Digestion and absorption of lipids ppt

Digestion and absorption of lipids ppt
what is lipid ppt
digestion of lipid ppt
phase of digestion and absorption ppt
phases of lipids ppt
digestion in mouth and stomach ppt
digestion in small intestine ppt
secretion of lipids ppt
enzyme involved in lipid digestion ppt
transportation phases of lipids ppt
principles of lipid digestion ppt

1. DIGESTION AND ABSORPTION OF LIPIDs

2. Organic substances relatively insoluble in water, soluble in organic solvents ( alcohol, ether etc), actually or potentially related to fatty acids and utilized by the living cells They are not polymer unlike proteins and nucleic acid They are mostly small molecules A class of compounds distinguished by their insolubility in water and solubility in non-polar solvent. WHAT IS LIPID?

3. Triglyceride is the simplest lipid. consist of one glycerol and three fatty acid. H 2 C------OH HC-------OH + 3 R----COOH H 2 C------OH

4. A short view of lipids in biological system is that, they help in; Providing mechanical barrier by formation of cell membrane. Several essential vitamins are lipids. Provide energy for life. Also form essential hormone like testosterone, steroid, etc. Building block IMPORTANCE:

5. Like carbohydrate and protein lipids are also broken into small component for absorption. Poses a special problem because of the insolubility of fats in water and because of lipolytic enzyme (these are a number of enzyme present in the pancreatic juice). DIGESTION OF LIPID:

6. These are solved in the gut by emulsification (a process of dispersion of lipid into small droplet by reducing surface tension.) , particularly by bile salt present in bile and pancreatic lipase. With the emulsification the rate of digestion is proportionally increase. Cont…….

7. The whole process of digestion of dietary lipids and its subsequent absorption may be arbitrarily divided into three phases; Preparatory phase Transport phase Transportation phase Phases of digestion and absorption:

8. During the preparatory phase , the overall digestive system of body prepare to digest and absorb the lipid in the body. Its digestion is divided on the basis of different parts of the body Digestion in mouth and stomach Digestion in small intestine 1. Preparatory phase:

9. It was believed that little or no fat digestion take place in the mouth, but recently a lipase has been detected called lingual lipase which is secreted by the dorsal surface of the tongue ( Ebner’s gland) Digestion in mouth and stomach:

10. Its pH is 2.0-7.5 Its activity is continued in stomach, and also where the pH value is low. Due to retention of food bolus for 2-3 hours, about 30% dietary TG( Triacyl glycerol) More active on TG and more specific for ester linkage at position-3 rather than position-1. Milk fat contain short and medium fatty acid . So milk fat appears to be the best substrate for this enzyme. Lingual lipase:

11. More soluble, this short fatty acid and can be absorbed directly from the stomach wall and enter the portal vein. After the action of lingual lipase it pass to the stomach and the action of gastric lipase start. Conti…

12. There is evidence of presence of small amount of gastric lipase in gastric secretion. The overall digestion of fats , brought about by gastric lipase is negligible because; No emulsification occur. Small quantity of enzyme. It need ca++. pH (not conductive which is highly acidic) Gastric lipase:

13. Liquid substance released by lever from gall bladder to main pancreatic duct and then goes to duodenum. It contain bile salt. Store in the gall bladder and when necessary move to the duodenum. The bile salt break down the large lipid molecule into smaller through emulsification process. Bile :

14. They are not enzymes but there are some special compounds which helps in digestion and absorption of lipid. Phasphoglycerolipids (emulsification). Bile acid (colic acid) which help to prevent the enzymatic activity (reverse) and form micelles. Conti…

15. Some fatty acid which are not absorbed into the cell freely, aggregate with bile salt, cholesterol and lipid soluble substances to create a substance called micelles. Conti….

16. Small intestine is the major site of fat digestion. Its due to the presence of; Lipase ( Steapsin ). Bile salts. These two inter the intestine through pancreatic and bile ducts to duodenum. ii. Digestion in small intestine

17. For the stimulation of pancreatic juice secretion is Passage of an acid gastric contents (acid chyme ) into duodenum. By secretion of GI hormones, secretin and CCK_PZ. Conti….

18. The function of secretion in the small intestine is to increase the secretion of electrolytes and fluid component of pancreatic juice. HEPATOCRININ: Function of H epatocrinin is to released by the intestinal mucosa stimulates more bile formation which is relatively poor in the bile salt content. Secretin :

19. To stimulate the secretion of pancreatic enzyme. cholecystokinin of CCK-PZ: To cause contraction of the gallbladder and discharge of bile is also stimulated by secretin and bile salt themselves. the above sequence of events prepares the small intestine for the digestion of fats. Pancreozymin of CCK-PZ:

20. These are a number of enzyme present in the pancreatic juice. Pancreatic lipase Phospholipase A 2 Cholesterol esterase. Pancreatic lipase is most important which hydrolyze TG containing short and long chain fatty acid. LIPOLYTIC ENZYME:

21. TG hydrolyze through lipase to remove one fatty acid at the one terminal to form α , β - diglyceride . At the other step the other fatty acid is removed and α , β - diglycerid is converted to β - diglycerid . the middle fatty acid is not easily removable so first it will convert into 1 or 3 position through isomarase and then remove to form glycerol and fatty acid. Mode of action of Pancreatic lipase:

22. The product of preparatory phase ( fatty acid and monoglyceride ) enter the microvilli ( enterosytes cell )and apical pole of absorptive epithelial cells by “simple diffusion” through cell membrane. in this phase short , medium and unsaturated fatty acid are more absorbed than the long chain fatty acid. The product of fat digestion next appear to be taken up by the SER and resynthesised into TG again by enzymatic action. 2. Transport phase: .

23. The rapid removal of product and their synthesis into TG in intestinal epithelial cell, maintains a sharp gradient of concentration with in the mucosal cell that favors the continued rapid diffusion into the cell from intestinal lumen. Conti…

24. Sequence of events that occur inside the intestinal mucosal cell are; with in the intestinal cell, α - monoglycerid are further hydrolyzed by intestinal lipase to produce free fatty acid and glycerol. Intestinal lipase: A lipase distinct from that of the pancreatic lipase is present in intestinal mucosal cell. TRANSPORTATION PHASE:

25. Fatty acid absorbed from intestinal lumen and fatty acid formed from hydrolysis of α - monoglycerid are activated to “ Acyl-CoA ”. An ATP-dependent thiokinase . Principal action:

26. Pancreatic juice contain a type of enzyme called phaspholipase A2( Lecithinase ). It is an esterase, and secreted as in inactive zymogene proenzyme, which is changed to active form, by hydrolysis of peptide molecule with the help of trypsin . Digestion and absorption of phospholipids:

27. In the presence of bile salt and Ca++, the active phaspholipase A2 hydrolyses the ester linkage between fatty acid and secondary alcohol group of position-2 of glycerol in phospholipids molecule so that free fatty acid and lysophospholipid are formed and are absorbed. Conti….

28. Pancreatic juice contain an enzyme cholesterol esterase, which may either catalyze the estrification of free cholesterol with fatty acid or it may catalyze opposite reaction. The cholesterol appears to be absorbed from the intestine almost entirely in free form. Digestion and absorption of cholesterol:

29. Nevertheless , 85 to 90% of cholesterol in the lymph is found to be in estrified form, indicating that estrification of cholesterol must take place with in the mucosal cell of intestine. Absorption of cholesterol has been reported to be facilitated by presence of unsaturated fatty acid and bile are necessary for absorption of cholesterol. Certain plant sterol like sitosterol and stigmasterol are not absorbed, rather their presence can inhibit cholesterol absorption. Conti….