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LIPID DIGESTION by GROUP 2. Study well DAA. :)

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  • There are at least five hormones that aid and regulate the digestive system in mammals. There are variations across the vertebrates, as for instance in birds. Arrangements are complex and additional details are regularly discovered. For instance, more connections to metabolic control (largely the glucose-insulin system) have been uncovered in recent years. Gastrin  - is in the  stomach  and stimulates the  gastric glands  to secrete  pepsinogen  (an inactive form of the enzyme  pepsin ) and  hydrochloric acid . Secretion of gastrin is stimulated by food arriving in stomach. The secretion is inhibited by low  pH  . Secretin  - is in the  duodenum  and signals the secretion of sodium bicarbonate in the  pancreas  and it stimulates the  bile secretion in the  liver . This hormone responds to the acidity of the chyme. Cholecystokinin  (CCK) - is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the  gall bladder . This hormone is secreted in response to fat in chyme. Gastric inhibitory peptide  (GIP) - is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach. Another function is to induce  insulin secretion. Motilin  - is in the duodenum and increases the  migrating myoelectric complex  component of gastrointestinal motility and stimulates the production of  pepsin .
  • The key players in these two transformations are bile acids and pancreatic lipase both of which are mixed with chyme and act in the lumen of the small intestine ENTROCYTES -intestinal absorptive cells, are simple columnar epithelial cells found in the small intestines and colon. A glycocalyx surface coat contains digestive enzymes. Microvilli on the apical surface increase surface area for the digestion and transport of molecules from the intestinal lumen
  • Bile acids are also necessary to solubilize other lipids, including cholesterol. Such coating with bile acids aids in breakdown of large aggregates or droplets into smaller and smaller droplets.
  • A variant of Phospholipase A 2 is secreted by the pancreas into the intestine. It hydrolyzes the ester linkage between the fatty acid and the hydroxyl on carbon 2 of phospholipids. Lysophospholipids , the products of Phospholipase A 2 reactions, are powerful detergents . 
  • Chylomicrons are large lipoprotein particles that consist of triglycerides (85-92%), phospholipids (6-12%), cholesterol (1-3%) and proteins (1-2%). [1] They transport dietary lipids from the intestines to other locations in the body. Chylomicrons are one of the five major groups of lipoproteins (chylomicrons, VLDL , IDL , LDL , HDL ) that enable fats and cholesterol to move within the water-based solution of the bloodstream.
  • LPL is a water soluble enzyme that hydrolyzes triglycerides in lipoproteins, such as those found in chylomicrons and very low-density lipoproteins (VLDL), into two free fatty acids and one monoacylglycerol molecule. Some of the components of the chylomicrons are "repackaged" into other lipoproteins, for example, some apolipoproteins are transferred to High-Density Lipoprotein(HDL), and the remaining chylomicron remnant particles are removed from the plasma by way of chylomicron remnant receptors present on the liver. LPL is attached to the luminal surface of endothelial cells in capillaries. It is most widely distributed in adipose, heart, and skeletal muscle tissue, as well as in lactating mammary glands.
  • VLDL enable lipids like cholesterol and triglycerides to be transported within the water-based bloodstream. five major groups of lipoproteins which, in order of sizes, largest to smallest, are chylomicrons, VLDL, IDL, LDL and HDL HDL is the smallest of the lipoprotein particles. They are the densest because they contain the highest proportion of protein to cholesterol. About one-fourth to one-third of blood cholesterol is carried by high-density lipoprotein (HDL). HDL cholesterol is known as "good" cholesterol, because high levels of HDL seem to protect against heart attack. Low levels of HDL (less than 40 mg/dL) also increase the risk of heart disease. Medical experts think that HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body. Some experts believe that HDL removes excess cholesterol from arterial plaque, slowing its buildup.
