ACTIVITY 9 - QUALITATIVE TEST FOR LIPIDS

Lipids

The _____ are heterogeneous group of naturally occurring substances.

Lipids

They are characterized by their insolubility in water and their solubility in nonpolar solvents such as ether, chloroform, benzene, and hot alcohol.

fat-soluble vitamins and the essential fatty acids

Lipids are important dietary constituents not only because of their high energy value but also because of the _________ and the essential _________ contained in the fat of natural foods.

Fat

In the body, this serves as an efficient source of energy, both directly and potentially, when stored in adipose tissue.

Fat

It serves as a thermal insulator in the subcutaneous tissues and around certain organs.

Nonpolar lipids

These set as electrical insulators allowing rapid propagation of depolarization waves along myelinated nerves.

True

True or False?

The fat content of nerve tissue is particularly high.

lipoproteins

Combinations of fat and proteins, or ________, are important cellular constituents occurring both in the cell membrane and in the mitochondria within the cytoplasm, and serving also as a means of transporting lipids in the blood.

1. Simple lipids

2. Compound lipids

3. Derived lipids

Lipids are classified into what groups depending on their structures?

Simple lipids

These are esters of fatty acids with various alcohol which include triacylglycerols or triglycerides and waxes.

olive oil (plant derived triglyceride) and cod-liver oil (animal derived triglyceride)

What are examples of simple lipids?

Compound lipids

These are esters of fatty acids with alcohol plus other groups (phosphate, carbohydrate, and nitrogenous components).

1. Phospholipids

2. Glycolipids

3. Lipoproteins and Proteolipids

Compound lipids are categorized into three, what are they?

Phospholipids

These are lipids which contain a phosphoric acid residue such as glycerophospholipids

Glycolipids

These are compounds of the fatty acids with carbohydrate, containing nitrogen. These group includes the cerebrosides.

Lipoproteins and proteolipids

These are lipids associated with proteins

Derived lipids

These refer to derivatives obtained by hydrolysis of simple and compound lipids as long as they still possess the general physical characteristics of lipids.

1. Saturated fatty acids

2. Unsaturated fatty acids

3. Mono and diglycerides

4. Steroids

5. Other related compounds such as bile acids and bile salts, carotenoids, tocopherols

Derived lipids are classified into 5, what are they?

Saturated fatty acids

Are those which do not contain multiple bonds in their structures. Examples are Palmitic acid, Stearic acid from cocoa butter, and animal lipid; Lignoceric acid from peanut oil, and Lauric acid from coconut oil.

1. Palmitic acid

2. Stearic acid from cocoa butter, and animal lipid

3. Lignoceric acid from peanut oil

4. Lauric acid from coconut oil

What are examples of saturated fatty acids?

Unsaturated fatty acids

These have structures similar to saturated ones but contain at least one or more double bonds.

1. Oleic acid (olive oil)

2. Linoleic acid (corn and soybean oil)

3. Vegetable oil (rich in unsaturated fatty acids)

What are examples of unsaturated fatty acids?

Mono and diglycerides

Are obtained from incomplete esterification of glycerol by various fatty acids.

Steroids

Are compounds which contain the cyclopentanoperhydrophenanthrene nucleus.

Cholesterol

The most important member of the group in steroids is _______, which occurs in animal fats. 

Atherosclerosis

Steroids are present in blood and its abnormal level is related to what?

Other-related compounds

Bile acids and bile salts, carotenoids, (B-carotene, a precursor of vit. A), tocopherols (vit E group)

True

True or False?

The analysis of lipids includes detection of certain characteristic groups using different chemical reactions.

Baeyer test

It is a test for unsaturated compounds (such as unsaturated fatty acids) in which potassium permanganate is used. In this test the pink color of potassium permanganate disappears when an alkaline potassium permanganate is added to a compound with an unsaturated hydrocarbon. The disappearance of pink color may take place with or without the formation of brown precipitate of manganese oxide.

Acrolein test

The presence of Glycerol grouping as in coconut oil can be detected by means of the _____ test. In this test, the Glycerol group is oxidized (brought about by heating with a dehydrating agent, KHSO₄). The unsaturated aldehyde, Acrolein, is formed which has a characteristic acid, irritating odor. The reaction is shown below:

Acrolein test

Fats and oils are usually differentiated from waxes by means of this test because waxes do not contain the glycerol grouping.

Lieberman-Burchard reaction, Salkowski reaction

Cholesterol produces distinctive colored condensation products when combined with acetic anhydride and concentrated sulfuric acid in the _______ reaction or with chloroform in sulfuric acid in the _______ reaction. 

A basis for a lot of quantitative cholesterol determinations.

Deep blue-green

A positive result in Lieberman-Burchard reaction produces a solution that is _____ color.

Red

A positive result in Salkowski reaction produces a solution that is _____ color.

Carr-Price reaction

Vitamin A is detected by what reaction? This reaction involves a series of color changes until finally a pink solution is obtained.

Furter-Meyer test

The modified ___________ test is used to determine tocopherols (vitamin E) in foodstuffs.

bronze-red

The ______ color which develops is specific for tocopherols.

yellow or brown

Carotenoids and certain sterols produce a _____ or _____ color when present in sufficient quantity may mask the bronze-red color of small amounts of tocopherols.