1. Introduction to CARBOHYDRATE

2. Introduction Carbohydrates are one of the three major
classes of biological molecules.
Carbohydrates are also the most abundant biological molecules in nature.
The general formula for many of the simpler carbohydrates is (CH2O)n, hence the name “hydrate of carbon”
Carbohydrates are carbon compounds that contain large quantities of hydroxyl groups.
Carbohydrates are polyhydroxylated compounds having at least 3 carbon atoms and a potentially active carbonyl group which may be an aldose or a ketose group.

3. functions Variety of important functions in living systems:
nutritional (energy storage, fuels, metabolic intermediates)
components that mediate some forms of intercellular communication
structural (components of nucleotides, plant and bacterial cell walls, arthropod exoskeletons, animal connective tissue)
fibrous cellulose of plants

4. informational (cell surface of eukaryotes -- molecular recognition, cell-cell communication)
osmotic pressure regulation (bacteria)

5. Carbohydrates are chemically characterized as:
Poly hydroxy aldehydes or
Poly hydroxy ketones.

6. Sugars that contain a keto group are called Ketoses. (Carbonyle group)
Sugars that contain an aldehyde group are called Aldoses. (Carbonyle group)
Sugars that contain a keto group are called Ketoses. (Carbonyle group)
Examples of an aldose (A) and a ketose (B) sugar.

7. Isomers
Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. (different structures).
Examples of isomers:
Glucose
Fructose
Galactose
Mannose
Same chemical formula C6 H12 O6

8. EPIMERS
EPIMERS are sugars that differ in configuration at ONLY 1 POSITION.
Examples of epimers :
D-glucose & D-galactose (epimeric at C4)
D-glucose & D-mannose (epimeric at C2)

9. Under normal biological conditions monsaccharides cyclize with only small amounts of the straight chain present in solution. When an aldose cyclizes, the hydroxyl group on the second to last carbon undergoes an intramolecular reaction with the carbonyl group of the aldehyde.
When a ketose cyclizes, the hydroxyl group on the second to last carbon undergoes an intramolecular reaction with the carbonyl group.

10. Six membered ring structures are called Pyranoses .
five membered ring structures are called Furanoses .

11. Classification
Monosaccharides - simple sugars with multiple OH groups. Based on number of carbons (3, 4, 5, 6), a monosaccharide is a triose, tetrose, pentose or hexose.
Disaccharides - 2 monosaccharides covalently linked.
Oligosaccharides - a few monosaccharides (2-10) covalently linked.
Polysaccharides - polymers consisting of chains of monosaccharide or disaccharide units (100 ).

12. Large no. of Glucose
galactose, glucose,
and fructose
2 galactose units, 1 glucose,
and 1 fructos
Glucose & Fructose
Galactose & Glucose
Glucose & Glucose

13. Monosaccharides

14. 1.Triose
Triose are the monosaccharides containing 3 carbon atoms. The molecular formula is C3H6O3.
They are soluble in water
They may contain aldehyde or ketone group.
The triose containing an aldehyde group called aldotriose and containing an ketone group called ketotriose.

15. 2.Tetrose It contains 4 carbon atoms The molecular formula is C4H8O4
Soluble in water
Contain aldehyde or ketone
Tetrose containing aldehyde group called as aldotetrose and containing ketone group called as ketotetrose.
Ketotetrose
Aldotetrose

16. 3. Pentoses The molecular formula is C5H10O5
Soluble in water, it also contains either aldose group or keto group.
The pentose containing an aldehyde group called as aldopentose and containing a keto group is called as ketopentose.
Pentoses are important components of nucleic acids. The biological important of pentoses are ribose (occurs in RNA), deoxyribose (occurs in DNA), arabinose, xylose, and ribulose.

17. 4. hexoses It contains 6 carbon atoms The molecular formula is C6H12O6
Soluble in water
It also contains aldose (Aldohexoses) or ketose (Ketohexoses) group
Common biological important hexoses are glucose, galactose, mannose and fructose.

18. Disaccharides:
Maltose, a cleavage product of starch on hydrolysis (e.g., amylose), is a disaccharide and made up of 2 glucoses α(1→4 linkage).

19. Sucrose, common table sugar, has a glycosidic bond linking the anomeric hydroxyls of glucose & fructose. (1α →2β linkage)
Lactose, milk sugar, is composed of galactose & glucose. (Galactose 1 β →4 glucose linkage)

20. Polysaccharides 2 types:
Homopolysaccharides (all are 1 type of monomer), e.g., glycogen, starch, cellulose
Heteropolysaccharides (different types of monomers), e.g., peptidoglycans, hyaluronic acid.

