The carbohydrate group is divided into five different lists : starch, fruit, milk, sweets, desserts and other carbohydrates and non starchy vegetables :
Mono saccharides include these simple sugars :
The prefix mono means "one" these sugars consist of a single ring of atoms. Mono saccharides are the building blocks of other carbohydrates, such as di saccharides and starch.
Glucose is the most abundant sugar in nature and it is our primary energy source as well. It plays a vital role in proper functioning of the human body. Fructose is the sweetest natural sugar. it is about 1.3 times as sweet as white sugar. Ga lactose is almost always linked to glucose to make milk sugar which is a di saccharides.
This is most commonly occurring carbohydrates containing two or more mono saccharides units linked together. They are also called double sugars which includes
Sucrose is commonly two simple sugar joined together (Glucose and fructose). Sucrose is the chemical name which is called table sugar, white sugar, granulated sugar or simply sugar. Maltose is simply two glucose units connected together. It is fairly abundant in germination of seeds and is produced in the manufacturing of beer. Lactose is called milk sugar which is present in milk and milk products. As per the sweetness is considered lactose is ranked as the lowest sugar. Most carbohydrates are considered as plant products, lactose is one of the few considered exclusively from the animal products.
Raffinose and stachyose are the two most common oligo saccharides, however, as the humans lack the enzyme needed to digest these two carbohydrates, they pass undigested into large intestine, where bacteria break them down.
In the body oligo saccharides are components of cell membranes allowing cells to recognize and interact with one another. Oligo saccharides are also made in the breasts, where they are incorporated into human milk. These compounds are part of a complex system that helps protect the infants from diseases causing pathogens, and they are one of the main reasons for which women are encouraged to breastfeed their infants.
They are made up of many mono saccharides bonded together by glycosidic bonds. The type and the arrangements of sugar molecules determine the shape and form of the poly saccharides. For example, some poly saccharides have an orderly linear appearance, whereas others are shaped like branches on a tree. The three most common poly saccharides are :
Glycogen is a storage form of energy in the animal body, starches play that role in plants and fibers provide structure in stems, trunks, roots, leaves and skins of plants. Both glycogen and starch are built of glucose units, fibers are composed of a variety of mono saccharides and other carbohydrate derivatives.
Starch and sugar are the two carbohydrates which provide most of the energy to our body. During the process of digestion, starch and sugar gets hydrolyzed to glucose. Glucose so produced is absorbed by the blood and transported to various body cells. During respiration most of the glucose is oxidized to produce energy necessary for doing work and carrying out body processes. This can be represented as :
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Cellulose is not digested by our body. So, it acts as a fiber or roughage in our food. It does not provide energy to our body and hence it is not a food.
Sugars are sweet crystalline and soluble in water. These are again classified into two types.
The sugars which cannot further hydrolyzed to simpler sugars. They may classify into two types based on type of carbonyl group.
These yield two to ten monosaccharide molecules on hydrolysis. And, again these are classified into various types based on the number of hydrolyzed products formed.
2. Non sugars
Non sugars are tasteless, amorphous solids and either soluble in water or forms colloidal solutions.
In this synthesis a higher carbohydrate is synthesized from the lower carbohydrate. The lower carbohydrate (Arabinose) is reacted with HCN to form Cyanohydrin
This cyanohydrin on reduction with H2/Pd gives Imines. And these on hydrolysis form higher carbohydrates (Glucose and Mannose).
2. Glucose reacts with hydroxylamine to give monoxime.
HOH2C-(CHOH)4-CHO + HONH2 → HOCH2-(CHOH)4-CH=NOH
Glucose adds a molecule of hydrogen cyamide to give a cyanohydrin.
HOH2C-(CHOH)4-CHO + HONH2 → HOCH2-(CHOH)4-CH=NOH
These reactions confirm the presence of a carbonyl group in glucose.
6. D-glucose reacts with phenyl hydrazine to give glucose phenyl hydrazine which is soluble. If excess od phenyl hydrazine is used, a dihydrazone known as osazone, is obtained.
When treated with concentrated sulfuric acid glucose undergoes dehydration and results in the formation of hydroxy methyl furfural.
The open chain structure of glucose proposed by Bayer explained most of its properties. However, it could not explain the following
When glucose was crystallized from a concentrated solution at 30oC it gave a form of glucose (Melting point 146oC) whose optical rotation is 111o. The b form (Melting point 150o) obtained on crystallization of glucose from a hot saturated aqueous solution at a temperature above 98oC has an optical rotation of 19.2o. These two forms of glucose are called anomers.
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