Lipids

LIPIDSClassification, Functions,

and Properties

DEFINITION• Lipids are organic substances made up of

fatty acids and their naturally-existing compounds and derivatives

• In nutrition, lipids provide the much needed CALORIES to “burn” as fuel for ENERGY, secondary to carbohydrates

• Some micronutrients function well only in the presence of fats or lipids

• Lipids yield fatty acids upon hydrolysis• They combine with fatty acids to form

esters• They contain C, H,O,N sometimes K• Relatively INSOLUBLE IN WATER and

ordinary solvents• Soluble in nonpolar/organic solvents like

ether, chloroform, acetone, benzene

CLASSIFICATION OF LIPIDSA. SIMPLE LIPIDS Esters of fatty acids with various

alcohols1. Neutral fats (glycerol esters)2. Waxes (esters of higher alcohols) ex: Cholesterol esters,Vitamin A,D

esters

B. COMPOUND LIPIDS1. Lipids that contain other radicals such as

Phosphoric acids,or a nitrogenous base Ex: lecithin, Cephalin, Lipositol2. Glycolipids- contain Carbohydrate and

Nitrogenous base3. Ill-defined lipids amino lipids(Have NH2) sulfo lipids (have SO4)

C. DERIVED LIPIDS- Lipids that are products of hydrolysis

of simple and compound lipids1. Saturated and Unsaturated Fatty

acids2. Mono and Di glycerides3. Alcohols( sterols and cholesterol)4. Miscellaneous (ex Squalene,

Carotenoids, Vitamins D, E, K)

FATS

• Are esters of fatty acids with GLYCEROL• EXAMPLES:1. Animal fats- Oleic, palmitic, stearic acid2. Mutton fat- more stearic and less oleic than

pork3. Butter fat- mainly palmitic and oleic, with small

amounts of butyric acid and caproic acids4. Human Fat- mostly oleic acid, yellowish tinge is

due to carotene and xanthrophyl pigments

CHEMICAL PROPERTIES

1.Hydrogenation(introduction of highly pressurized Hydrogen)

2. Oxidation( exposure to Oxygen)3. Hydrolysis (breaks down into

simpler forms)4.Saponification ( process of soap

making)

APPLICATION OF ITS CHEMICAL PROPERTIES

A. HYDROGENATION Hydrogenation converts liquid vegetable oils

into solid or semi-solid fats, such as those present in margarine. Changing the degree of saturation of the fat changes some important physical properties such as the melting range, which is why liquid oils become semi-solid.

Other advantages: longer shelf life, oxidative stability, cheaper

B. OXIDATION Oxidative rancidity is associated with

the degradation by oxygen in the air. Via a free radical process, the double bonds of an unsaturated fatty acid can undergo change, releasing volatile aldehydes and ketones. This process can be suppressed by the exclusion of oxygen or by the addition of antioxidants. Oxidation primarily occurs with unsaturated fats.

• When these processes occur in food, undesirable odors and flavors can result. In some cases, however, the flavors can be desirable (as in aged cheeses). In processed meats, these flavors are collectively known as warmed over flavor. Rancidification can also detract from the nutritional value of the food. Some vitamins are highly sensitive to degradation.

3. HYDROLYSIS Hydrolytic Rancidity• Hydrolytic rancidity occurs when water splits fatty

acid chains away from the glycerol backbone in triglycerides (fats). The chemical term is ester hydrolysis. Usually this hydrolysis process goes unnoticed, since most fatty acids are odorless and tasteless. When, however, the triglyceride is derived from short chain fatty acids, the released carboxylic acid can confer strong flavors and odors. A particular problem arises with butter, which contains triglycerides with a high content of butyric acid derivatives.

4.SAPONIFICATION This is a process that produces soap, usually

from fats and lye. In technical terms, saponification involves base (usually caustic soda NaOH) hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes produces glycerol. "Saponifiable substances" are those that can be converted into soap.

Saponification reaction

FATTY ACIDSA. SATURATED fatty acids composed of single bonds

and are usually solid at room temperature

These are fats from animal sources Butter, lard

B .UNSATURATED FATTY ACIDS fatty acids that are composed of one

or more double bonds They are usually liquid at room

temperature “OILS” are mostly from plant sourcesOlive oil, corn oil, linseed oil, palm oil

OTHER IMPORTANT FATTY ACIDS

1. Omega Fatty acids (polyunsaturated) Main source: Fish and Fish oil2. Linoleic,Linolenic, Arachidonic Acid Sources: Nuts, Plant oils ** These are not readily produced by the body,

defficiency may lead to impaired growth and reproduction, eczema,dermatitis,excessive thirst, kidney damage

FUNCTIONS OF FATS IN THE BODY

1.Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats are also sources of essential fatty acids, an important dietary requirement.

2. Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function.

3. Fats also serve as energy stores for the body, containing about 37.8 kilojoules (9 calories) per gram of fat. They are broken down in the body to release glycerol and free fatty acids. The glycerol can be converted to glucose by the liver and thus used as a source of energy.

4. Fat also serves as a useful buffer towards a host of diseases. When a particular substance, whether chemical or biotic—reaches unsafe levels in the bloodstream, the body can effectively dilute—or at least maintain equilibrium of—the offending substances by storing it in new fat tissue. This helps to protect vital organs, until such time as the offending substances can be metabolized and/or removed from the body by such means as excretion, urination, accidental or intentional bloodletting, sebum excretion, and hair growth.

***While it is nearly impossible to remove fat completely from the diet, it would also be unhealthy to do so. Some fatty acids are essential nutrients, meaning that they can't be produced in the body from other compounds and need to be consumed in small amounts. All other fats required by the body are non-essential and can be produced in the body from other compounds

Thank you!