21. Glucose storage in polymeric form minimizes osmotic effects.
Polysaccharides:
Plants store glucose as amylose or amylopectin, glucose polymers collectively called starch.
Natural starches consist of about 10%–30% amylase and 70%–90% amylopectin. 
Glucose storage in polymeric form minimizes osmotic effects.
Amylose is a glucose polymer.

22. Amylopectin is a glucose polymer with mainly a(14) linkages, but it also has branches formed by a(16) linkages. Branches are generally longer than shown above. Branch points occurring about every 25–30 units
The branches produce a compact structure & provide multiple chain ends at which enzymatic cleavage can occur.

23. Glycogen, the glucose storage polymer in animals, is similar in structure to amylopectin.
But glycogen has more a(16) branches (8–12 glucose units between branches) .
The highly branched structure permits rapid glucose release from glycogen stores, e.g., in muscle during exercise.
The ability to rapidly mobilize glucose is more essential to animals than to plants.

24. Cellulose, a major constituent of plant cell walls, consists of long linear chains of glucose β (1,4)

25. heteropolysaccharides
1. Peptidoglycon:
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria.
 The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid.

26. 2. hyaluronic acid
Hyaluronic acid is a polymer of disaccharides, themselves composed of D-glucuronic acid and D- N-acetylglucosamine, linked via alternating β-1,4 and β-1,3 glycosidic bonds.
Hyaluronic acid distributed widely throughout connective, epithelial, and neural tissues.

27. Functions of carbohydrates
The most important function of carbohydrates is to provide energy to the body. They are also structural components of tissue. Carbohydrates are important in the regulation of fat metabolism.
Structural Components of Cells:
Carbohydrates serve as an important structural material in some animals and plants. E.g glycogen in animal, cellulose in plants.
Major source of energy:
Carbohydrates are essential to life
Almost all animals use them as respiratory fuels.
Breakdown of 1 gram of carbohydrate yields 4 K calories of energy

28. Storage substance of potential energy:
Glucose supplies the immediate energy needed by tissue.
Glucose is the sole form of energy for the brain and other nervous tissue.
Lack of glucose or oxygen for its metabolism leads to rapid damage to brain.
Storage substance of potential energy:
Carbohydrates is stored in the body in the form of glycogen.
The glycogen, stored in liver, controls glucose level in the blood.
Glycogen, stored in muscles, is not available for regulating the blood sugar level.
In plants, starch is the storage substance.

29. Regulation of fat metabolism:
Some carbohydrates are essential for the normal oxidation of fats.
If carbohydrates are restricted in the diet, there is more rapid metabolization of fats. This results in the accumulation of incompletely oxidized intermediate products leading to ketosis.
Protein sparing function:
As long as carbohydrates are present in required amount in the body, it is used as a source of energy. If it is not supplied in required amount, fat and then protein will be utilized as a source of energy.
This is known as protein sparing function.

30. Role in gastro intestinal function:
Lactose promotes the growth of desirable bacteria in the small intestine.
These bacteria synthesize certain B-complex vitamin.
Lactose also increases calcium absorption.
Key role in metabolism:
Carbohydrates play a key role in the metabolism of amino acids and fatty acids.
Cell Recognition:
The gycoproteins, oligosaccharides present in the cell membrane serve as identifiers that assist the cells in their recognition of each other.
Supportive function:
Cellulose in plants and chondroitin sulfate in bone tissue offers supportive function

31. Protective function: Anticoagulants:
High viscosity and mucous – like consistency of acidic heteropolysacchardies account for their role as biological lubricating material for protection of cell surfaces.
They protect the friction surfaces such as blood vessels, urenogenital tracts, digestive tract, mucous membranes of nose, trachea, bronchus, joints etc.. against mechanical damage.
Extracellular gel like mucopolysacchardies impart mechanical strength to the internal organs against compression and vibration
Anticoagulants:
Heparin and sythetic sulfated polysacchardies are widely used as anticoagulants.

32. Osmotic and Ionic regulations:
Biological cement:
Acidic heteropolysachharides such as hyaluronic acid function as intracellular cementing substances.
Osmotic and Ionic regulations:
Hyaluronic acid is an extremely hydrophilic polysaccharide. It controls the extracellular osmotic pressure by binding extracellular water.