Lecture 4. Classification of CHO &function.pptx

Carbohydrate it's definition, history and classification. Functions.

1. Classification of Carbohydrates

2. Carbohydrates Carbohydrate is an organic compound; it comprises only oxygen, carbon, and hydrogen . The hydrogen: oxygen ratio is usually 2:1. Carbohydrates are hydrates of carbon; technically they are polyhydroxy aldehydes and ketones . Carbohydrates are also known as saccharides, the word saccharide comes from Greek word sakkron which means sugar.

3. Classification Sugars 1. Monosaccharides a) Trioses b) Tetroses c) Pentoses 2. Oligosaccharides a) Disaccharides b) Trisaccharides c) Tetra saccharides Non-Sugar 3 . Polysaccharides a) Homo- glycans b) Hetero- glycans 4 . Complex Carbohydrate a) Glycolipids b) Glycoprotein

4. Monosaccharides Monosaccharides are the simplest form of carbohydrates. They consist of one sugar and are usually colorless, water-soluble, crystalline solids Some  monosaccharides have a sweet taste. Examples of  mono-saccharides  include glucose (dextrose), fructose, galactose, and ribose

5. Stereoisomerism Biologically, D forms are more important

6. Mono- saccrides

7. Glucose Glucose is a  sugar  with the  molecular formula   C 6 H 12 O 6 . It is also known as grape sugar. With 6  carbon  atoms, it is classed as a  hexose , a sub-category of  monosaccharides . α-D-glucose is one of the 16 isomers. The D- isomer  (D-glucose), also known as dextrose, occurs widely in nature, but the L-isomer ( L-glucose ) does not. Glucose is made during  photosynthesis  from water and carbon dioxide, using energy from sunlight. Glucose is stored as a  polymer , in plants as  starch  and in animals as  glycogen , for times when the organism will need it. Glucose circulates in the blood of animals as  blood sugar . Glucose can be obtained by hydrolysis of carbohydrates such as milk, cane sugar, maltose, cellulose, glycogen etc. It is however, manufactured by hydrolysis of cornstarch by steaming and diluting acid.

8. Fructose Fructose, or fruit sugar, is a simple  ketonic   monosaccharide  found in many plants, where it is often bonded to  glucose  to form the disaccharide   sucrose . It is one of the three dietary monosaccharides, along with glucose and  galactose , that are absorbed directly into the bloodstream during  digestion . Pure, dry fructose is a very sweet, white, odorless, crystalline solid and is the most water-soluble of all the sugars. Fructose is found in  honey , tree and vine fruits,   berries , and most root vegetables. Commercially, fructose is frequently derived from sugar cane, sugar beets, and corn. All forms of fructose are commonly added to foods and drinks for  palatability  and  taste  enhancement, and for browning of some foods, such as baked goods. Excessive fructose consumption is believed to be a cause of  insulin resistance ,  leading to  metabolic syndrome ,  type 2 diabetes , and  cardiovascular disease .

9. Galactose Galactose, a  monosaccharide   sugar , less  sweet  than glucose  and  fructose . Galactose when combined with  glucose  (monosaccharide), through a  condensation reaction , results into the  disaccharide ,   lactose . In nature, lactose is found primarily in milk and milk products. Consequently , various food products made with dairy-derived ingredients, e.g. breads and cereals, can contain lactose.  In the human body, glucose is changed into galactose via hexoneogenesis to enable the  mammary glands  to secrete lactose. However , most lactose in milk  is synthesized from galactose taken up from the blood. Glycerol also contributes some to the mammary galactose production.

10. Oligosaccharides Oligosaccharides are compound sugars that yield 2 to 10 molecules of the same or different monosaccharides on hydrolysis.  Oligosaccharides yielding 2 molecules of monosaccharides on hydrolysis is known as a disaccharide , and the ones yielding 3 or 4 monosaccharides are known as trisaccharides and tetrasaccharides respectively and so on. Bacteria in GIT possess enzymes to hydrolyze all oligosaccharides. However, animal cells do not produce the enzymes necessary to hydrolyze In the large intestine, they are degraded by bacterial enzymes to short-chain fatty acids (SCFAs ) that are beneficial for colon health

11. Disaccharide α -1-4 glycocydic linkages

12. Disaccharides It consists of two units of monosaccharides , which link together via glycosidic bond and the elimination of one water molecule Depending upon the monosaccharides present and the manner in which they are linked The most nutritionally important disaccharides are i . Sucrose ii. Maltose iii. Lactose iv. Cellobiose

13. Sucrose The word “ sucrose ” was coined in 1857 by the English chemist William Miller from the French sucre and the generic chemical sufx - ose for sugars in English. α-1,2- glycosidic linkage Sucrose is the most ubiquitous and abundantly occurring disaccharide in plants, where it is the main transport form of carbon Sucrose is very abundant in sugar beets and sugarcane In birds, m olasses inclusion rate is 1-2 % At 160 C, forms barley sugar and at 200 C it forms caramel

14. Lactose β-1,4- linkage Milk Sugar Milk contains 43–48 g/kg lactose It is not as soluble as sucrose and is less sweet, imparting only a faint sweet taste to milk Streptococcus lactis At 150c it turn yellow but at 175c changed into brown compound, lactocaramel Lactose Intolerance

15. Maltose Maltose is a  disaccharide  formed from two units of glucose  joined with an α(1→4)  bond , Maltose is the second member of an important biochemical series of glucose chains. Maltose is the disaccharide produced when  amylase  breaks down  starch . It is found in  germinating  seeds as they break down their starch stores to use for food, which is why it was named after  malt .

16. Cellobiose β-1,4- linkage This linkage cannot be split by mammalian digestive enzymes . It can, however, be split by microbial enzymes It does not exist naturally as a free sugar , but it is the basic repeating unit of cellulose .

