Definition of Lipids

Definition of Lipids
Lipids have been defined as a heterogeneous group of naturally occurring substances that are insoluble in water but soluble in organic solvent such as ether, chloroform, benzene, and acetone. All lipids contain phosphorus and nitrogen. Most lipids are soft solids or liquids at room temperature and are difficult to crystallize.

The major classes of lipids can be summarized as follows:

Simple Lipids (esters of fatty acids and alcohols)
-Fat and oils (esters of glycerol and fatty acids)
-Waxes (esters of long chain monohydroxy alcohols and fatty acids)

Compound Lipids (simple lipids conjugated with nonlipid molecules)
Phospholipids (esters containing phosphoric acid in place of one mole of fatty acid) -Phosphoglycerides
-Sphingolipids
-Inositol phosphatides
Glycolipids (compounds of carbohydrate fatty acids and sphingosinol)
Lipoproteins (complexes of various lipids and proteins)

Derive Lipids (product of hydrolysis of lipids)
-Fatty acids
-Alcohols
-Hydrocarbons
-Fat-soluble vitamins
Definition of Lipids

How Important of Carbohydrates to Our Body?

How Important of Carbohydrates to Our Body?
The word carbohydrate was originally derived from the fact that the greater part of the compound in this class had the empirical formula Cn(H20)n. The value of n ranged from three to many thousands.

This formula is now considered too restrictive, and more useful definitions might be “polyhydroxy aldehydes or ketones and their derivatives”. This latter definition encompasses deoxy sugars, sugar alcohols, sugar acids, and amino sugars.

Carbohydrates occur in fruits and vegetables as storage reserves in seeds, roots, and tubers; in the sap; and as constituents if the structural tissues. They are also found in milk, blood, and tissues of animals.

Carbohydrates are the most abundant food in the world and the most economical as an energy food source. In the American diet, carbohydrate foods constitute approximately 50% of the daily caloric intake.

However, carbohydrates make up an even greater proportion of the diet of peoples of other countries where cereals are a staple. In addition to their value as an expensive source of energy, carbohydrates are important for several reasons.

The body needs carbohydrates in order to use fat efficiently. Many foreign substances are removed from the body through the intermediate formation of glycosides of glucoronic acid. Diseases such as diabetes develop when the body is unable to utilize sugar properly. Some carbohydrates have an effect on the type of bacteria that will grow in the intestine. In some of the lower animals (crab and lobster), a major constituent of the exoskeleton is a polymer of glucosamine.
How important of Carbohydrates to Our Body?

What is ash content?

What is ash content?
When either organic compounds are decomposed or released at high temperature (500C -600C), the remaining residue is the ash.

This residue consists of oxides and salts containing anions such as phosphates, chlorides, sulfates, and other halides and cations such as sodium, potassium, calcium, magnesium, iron, and manganese.

During the ashing process organic salts decompose, losing the carbon-containing moiety. The metal from such salts forms and oxide or reacts with other anions of the matrix. Some metals (e.g., cadmium and lead) may be volatized during ashing; therefore, if the ash is to be examined for trace elements, care should be exercised to prevent losses during ashing.

For most foods, ashing at 485C or less for 12hrwill give acceptable results for trace elements analysis. Losses of minerals due to carbon release can be appreciable from carbon-containing samples.

This mechanical loss of cash can be avoided by starting the incineration in the muffle furnace at a low temperature (room temperature) and allowing the temperature to rise slowly.

Air currents may be a problem if the door of the furnace is opened suddenly. Generally, samples should not be placed ion areas of the furnace closer than 1 in. from the rear wall and 1.5 in form the front.
What is ash content?