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Questions and Answers
What is the primary difference between short-chain fatty acids and long-chain fatty acids in terms of absorption?
What is the term for the daily excretion of fat in feces greater than 6 gm per day?
What is the primary component of chylomicrons that are responsible for carrying dietary lipids from the intestine into the circulation?
What is the primary reason why milk fat and coconut oil are therapeutically useful in malabsorption syndromes?
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What is the term for the abnormal connection between the urinary tract and lymphatic drainage system of the intestine, resulting in a milky appearance of urine?
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What is the primary role of apo protein B48 in the absorption of dietary lipids?
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What is the primary mechanism by which short-chain fatty acids are absorbed into the bloodstream?
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What is the primary consequence of defective absorption of lipids in the intestine?
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What is the primary difference between chylomicrons and mixed micelles in terms of their composition?
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What is the primary reason why pancreatic lipase is essential for the absorption of dietary lipids?
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Study Notes
Lipid Digestion and Absorption
- Main dietary lipids: Triacylglycerol, Cholesterol, Phospholipids
- Recommended daily fat intake: 20-35% of Total Caloric Intake (TCI)
- Digestion in Stomach:
- Lingual lipase from the mouth enters stomach and continues to be active in stomach with an optimum pH of 2.5-5
- Acts on short chain triglycerides (SCT) present in milk, butter, and ghee
- Gastric lipase is acid stable with an optimum pH of 5.4
- Up to 30% digestion of triglycerides occurs in stomach
Emulsification and Bile Salts
- Emulsification is a pre-requisite for lipid digestion, reducing surface tension and increasing surface area of droplets
- Favoured by: Bile salts (detergent action), Peristalsis (mechanical mixing), and Phospholipids
- Bile salts: Sodium glycocholate and Sodium taurocholate lower surface tension and emulsify fat droplets
- Bile salts break down large aggregates into smaller droplets, increasing surface area for lipase action
Lipolytic Enzymes and Digestion of Triglycerides
- Pancreatic lipase with co-lipase, Cholesterol esterase, and Phospholipase A2 are lipolytic enzymes in the intestine
- Pancreatic lipase hydrolyses triglycerides to form 2-monoacyl glycerol and two fatty acids
- Isomerase shifts fatty acid position 2 to 1
Formation of Chylomicrons
- Digested products are incorporated into Chylomicrons, consisting of Triacylglycerol, Cholesterol ester, Phospholipids, and Apo proteins B48 and A
- Chylomicrons are transported through lacteals into the thoracic duct and then emptied into lymph circulation
Absorption of Short Chain Fatty Acids
- Short chain fatty acids (SCF) from milk, butter, and ghee do not require re-esterification and are directly absorbed into blood vessels
- Medium chain fatty acids (MCF) from coconut oil and mother's milk are also better absorbed than long chain fatty acids
Abnormalities in Absorption of Lipids
- Defective digestion: Steatorrhea (>6g fat excretion per day) in pancreatic diseases
- Defective absorption: Coeliac disease, Sprue, Crohn's disease, Surgical removal of intestine, and Obstruction of bile duct
- Triglycerides with short chain and medium chain fatty acids are digested and absorbed properly in malabsorption syndromes
- Chyluria: Abnormal connection between urinary tract and lymphatic drainage system of the intestine, resulting in milky urine due to lipid droplets
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Description
Learn about the main dietary lipids, recommended daily fat intake, and the digestion process in the stomach, including the role of lingual lipase and gastric lipase.
