Question

In Mediterranean countries, it is traditionally recommended to drink a glass of olive oil per day to stay healthy. Consider that olive oil is made of 100% of triglycerides. Among the fatty acids contained in these triglycerides, 70% are oleic acid (monounsaturated fatty acid with 18 carbons), 10% are linoleic acid (polyunsaturated fatty acid (2 unsaturations) with 18 carbons) and linolenic acid (polyunsaturated fatty acid (3 unsaturations) with 18 carbons), 10% are palmitic acid (saturated fatty acid with 16 carbons), and 10% are stearic acid (saturated fatty acid with 18 carbons).

B. Explain how these triglycerides are digested in the intestine.

C.Explain how these lipids are distributed to peripheral tissues (explain in detail how these lipids are transported from the intestine to the peripheral tissues (or extra-hepatic tissues) : how they are transported in the bloodstream and how they are distributed to the peripheral tissues)

D. Explain the different fates of these fatty acids in the post-prandial period in the following organs: a) skeletal muscles, b) adipose tissue and c) the brain. For each metabolic pathway involved, name the pathway, give the initial substrate(s) and the final product(s) and the ultimate goal of each pathway (please do not describe the whole pathway!). Then, describe the limiting step(s) of each pathway: give the substrate and the product of each limiting reaction and the name of the enzyme that catalyzes each limiting reaction. Finally, briefly explain how these pathways are regulated during the post-prandial period. (13.5 marks)

Answer 1

Answer (b) Fats are digested with the help of lipase which helps in breaking the bonds of fatty acids.Fat digestion and absorption are done by bile salts,which helps in emulsification of fats and convert them to micells in the chyme.Bile acids play important role in lipid assimilation by emulsification. Bile acids are actually both hydrophobic and hydrophilic. On exposure to bigger molecules of triglyceride, the hydrophobic portions of bile acids cover the lipid, and the hydrophilic part remains at the surface. This coating with bile acids helps in breakdown of large molecules into smaller and smaller molecules.

Lipase is a water-soluble enzyme.lipase is present in the small intestine and act only on triglyeride droplets. Triglycerides converted to monoglycerides and fatty acids are formed by the action of lipase, bile acids form complex with other lipids to form structures called Micelles .Micelles are small aggregates of mixed lipids and bile acids. These micelles then go to brush border epithelium of small intestine.

Answer (c)

Small and medium size fatty acids are directly absorbed into the blood via intestinal capillaries and travel by the portal vein. Big size fatty acids are coated with cholesterol and protein forming chylomicron and this enters a lymphatic capillary and enters into bloodstream and goes firstly to subclavian vein bypassing the liver.