lipids_233455668899076544553879848657.pptx

Lipids

1. Digestion, Absorption and Metabolism of Lipids Dr. M. Ambika Prasad, Dr. Ckalyan , Dr. E. Muralnath , Dr. K. Sravan Pragna & Dr. Saisruthi

2. LIPIDS IN DIET Lipids are mostly consumed in the form of neutral fats, which are also termed as as triglycerides. Triglycerides consist of glycerol nucleus and free fatty acids. Triglycerides form the major constituent in foods of animal origin and much less in foods of plant origin. 4) Apart from triglycerides, usual diet also consists of small quantities of cholesterol and cholesterol esters.   Dietary fats are c ategorized into two types: 1. Saturated fats 2. Unsaturated fats.

3. SATURATED FATS Saturated fats are the fats which co nsist of triglycerides formed from only saturated fatty acids. The fatty acids having maximum amount of hydrogen ions without any double bonds between carbon atoms are known as saturated fatty acids.

4. UNSATURATED FATS Fats containing unsaturated fatty acids are termed as unsaturated fats. The formation of u nsaturated fatty acids takes place with the help of fatty acids f ormed due to dehydrogenation of saturated fatty acids. Unsaturated fats are c ategorized into three types: 1. Monounsaturated fats 2. Polyunsaturated fats 3. Trans fats.

5. 1. Monounsaturated Fats Unsaturated fats which contain one double bond between the carbon atoms are termed as monounsaturated fats. 2. Polyunsaturated Fats Unsaturated fats with more than one double bond between the carbon atoms are known as polyunsaturated fats. Polyunsaturated fats belong to the family of essential fatty acids (fatty acids needed in diet).

6. Polyunsaturated fats are of two types: 1. Omega-3 fats or omega­3 fatty acids having double bond in the third space from the end of the carbon chain 2. Omega-6 fats or omega­6 fatty acids having double bond in the sixth space from the end of the carbon chain. Both omega-3 and omega-6 fatty acids shoe beneficial effect to the body. Whatewver it may be, , consuming too much of omega­6 fatty acids leads to hazards than benefits. That is why , the diet c on sisting of 3 : 1 ratio of omega-6 to omega-3 fatty acids is often recommended by experts.

7. 3. Trans Fats Trans fats or trans fatty acids are unsaturated fatty acids, with molecules containing trans (across or opposite side) double bonds between carbon atoms.   Lipolytic Enzymes in Pancreatic Juice Pancreatic lipase is the most important enzyme for the digestion of fats. Other lipolytic enzymes of pancreatic juice are cholesterol ester hydrolase, phospholipase A and phospholipase B . Lipolytic Enzyme in Succus Entericus Intestinal lipase is the only lipolytic enzyme observed in succus entericus .

8. FINAL PRODUCTS OF FAT DIGESTION Fatty acids, cholesterol and monoglycerides are the final products of lipid digestion. ABSORPTION OF LIPIDS Monoglycerides, cholesterol and fatty acids from the micelles gain an entry into the cells of intestinal mucosa by simple diffusion.   From here, further transport happens as follows: ) In the mucosal cells, most of the monoglycerides are c hanged into triglycerides. The formation of t riglycerides occus with the help of re-esterification of fatty acids with more than 10 to 12 carbon atoms. Some of the cholesterol is also esterified.

9. DIGESTION OF LIPIDS The digestion of lipids happens with the help of lipolytic enzymes. IN THE MOUTH Saliva con sists of lingual lipase. The secrtetion of this enzyme takes place with the help of lingual glands of mouth and swallowed along with saliva. That is why , the lipid digestion does not start in the mouth

10. IN THE STOMACH Gastric lipase or tributyrase is the lipolytic enzyme observed in gastric juice .   IN THE INTESTINE Almost all the lipids are digested in the small intestine due to the availability of bile salts, pancreatic lipolytic enzymes and intestinal lipase.

