Metabolism of fat

Metabolism of fat

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  METABOLISM OF FAT BYPINKY RATHEE
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  Introduction Metabolism of fatinvolves catabolic and anabolic processes. catabolic processes that generate energy. anabolic processes that create biologically important molecules (cholestrol, triglycerides, phospholipids, and ketone bodies, lipoproteins).
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  Pathways for metabolismof fat The fat we eat help to enjoy food and also plays important role in body. Fat stores helps as cushion for vital organs and protect nerve cells. Fat is used in body by two pathways:- Endogenous pathway Exogenous pathway
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  Endogenous Pathway • Fatdigestion begins when a gland under the tongue secrets the fat- splitting enzyme lingual lipase. • Gastric lipase, secreted by cells in stomach wall act like a blender, churning and mixing stomach contents. • Together this emulsifies the fat by breaking up large fat globules into smaller ones, distributing them evenly. • It takes stomach longer to digest fats then carbohydrates or proteins, so higher fat meal make feel fuller, longer. Mouth and stomach:-
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  . • Fat digestionand absorption requires that the complex fat molecules be broken down into smaller & more manageable molecules. • Pancreatic Lipase, an enzyme secreted by pancreas chops liquid molecules into fatty acid molecules and glycerol molecules. • Fat does not dissolve in water, the fat molecule enter the duodenum in a mass form, which makes it impossible for the pancreatic lipase enzymes to attack them, since lipase is a water soluble enzyme and can only attack the surface of the fat molecules. Pancrease:-
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  . • bile isproduced in the liver and stored in the gall bladder, which enters the duodenum through bile duct. • Bile emulsifies fats-meaning, it disperses them into small droplets which then become suspended in the watery content of the digestive tract. • Emulsification allows lipase to gain easer access to fat molecules and thus accelerates their breakdown and digestion. • Lipase and other digestive juices breakdown the fat molecules into fatty acids and types of glycerol. Gall bladder:-
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  . • Absorption offat into the body, which takes 10-15 minutes, occurs through villi- finger like projections which cover the walls of the small intestine. • Inside each villi is a series of lymph vessels (lacteals) and blood vessels (capillaries). The lacteals absorb the fatty acids and glycerol into the lymphatic system which eventually drains into blood stream. Small Intestine:-
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  • The fattyacids are transported via the blood stream to the membranes of adipose cells, or muscle cells where they are either stored or oxidized for energy. • Fat is the body’s preferred source of energy and since only about 5% of absorbed fat the glycerol can be converted into glucose, a significant proportion of digested fat is typically stored as body fat in the adipose cells. • The glycerol part is absorbed by the liver and is either converted into glucose (gluconeogenesis) and used to help in the breakdown of glucose into energy (glycolysis). Absorption and transportation:- Absorption and transportation:-
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  Absorption and transportation:- Absorptionof fats takes place in the duodenum and are transported into the lymphatic system. Fat droplets mainly comprised of triglycerides are first emulsified by the bile salts. Emulsification makes the fat droplets smaller making them more easily digestable enzymatically. Pancreatic lipase digests the smaller, emulsified fat droplets into free fatty acids and mono- glycerides. The free fatty acids and mono-glycerides form micelles which migrate towards the brush border membrane. The micelles contain bile salts, and the free fatty acids and mono-glycerides leave the micelle and enter the epithelial cell. Inside the epithelial cell, the free fatty acids and mono-glycerides combine with protein to form chylomicrons (lipid + protein).the chylomicrons are selected into lymphatic system
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  Endogenous pathway Liver isthe main organ which helps in the fat metabolism. There are 5 types of lipoproteins:- •Chylomicrons •VLDL( very low density lipoprotein) •LDL (low density lipoprotein) •HDL (high density lipoprotein) •Free fatty acids
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  Cont… Every cell needscholestrol (main source of energy) so liver continuously produces VLDL. LDL are having decreased density of protein and increased density of lipids HDL go around body interacting with other lipids particles in cells and picking up stray cholestrols.
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  Cont… When cholestrol becomeoxydised it become sticky and stagnant over artery walls. In blood stream, macrophages helps in keeping up dead particles or debries, if arterial walls are diseased, more macrophages try to keep the endothelial intact. VLDL become degraded as they pull out various aspects of cholestrol & may result into LDL
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  Cont… LDL (primary cholestrol),macrophages grabthe LDL, as debries because of its oxydation & starts to feed on them and create a waxy atheroma causing hypercholesrolemia and dislipidemia. VLDL is inversely proportional to HDL. VLDL supplies triglycerides and cholestrol. 50% of cholestrol is degraded by bile.
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  Action of bile:- Fattymeal passes in duodenum, bile emulsify the fat More soluble fibres forms as jell and jell binds itself with the bile salts Jell holds those bile salts and take them in intestine and excrete through the feces Need for energy ,in starvation , ATP production is done by tri- glycerols present in adipose tisue Liver starts producing free fatty acids, triglycerols, and lipoproteins.
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