  • It is expressed in the liver and adrenal glands. One of the principal functions of hepatic lipase is to convert IDL to LDL. Each native IDL particle consists of protein that encircles various fatty acids, enabling, as a water-soluble particle, these fatty acids to travel in the aqueous blood environment as part of the fat transport system within the body they contain primarily a range of triacylglycerols and cholesterol esters. LIPC encodes hepatic triglyceride lipase, which is expressed in liver. LIPC has the dual functions of triglyceride hydrolase and ligand/bridging factor for receptor-mediated lipoprotein uptake.
  • too much LDL (bad) cholesterol circulates in the blood, it can slowly build up in the inner walls of the arteries that feed the heart and brain. Together with other substances, it can form plaque, a thick, hard deposit that can narrow the arteries and make them less flexible. formed from the degradation of very low-density lipoproteins. enable fats and cholesterol to move within the water-based solution of the bloodstream
  • Biochem

    1. 1. LIPID DIGESTION Group 2 DAA De Vera, Antonio Jr. Paule, Michelle Noreen Rañola, Anna Patricia Jo Villafranca, Anna Kareninna
    2. 2. Lipid digestion Lipid digestion is the breakdown of dietary fats into smaller molecules of nutrients for the absorption of the body
    3. 5. BILE <ul><li>Produced by the liver </li></ul><ul><li>Stored and release by the gallbladder </li></ul>
    4. 8. Laboratory Experiment
    5. 9. Materials <ul><li>Litmus paper </li></ul>To determine whether any acids are formed on hydrolysis
    6. 10. <ul><li>Pancreatin </li></ul>A mixture of digestive enzymes. It contains protease, lipase, and amylase.
    7. 11. <ul><li>Disodium carbonate </li></ul>Provides an alkaline medium for the pancreatin
    8. 12. PROCEDURE <ul><li>Add 4ml thin Dari cream to each of 3 labeled test tubes. </li></ul><ul><li>To the first tube, add 0.5 of pancreatin and 2ml of Na2CO3 solution. </li></ul><ul><li>To the second tube add 0.5g of pancreatin. </li></ul><ul><li>On the third tube add 2cc of the Na2CO3 solution. </li></ul><ul><li>Keep the contents of the test tubes warm of the body temperature for about 1 hour, shaking them at intervals. </li></ul><ul><li>Place a piece of litmus paper in each tube to determine whether any acids are formed on hydrolysis. Observe and record the results. </li></ul>
    9. 13. IDEAL RESULTS TEST TUBE CONTAINS: Litmus Paper Color Result pH 1 <ul><li>4ml thin Dari cream </li></ul><ul><li>0.5g of pancreatin </li></ul><ul><li>2ml Na2CO3 sol’n </li></ul>Red Litmus – RED Blue Litmus – RED Acidic 2 <ul><li>4ml thin Dari cream </li></ul><ul><li>0.5g of pancreatin </li></ul>Red Litmus – BLUE Blue Litmus – BLUE Basic 3 <ul><li>4ml thin Dari cream </li></ul><ul><li>2cc Na2CO3 sol’n </li></ul>Red Litmus – BLUE Blue Litmus – BLUE Basic
    11. 15. TEST DESCRIPTION POSITIVE RESULT NEGATIVE RESULT GREASE SPOT TEST Some oil and some water are smeared onto a piece of paper. Some time later, the water smear would become not translucent. But the smear of oil would keep translucent for a long time. formation of translucent spot on the paper. No Color Change SUDAN IV TEST Sudan red is a fat-soluble dye that stains lipids red. Using Sudan red can show the amount and the location of lipids. Red No Color Change
    13. 17. POST LAB (cont.) <ul><li>1.) What are the enzymes used in Lipid Digestion? </li></ul><ul><ul><ul><li>Lipases </li></ul></ul></ul><ul><ul><ul><ul><li>Pancreatic Lipase </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Lipoprotein Lipase </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Hepatic-triglyceride lipase (LIPC) </li></ul></ul></ul></ul>
