

Heart health

Inflammation

DHA AND ELA Omega 3’s

Mood

neural phospholipids/ Involved in brain cell signaling for dopamine and serotonin