11. Role of Bile Salts Bile salts play an important role in the digestion of lipids   STORAGE OF LIPIDS The storage of lipids happens in adipose tissue and liver. Fat stored in adipose tissue is termed as neutral fat or tissue fat. When chylomicrons are traveling through capillaries of adipose tissue or liver, the enzyme known as lipoprotein lipase present in the capillary endothelium hydrolyzes triglycerides of chylomicrons into free fatty acids (FFA) and glycerol. FFA and glycerol gain an entry into the fat cells (adipocytes or lipocytes

12. Then, the FFA and glycerol are again c hanged into triglycerides and stored in these cells. 5) Other contents of chylomicrons namely cholesterol and phospholipids, which are released into the blood combine with proteins and result in the formation of lipoproteins. 6) When other tissues of the body require energy, triglycerides stored in adipose tissue is hydrolyzed into FFA and glycerol. The transportation of FFA happens in the the body tissues through blood.

13. TRANSPORT OF LIPIDS IN BLOOD – LIPOPROTEINS The transportation of f ree fatty acids happens in the blood particularly in combination with albumin. Other lipids are transported in the blood, in the form of lipoproteins. LIPOPROTEINS Lipoproteins are the small particles in the blood which C cnsist of cholesterol, phospholipids, triglycerides and proteins. Proteins are beta­globulins termed as apoproteins.

14. Classification of Lipoproteins Lipoproteins are c ategorized into four types on the basis of their density: 1. Very-low-density lipoproteins (VLDL): Contain high concentration of triglycerides (formed from FFA and glycerol) and moderate concentration of cholesterol and phospholipids 2. Intermediate-density lipoproteins (IDL): Formed by the removal of large portion of triglycerides from VLDL with the help of lipoprotein lipase.

15. .3. Low-density lipoproteins (LDL): Formed from IDL because of the complete elimination of triglycerides. These lipoproteins con sist of only cholesterol and phospholipids 4. High-density lipoproteins (HDL): Con sist of high concentrations of proteins with low concentration of cholesterol and phospholipids. The synthesis of a ll the lipoproteins are happens in liver. The synthesis of HDL also happens in intestine also.

16. Functions of Lipoproteins Primary function of lipoproteins is to transport the lipids via blood to and from the tissues.

17. Importance of Lipoproteins High-density lipoprotein High­denisty lipoprotein (HDL) is referred as the ‘good cholesterol’ because it carries cholesterol and phospholipids from tissues and organs back to the Liver particularly for degradation and elimination. It inhibits the deposition of cholesterol on the walls of arteries, by carrying cholesterol away from arteries to the liver. High level of HDL is a good indicator of a healthy heart, because it decreases the blood cholesterol level. HDL also assists regarding the normal functioning of some hormones and certain tissues of the body. It is also helpful regarding the formatioin of formation of bile in liver.

18. Low-density lipoprotein Low­density lipoprotein (LDL) is treated as the ‘bad cholesterol’ because it carries cholesterol and phospholipids from the liver to different areas of the body, viz. muscles, other tissues and organs such as heart.

19. ADIPOSE TISSUE Adipose tissue or fat is a loose connective tissue that forms the storage site of fat particularly in the form of in the form of triglycerides. It consists of adipocytes, which are also treated as fat cells or lipocytes. Obesity does not depend on the body weight, but on the amount of body fat, specifically adipose tissue. Adipose tissue is of two types, white adipose tissue and brown adipose tissue.  

20. WHITE ADIPOSE TISSUE OR WHITE FAT The distribution of white adipose issue White adipose tissue occurs through the body beneath the skin, forming subcutaneous fat. It also covers the internal organs. The formation of t his adipose tissue occurs with the help of fat cells which are unilocular, i.e. these cells contain one large vacuole filled with fat.

