Carbohydrates

It is a hydrated carbon compounds. It is defined as a poly hydroxyl aldehyde or keton, containing carbon, hydrogen and oxygen, the ratio of hydrogen to oxygen is the same as their ratio in water.
Carbohydrate are divided into:
1- Monosaccharides.
2- Di and oligosaccharides.
3- Polysaccharides.
Monosaccharides
They are the simplest carbohydrates, they consist either of two carbon atoms and called bios, or three carbon atoms (trios), or tetrose (4 carbon), pentose (5 carbon), hexose (6 carbon), heptose(7 carbon), up to nine carbons. Bios are not found freely in the plant.
Disaccharides and oligosaccharides
Disaccharides: are compounds that yield two monosaccharide molecules on hydrolysis.
e.g. sucrose: it yields equimolecular quantities of glucose and fructose. It is the only disaccharide that occurs abundantly in free state in the plant. It is a non-reducing sugar.
Oligosaccharide: (Greek oligo means few), is often applied to saccharides containing 3-10 units of sugar.
Polysaccharides: they are derived from monosaccharides. They are complex, high molecular weight polysaccharides as starch, inulin and cellulose. They can usually be hydrolyzed to the component hexose and therefore are called hexosan.
Carbohydrate utilization:
1- Embden-Meyerhof scheme ( pathway) of glycolysis
2- Tricyclic acid cycle
Complex polysaccharides