17. Polysaccharides Polysaccharides are compound sugars and yield more than 10 molecules of monosaccharides on hydrolysis. They are further classified depending on the type of molecules produced as a result of hydrolysis. They  may be homopolysaccharides i.e , monosaccharides of the same type or heteropolysaccharides i.e., monosaccharides of different types. Example of homopolysaccharides are starch, glycogen, cellulose, pectin (soluble fiber, citrus fruit) Heteropolysaccharides are Hyaluronic acid (skin freshening), Chondrotin (in connective tissue – joints tissue).

18. Starch ( Homoglycan ) Starch  is a  carbohydrate  consisting of a large number of  glucose  units joined by  glycosidic bonds . This   polysaccharide  is produced by most green  plants  as an energy store. It is the most common carbohydrate in human diets and is contained in large amounts in  staple foods  such as  potatoes ,  wheat ,  maize  (corn),  rice , and  cassava . Particularly in grains, seeds (which may contain up to 70% on an as-fed basis), cereal by-products, and tuber It’s generally a mixture of amylose and amylopectin

19. 3 types on basis of digestion a) Rapidly Digested Starch b) Slowly Digested Starch c) Resistant Digested Starch Starch-containing foods must be cooked before they can be more efficiently utilized by chicken and animal The cooking of foods markedly aids in their digestion by animals through breaking down (gelatinizing) and solubilizing starch granules Have highly glycemic Index Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.

20. CARBOHYDRATE

21. CARBOHYDRATE

22. Glycogen( Homoglycan ) Glycogen  is another form of energy storage which is multi branched   polysaccharide  of  glucose  that serves as a form of energy storage in  animals  and  fungi . The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as the secondary long-term energy storage, with the primary energy stores being fats held in  adipose tissue . Muscle glycogen is converted into glucose by muscle cells, and liver glycogen converts to glucose for use throughout the body including the central nervous system.

23. Polysaccharides

24. Cellulose ( Homoglycan ) Cellulose  is, a  polysaccharide  consisting of a linear chain of several hundred to many thousands of  β(1→4) linked   D-glucose  units.  Cellulose is an important structural component of the primary  cell wall  of green plants . Cellulose is the most abundant organic polymer on Earth.  The cellulose content of  cotton  fiber is 90%, that of  wood  is 40–50%. Some animals, particularly  ruminants  and  termites , can  digest  cellulose with the help of  symbiotic  micro-organisms. In humans, cellulose acts as a  hydrophilic  bulking agent for  feces  and is often referred to as a " dietary fiber ".

25. Fiber ( Hetero- glycans ) Non-digestible polysaccharides Does not provide energy to mono gastric animal Soluble ones are i . Gums (Arabinose, galactose, rhamnose and glucuronic acids) ii . Pectin’s (L- rhamnose , D-galactose, L-arabinose and D-xylose) iii . Mucin (Arabinose, galactose, rhamnose and glucuronic acids)

26. Pectin (Soluble) Pectin is a structural  hetero-polysaccharide  contained in the primary  cell walls  of  terrestrial plants .   It is produced commercially as a white to light brown powder, mainly extracted from  citrus fruits , and is used in food as a  gelling agent , particularly in  jams  and jellies. Pectin is a soluble  dietary fiber . In the large intestine and colon, microorganisms degrade pectin and liberate short-chain fatty acids that have positive influence on health.

27. In Soluble Hemicelluloses are defined as alkali-soluble cell wall polysaccharides that are closely associated with cellulose Mainly composed of D-glucose , D-galactose , D-mannose , D-xylose and L-arabinose units joined together in different combinations and by various glycosidic linkages Hemi-cellulose (Insoluble)

28. Lignin (Insoluble) Lignin, which is not a carbohydrate but is closely associated with this group of compounds, confers chemical and biological resistance to the cell wall, and mechanical strength to the plant Highly resistance to chemical degradation

29. Source of energy The main function of carbohydrate is to supply energy for the body processes . A greater part of the energy in the diet (more than 50- 80 %) is supplied by carbohydrates. Some of the carbohydrates are immediately utilized by the tissues and the remaining is stored as glycogen in the liver and muscles and some are stored as adipose tissues for future energy needs. 5 Most Essential Functions

30. Protein-sparing Carbohydrates are mainly utilized by the body of fulfilling the major part of the energy needs, thus sparing protein for tissue building and repairing. The first physiological demand of the body is the need for energy, which must be satisfied before the nutrients are used for other functions. So , this function of carbohydrates to spare protein for its primary purpose of body building and repair of tissues is an important one.

31. Fat Oxidation Fat burns in the fire of carbohydrates‘ so in absence of carbohydrates , fats cannot be oxidised by the body to yield energy. Recent studies show that oxaloacetic acid, a breakdown product of CHOs is essential for the oxidation of acetate, which is the breakdown product of fats. I n the absence of oxaloacetic acid, acetate converted into ketone bodies, get accumulated in the body and the animal suffers from 'Ketosis'- a toxic condition of the body. Ketosis occurs in diabetes, where the cells cannot utilize carbohydrates and in starvation, where the cells must use fat stores in the body as a source of energy.

32. Gastro-intestinal function Carbohydrates play an important role in the gastro-intestinal functions of mammals. Lactose promotes the growth of certain desirable bacteria in the small intestine which brings about the synthesis of certain B-complex Vitamins. Lactose also enhances the absorption of calcium. Cellulose provides fiber and bulk which helps in the stimulation of the peristaltic movements of the gastroinl tract.

33. Flavor Effect Carbohydrate foods add flavor, variety and the diet. Since they are non-irritant, easily digestible when cooked are consumed and forms the staple food of human beings . Improves taste of animal feed