Carbohydrates/कार्बोहायड्रेट

Carbohydrates = hydrates of carbon

C_x(H₂O) _y, x=y    ------- C_nH_2nO_n

Carbohydrates are mainly divided in three types –

1.Monosaccharide

2.Oligosaccharide

3.Polysaccharide

1.Monosaccharide – It is smallest carbohydrate molecule. It’s monomer of high carbohydrates. It can’t be hydrolyzed, because it is the smallest unit of carbohydrate. It is soluble in water. It tastes sweet. It’s reducing sugar, because of this character it shows Fehling and Benedict test positive.

Classification –

I. On the basis of number of carbon –

a. Triose – PGAL = Phospho glyceraldehyde, DHAP = Dihydroxyacetone phosphate

b. Tetrose – Erythrose, Erythrulose

c. Pentose – Ribose, Ribulose, Xylose, Xylulose, Deoxyribose

d. Hexose – Glucose, Fructose, Galactose, Mannose

e. Septose/Heptose – Sedoheptulose

II. On the basis of functional group -

a. Aldose (-CHO) – PGAL, Erythrose, Ribose, Xylose, Deoxyribose, Glucose

b. Ketose (>C=O) – DHAP, Erythrulose, Ribulose, Xylulose, Fructose, Sedoheptulose

Glucose also called Dextrose, grape sugar, blood sugar, universal sugar.

Fructose also called Laevulose, fruit sugar, sweetest natural sugar. And galactose called Brain sugar.

2.Oligosaccharide – 2-9 units of monosaccharide forms oligosaccharide. In the middle of two monosaccharide units glycosidic bond is found.

On the basis of monosaccharide units’ oligosaccharide is divided in 4 categories –

I. Disaccharide – it forms when two monosaccharide units bounded by glycosidic bond.

Examples – Maltose = Glucose + Glucose, it is also called malt sugar.

                     Lactose – Glucose + Galactose, it is called milk sugar, because it is present in milk.

                     Sucrose – Glucose + Fructose, it is called cane sugar/table sugar/kitchen sugar/commercial sugar/invert sugar.

Sucrose is an invert sugar because it is a Dextrorotatory molecule and while it is hydrolyzed, the formed solution is levorotatory. It’s a non-reducing sugar. Fehling & Benedict test negative.

II. Tri saccharide – Raffinose – galactose + glucose + fructose

III. Tetra saccharide – Stachyose – galactose + galactose + glucose + fructose

IV. Pent saccharide – Barbacose – galactose + galactose + glucose + glucose + fructose

3. Polysaccharide – It is formed by 10 or more than 10 units of monosaccharide. It is insoluble in water. It doesn’t taste sweet (exception- Inulin). It’s non-reducing sugar. Fehling & Benedict test -negative. It’s mainly divided in two types –

a. Homo-polysaccharide – It is formed by similar monosaccharide units.

Examples – I. Cellulose – it is polymer of β-D-Glucose. It has β-1,4 bond. It is main component of cell wall of plants. It is an organic compound, which found on earth in largest amount.

II. Starch – it is polymer of α-D Glucose; it has two parts – Amylose & Amylopectin. Starch is a type of conserved food in plants.

III. Glycogen – It is polymer of α-D Glucose; it also has two parts – Amylose & Amylopectin. But in comparison of starch it has much Amylopectin, hence Glycogen is more branched molecule. Glycogen is a type of conserved food in animals & fungi.

IV. Chitin – It is polymer of N-Acetyl-D-Glucosamine. It’s a main part of cell wall of fungi, so it is also called fungal cellulose. It forms exoskeleton in insects.

V. Inulin – it is polymer of α-D Fructose. It has α-1,2 bond. Exceptionally it’s soluble & sweet polysaccharide.it is used to found out kidney failure in GFR.

GFR = Glomerular Filtration Rate

It is found in Dahlia plant’s root.

b. Hetero-polysaccharide – It is formed by different monosaccharide units.

Examples – I. Hyaluronic acid – It is found in synovial fluid, which is found in joints. So it is called animal cement.

II. Pectin – It is found in middle lamella of cell wall. It is called plant cement.

III. Hemicellulose – It is a component of cell wall. It is called universal molecule of cell wall.

IV. Chondroitin – It is found in matrix of cartilage.

V. Heparin – It’s a natural Catabolite.