    14. 18. POST LAB (cont.) <ul><li>2.) What are the similarities and differences of these enzymes? </li></ul>
    15. 19. Name Gene Location Description pancreatic lipase PNLIP digestive juice In order to exhibit optimal  enzyme  activity in the gut lumen, HPL requires another protein,  colipase , which is also secreted by the pancreas. lingual lipase   ? digestive juice -
    16. 20. hepatic lipase LIPC endothelium Hepatic lipase acts on remaining  lipids  carried on lipoproteins in the blood to regenerate LDL ( low density lipoprotein ). lipoprotein lipase LPL  or &quot;LIPD&quot; endothelium Lipoprotein lipase  functions in the  blood  to act on  triacylglycerides carried on VLDL (very low density  lipoprotein ) so that cells can take up the freed  fatty acids . gastric lipase LIPF digestive juice Functions in the infant at a near-neutral pH to aid in the digestion of lipids
    17. 21. POST LAB (cont.) <ul><li>3.) What are the factors that would bring about Lipid Digestion? </li></ul><ul><li>Bile plays a key role in the digestion of lipids (fats). It takes part in the emulsification of fats, making it possible for them to be digested. Bile helps to emulsify fats (increases its solubility in water), and aid in their absorption in the small intestine. </li></ul><ul><li>Lipase converts triglycerides into monoglycerides (individual fatty acids) and gycerol. </li></ul>
    18. 22. POST LAB (cont.) <ul><li>4.) Trace the pathway of Lipid Digestion. </li></ul><ul><li>Fat Digestion Overview </li></ul><ul><li>Mouth and salivary glands </li></ul><ul><li>Melting Fat; </li></ul><ul><li>Lingual lipase </li></ul><ul><li>  </li></ul><ul><li>Stomach </li></ul><ul><li>Lingual Lipase active in low pH </li></ul><ul><li>Hydrolysis low; Milk fat better </li></ul><ul><li>Gastric Lipase – low activity </li></ul><ul><li>  </li></ul><ul><li>Small Intestine </li></ul><ul><li>Emulsification – bile </li></ul><ul><li>Pancreatic and Intestinal Lipases </li></ul><ul><li>Fatty acids </li></ul><ul><li>Mono and Diglycerides </li></ul><ul><li>  </li></ul><ul><li>Large Intestine </li></ul><ul><li>Reabsorption of bile and some fatty acids </li></ul><ul><li>Losses in feces </li></ul>
    19. 23. POST LAB (cont.) <ul><li>5.) What tests are used to detect the completeness of Lipid Digestion? </li></ul><ul><li>Grease spot test /Brown paper test As we all know from experience, lipids leave translucent spots (grease spots) on unglazed brown paper bags. </li></ul><ul><li>Sudan Red test Sudan red is a fat-soluble dye that stains lipids red. Using Sudan red can show the amount and the location of lipids. </li></ul>
    20. 24. POST LAB (cont.) <ul><li>6.) What are the factors affecting Lipid Digestion? </li></ul><ul><ul><ul><li>Enzyme Activity </li></ul></ul></ul><ul><ul><ul><li>Digestive Hormone </li></ul></ul></ul><ul><ul><ul><li>pH </li></ul></ul></ul><ul><ul><ul><li>Weak acidic – Mouth, Pharynx, esophagus </li></ul></ul></ul><ul><ul><ul><li> Alkaline – Small intestine </li></ul></ul></ul>
    22. 26. In order for the triglyceride to be absorbed, two processes must occur: <ul><ul><ul><li>EMULSIFICATION </li></ul></ul></ul><ul><ul><li>Large aggregates of dietary triglyceride, which are virtually insoluble, must be broken down physically and held in suspension. </li></ul></ul>