21. Functions of White Adipose Tissue White adipose tissue exhibits three functions: 1. ) Storage of energy: M ajor function of white adipose tissue is specifically the storage of lipids. Utilization or storage of fat is controlled by hormones, especially insulin, based on the blood glucose level. If the blood glucose level enhances , insulin activates synthesis and storage of fat especially in white adipose tissue On the other hand, if blood glucose level reduces insulin causes release of fat from adipose tissue. Released fat is utilized for the purpose of energy

22. 2. Heat insulation: Insulation function is because of the presence of adipose tissue beneath the skin (subcutaneous adipose tissue)   3. Protection of internal organs: White adipose tissue protects the body and internal organs by covering them and by behaving like a mechanical cushion.

23. BROWN ADIPOSE TISSUE OR BROWN FAT Brown adipose tissue is a specialized form of adipose tissue, exhibiting the function opposite to that of white adipose tissue. It is observed only in certain areas of the body such as back of neck and intrascapular region. It is abundant particularly in infants forming about 5% of total adipose tissue. After infancy, brown adipose tissue disappears in a gradual manner and forms only about 1% of total adipose tissue in adults. It is formed by fat cells which are multilocular, i.e. these cells co nsist of many small cholesterol and phospholipids enhances due to removal of triglycerides

24. Functions of Brown Adipose Tissue Brown adipose tissue does not store lipids but generates heat with the help of burning lipids. In infants and hibernating animals, brown adipose tissue plays an import ant role regarding the regulat ion of body temperature with the help of non-shivering thermogenesis. Heat production in brown fat plays an importasnt role regarding survival of infants and

25. It is because, the lipid in this tissue releases energy in a direct manner as heat. The mitochondria found in brown adipose tissue c on sist of a unique uncoupling protein treated as mitochondrial uncoupling protein 1 (UCP1). Also called thermogenin, this protein permits the controlled entry of protons without adenosine triphosphate (ATP) synthesis, in order to generate heat.  

26. METABOLISM OF LIPIDS LIPID PROFILE 1 Lipid profile is a group of blood tests which are carried out to estimate the risk of coronary artery diseases (CAD). Results of lipid profile are treated as good indicators of whether someone is prone to develop stroke or heart attack, caused by atherosclerosis. In order to plan the course of treatment, the results of the lipid profile are associated with age, sex and other risk factors of heart disease. Tests included in lipid profile are total cholesterol, triglyceride, HDL, LDL, VLDL and total cholesterol – HDL ratio. Total cholesterol to HDL ratio i playas an imortant role predicti on of atherosclerosis and CAD. It is obtained by dividing total cholesterol by HDL. High total cholesterol and low HDL enhances the ratio. The increase in the ratio is undesirable. Conversely, high HDL and low total cholesterol lowers the ratio and the decrease in the ratio is also desirable.

27. LONG QUESTIONS 1. What are the different types of salivary glands? Explain about the composition, functions and regulation of secretion of saliva. 2. Describe the composition and functions of gastric juice and explain briefly about the hormonal regulation of gastric secretion. 3. Describe the different phases of gastric secretion with experimental evidences. 4. Narrate the composition, functions and regulation of secretion of pancreatic juice. 5. Describe the composition, functions and regulation of secretion of bile. Mention the differences between the liver bile and gallbladder bile. Add a brief description on enterohepatic circulation. 6. Write an essay about succus entericus. 7. Explain in detail about gastric motility. What are the factors influencing gastric emptying? 8. Describe in detail, the gastrointestinal movements.

28. SHORT NOTES 1. Properties and composition of saliva. 2. Functions of saliva. 3. Nerve supply to salivary glands. 4. Glands of stomach. 5. Functions of stomach. 6. Properties and composition of gastric juice. 7. Functions of gastric juice 8. Mechanism of secretion of hydrochloric acid in stomach. 9. Pavlov’s pouch. 10. Sham feeding.

29. 11. Cephalic phase of gastric secretion. 12. Gastrin. 13. Roles of h ormones on stomach. 14. FTM. 15. Peptic ulcer. 16. Exocrine function of pancreas. 17. Properties and composition of pancreatic juice. 18. Functions of pancreatic juice. 19. Regulation of exocrine function of pancreas. 20. Steatorrhea.

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