28 Questions
Which organ is primarily responsible for the majority of lipid digestion?
Small intestine
What is the main component of dietary lipids intake?
Triacylglycerol
Which enzyme is involved in lipid degradation by the pancreatic enzymes?
Pancreatic lipase
What is the fate of absorbed lipid molecules in the body?
Direct utilization by the tissues
What is the approximate daily intake of dietary lipids?
78-81 g/day
What is the remainder of dietary lipids intake, aside from Triacylglycerol?
Phospholipids and Glycolipids
What is a clinical manifestation of diseases involving defective lipid digestion and/or absorption?
Indigestion and malabsorption syndrome
What control pancreatic insufficiency?
Enzyme replacement therapy
Which enzyme is responsible for breaking down triacylglycerides into fatty acids and glycerol?
Pancreatic lipase
What is the main location for the primary contributors to lipid digestion?
Small intestine
What is the role of bile salts in the digestion process?
Emulsifying dietary lipids
Which hormone stimulates the release of bile and pancreatic enzymes?
Cholecystokinin (CCK)
What causes pancreatic insufficiency commonly observed in cystic fibrosis?
Thickening of pancreatic secretions
Which enzyme acts on phospholipids to produce lysophospholipids and free fatty acids?
Phospholipase A2
What is the role of co-lipase in lipid digestion?
Aiding in the activity of pancreatic lipase
Which enzyme hydrolyzes cholesterol esters into free cholesterol and fatty acids?
Cholesterol esterase
What do acid lipases help digest in neonates and patients with pancreatic insufficiency?
Milk fat due to their inability to produce or absorb sufficient pancreatic secretions.
What are the two hormones that control the lipid digestion process?
Cholecystokinin (CCK) and secretin.
Where does emulsification of dietary fats primarily occur?
Duodenum
Chylomicrons are synthesized in which organ?
Liver
Where is the primary site for the absorption of the end products of lipid digestion?
Small intestine
Which enzyme is responsible for the hydrolysis of triglycerides?
Pancreatic Lipase
In lipid digestion, what is the primary function of phospholipase A2?
Breaking down phospholipids
Which organ secretes cholesterol esterase?
Pancreas
What is the role of cholecystokinin (CCK) in the control of lipid digestion?
Acting on the gallbladder to release bile and on the pancreas to release enzymes
What happens to chylomicrons after their synthesis?
They are packaged as lipid droplets surrounded by a thin layer of apolipoprotein B-48 (apo B-48) and phospholipids.
What causes serum to become milky after a fatty meal?
Secretion of chylomicrons into systemic circulation.
What is the main function of mixed micelles in lipid absorption?
Direct absorption by brush border membrane of enterocytes.
Study Notes
- Gastric lipase is a digestive enzyme secreted in the mouth, but it starts working in the stomach due to the requirement of an acidic medium.
- Small intestine is where the main lipid digestion takes place, with the enzymes produced in the pancreas being the primary contributors.
- The key enzymes involved in lipid digestion in the small intestine are: Pancreatic Lipase, Co-lipase, Cholesterol esterase, Phospholipase A2, and Lysophospholipase.
- Pancreatic lipase is responsible for breaking down triacylglycerides into fatty acids and glycerol, with co-lipase aiding in its activity. Cholesterol esterase hydrolyzes cholesterol esters into free cholesterol and fatty acids. Phospholipase A2 acts on phospholipids to produce lysophospholipids and free fatty acids, while lysophospholipase converts lysophospholipids into glycerophospholipids and fatty acids.
- Lipases in the stomach (gastric lipase and lingual lipase) hydrolyze the triacylglycerides with short to medium chain fatty acids, enabling their digestion and absorption.
- Neonates and patients with pancreatic insufficiency rely on acid lipases for milk fat digestion due to their inability to produce or absorb sufficient pancreatic secretions.
- Bile salts play a crucial role in the digestion process by emulsifying dietary lipids, increasing their surface area, and making them available for enzyme digestion.
- Pancreatic lipase and co-lipase are essential for the degradation of triacylglycerides, while cholesterol esterase is responsible for cholesterol ester degradation. Phospholipids are digested by phospholipase A2 and lysophospholipase.
- Pancreatic insufficiency, commonly observed in cystic fibrosis, is caused by defective CFTR (cystic fibrosis transmembrane conductance regulator) and results in decreased secretion of chloride, increased reabsorption of sodium and water, and the thickening of pancreatic secretions, which eventually blocks the pancreatic duct, preventing the enzymes from reaching the intestine and causing malnutrition.
- Cholecystokinin (CCK) and secretin are two hormones that control the lipid digestion process by stimulating the release of bile and pancreatic enzymes, decreasing gastric motility, and neutralizing the pH of the small intestinal contents.
Explore the biochemical aspects of lipid digestion, including organs involved, enzymes required, and end products. Study the synthesis, secretion, and fate of chylomicron, as well as the clinical manifestations of diseases related to lipid digestion and absorption.
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