    23. 27. <ul><ul><li>2. ENZYMATIC DIGESTION </li></ul></ul><ul><ul><li>Triglyceride molecules must be enzymatically digested to yield: </li></ul></ul><ul><ul><ul><ul><li>Monoglyceride </li></ul></ul></ul></ul><ul><ul><ul><ul><li>fatty acids </li></ul></ul></ul></ul><ul><ul><ul><ul><li>-both of which can efficiently diffuse or be transported into the enterocyte </li></ul></ul></ul></ul>
    24. 28. I. Emulsification <ul><li>Bile acids </li></ul><ul><li>- play their first critical role in lipid assimilation by promoting emulsification </li></ul><ul><ul><li>- both hydrophilic and hydrophobic domains </li></ul></ul><ul><ul><li>On exposure to a large aggregate of triglyceride </li></ul></ul>HYDROPHOBIC PORTION HYDROPHILIC PORTION Intercalate into the lipid Remains at the surface
    25. 29. II.Hydrolysis <ul><li>Pancreatic lipase </li></ul><ul><ul><li>predominantly hydrolyzes triglyceride into monoglyceride and free fatty acids </li></ul></ul><ul><ul><li>A protein colipase is required to aid binding of the pancreatic lipase at the lipid-water interface </li></ul></ul>
    26. 30. Cont… <ul><ul><li>The activity of this enzyme is to clip the fatty acids at positions 1 and 3 of the triglyceride, leaving two free fatty acids and a 2-monoglyceride . </li></ul></ul>
    27. 31. III. Micelle Formation <ul><ul><li>As monoglycerides and fatty acids are liberated through the action of lipase, they retain their association with bile acids and complex with other lipids to form structures called micelles </li></ul></ul><ul><ul><li>Micelles are essentially small aggregates of mixed lipids and bile acids suspended within the ingesta. </li></ul></ul><ul><ul><li>As the ingesta is mixed, micelles bump into the brush border of small intestinal enterocytes, and the lipids, including monoglyceride and fatty acids, are taken up into the epithelial cells. </li></ul></ul>
    28. 32. Cont… <ul><li>Monoacylglycerols, fatty acids, and cholesterol are absorbed by intestinal epithelial cells. </li></ul><ul><ul><li>Within intestinal epithelial cells, triacylglycerols are resynthesized from fatty acids and monoacylglycerols. </li></ul></ul>
    29. 33. Absorption and Transport into Blood <ul><li>The major products of lipid digestion: </li></ul><ul><ul><li>fatty acids and 2-monoglycerides </li></ul></ul><ul><ul><ul><li>enter the enterocyte by simple diffusion across the plasma membrane. </li></ul></ul></ul><ul><ul><ul><li>Once inside the enterocyte, fatty acids and monoglyceride are transported into the endoplasmic reticulum </li></ul></ul></ul><ul><ul><ul><ul><li>where they are used to synthesize triglyceride </li></ul></ul></ul></ul>
    30. 34. Cont… <ul><li>Beginning in the endoplasmic reticulum and continuing in the Golgi, triglyceride is packaged with cholesterol, lipoproteins and other lipids into particles called chylomicrons . </li></ul>
    31. 36. Pathways of Lipid Transport
    32. 37. The Pathways of Lipid Transport <ul><li>Three main pathways responsible for the generation and transport of lipids within the body: </li></ul><ul><ul><li>Exogenous (Dietary) Lipid Pathway </li></ul></ul><ul><ul><li>Endogenous Pathway </li></ul></ul><ul><ul><li>Reverse Cholesterol Transport </li></ul></ul>
    33. 38. Exogenous (Dietary) Lipid Pathway <ul><li>Following digestion and absorption of dietary fat, Triglycerides(TG) and cholesterol are packaged to form chylomicrons in the epithelial cells of the intestines. </li></ul><ul><li>- Chylomicrons circulate through the intestinal lymphatic system. </li></ul><ul><li>- In the blood, circulating chylomicrons interact at the capillaries of adipose tissue and muscle cells releasing TG to the adipose tissue to be stored and available for the body's energy needs. </li></ul>
    34. 39. Cont… <ul><li>Enzyme : Lipoprotein lipase (LPL) </li></ul><ul><li>Cofactor : Apo-CII </li></ul><ul><li>Action : hydrolyzes the TG in lipoproteins </li></ul><ul><ul><li>- such as those found in chylomicrons and Very Low-Density Lipoproteins (VLDL) </li></ul></ul><ul><ul><li>Products : </li></ul></ul><ul><ul><li>2 free fatty acids and 1 monoacylglycerol </li></ul></ul>
    35. 41. Endogenous Pathway <ul><li>involves the liver synthesizing lipoproteins. </li></ul><ul><li>TG and cholesterol ester are generated by the liver and packaged into Very low-density lipoprotein (VLDL) particles and then released into the circulation. </li></ul><ul><li>VLDL is then processed by LPL in tissues to release fatty acids and glycerol. </li></ul>
    36. 42. Cont… <ul><li>The fatty acids are taken up by: </li></ul><ul><ul><li>muscle cells - for energy </li></ul></ul><ul><ul><li>adipose cells - for storage. </li></ul></ul>
    37. 43. Very-Low Density lipoprotein <ul><li>Once processed by LPL, the VLDL becomes a VLDL remnant. </li></ul><ul><li>The majority of the VLDL remnants are taken up by the liver via the Low-Density lipoprotein receptor </li></ul><ul><li>the remaining remnant particles become Intermediate-Density lipoprotein (IDL) , a smaller, denser lipoprotein than VLDL. </li></ul>
    38. 44. Intermediate-Density Lipoprotein <ul><li>The fate of some of the IDL particles requires them to be reabsorbed by the liver </li></ul><ul><ul><li>Again, by the Low-density lipoprotein receptor </li></ul></ul><ul><ul><li>however, other IDL particles are hydrolyzed in the liver by hepatic-triglyceride lipase to form Low-Density Lipoprotein (LDL) , a smaller, denser particle than IDL. </li></ul></ul>
    39. 45. Low-Density Lipoprotein <ul><li>the main carrier of circulating cholesterol within the body </li></ul><ul><li>is used by extra-hepatic cells for cell membrane and steroid hormone synthesis </li></ul><ul><li>Much of the LDL particles are taken up by LDL receptors in the liver; </li></ul><ul><li>the remaining LDL is removed by way of scavenger pathways at the cellular level. </li></ul>
    40. 46. Cont… <ul><li>As LDL is taken up by receptors, free cholesterol is released and accumulates within the cells </li></ul><ul><ul><li>acyl-CoA cholesterol acyltransferase, which esterifies free cholesterol into cholesterol ester, storing cholesterol in the cell. </li></ul></ul>
    41. 48. Reverse Cholesterol Transport <ul><li>the process by which cholesterol is removed from the tissues and returned to the liver </li></ul><ul><li>High-Density Lipoprotein (HDL) is the key lipoprotein involved </li></ul><ul><li>for the transfer of cholesteryl esters between lipoproteins </li></ul>
    42. 49. Cont… <ul><li>HDL is formed through a maturation process of a series of conversions (known as the &quot;HDL cycle&quot;) </li></ul><ul><ul><li>to attract cholesterol from cell membranes and free cholesterol to the core of the HDL particle </li></ul></ul>
    43. 50. Cont… <ul><li>The exact mechanism by which the HDL delivers cholesterol esters to the liver is not well understood BUT; several mechanisms have been suggested. This Include: </li></ul><ul><li>The action of cholesteryl ester transfer protein </li></ul><ul><ul><li>which transforms HDL into a TG-rich particle that interacts with hepatic-triglyceride lipase </li></ul></ul><ul><ul><li>Cholesterol ester-rich HDL may also be taken up directly by the receptors in the liver </li></ul></ul><ul><ul><li>Another mechanism may be that cholesterol esters are delivered directly to the liver for uptake without catabolism of the HDL cholesterol particle </li></ul></ul>