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Questions and Answers
Which enzyme found in the stomach has little significance in adults but acts on TAG of milk fats in neonates?
Which enzyme found in the stomach has little significance in adults but acts on TAG of milk fats in neonates?
What role do bile salts play in lipid metabolism?
What role do bile salts play in lipid metabolism?
The product of triacylglycerol hydrolysis by pancreatic lipase includes which of the following?
The product of triacylglycerol hydrolysis by pancreatic lipase includes which of the following?
Which phospholipase specifically removes fatty acids from C2 of phospholipids?
Which phospholipase specifically removes fatty acids from C2 of phospholipids?
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Which enzyme is responsible for degrading cholesterol esters?
Which enzyme is responsible for degrading cholesterol esters?
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What is the primary function of micelles in lipid metabolism?
What is the primary function of micelles in lipid metabolism?
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Which component is NOT part of chylomicron composition?
Which component is NOT part of chylomicron composition?
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Which enzyme catalyzes the conversion of acetyl-CoA to malonyl-CoA during fatty acid synthesis?
Which enzyme catalyzes the conversion of acetyl-CoA to malonyl-CoA during fatty acid synthesis?
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What is the end product of fatty acid synthesis that consists of 16 carbon atoms?
What is the end product of fatty acid synthesis that consists of 16 carbon atoms?
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During fatty acid synthesis, how many NADPH molecules are utilized in each reaction sequence to extend the fatty acid chain?
During fatty acid synthesis, how many NADPH molecules are utilized in each reaction sequence to extend the fatty acid chain?
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Study Notes
Lipids Metabolism: Digestion
-
Sites of Digestion:
- Mouth
- Stomach
- Small intestine
-
Enzymes in the Mouth:
- Saliva contains lingual lipase which breaks down short and medium chain fatty acids from milk fats. Lingual lipase activity continues in the stomach.
-
Enzymes in the Stomach:
- Lingual lipase and gastric lipase act on milk fat triglycerides (TAGs) in infants. This isn't significant in adults.
-
Enzymes in the Small Intestine:
- Bile salts are not enzymes but emulsify fats, increasing surface area for enzymes to act on.
- Pancreatic lipase and colipase are important enzymes. They break down triacylglycerol, removing fatty acids from carbons 1 and 3 to leave 2-monoacylglycerol. Free fatty acids are also a product.
- Other pancreatic enzymes include cholesterol esterase, and phospholipase A2.
Lipids Metabolism: Cholesterol Ester Digestion
- Cholesterol esters are broken down by cholesterol esterase, with bile salts needed for activation.
- The products of hydrolysis are cholesterol and fatty acids.
Lipids Metabolism: Phospholipid Digestion
- Phospholipids are digested by different types of phospholipases (A1, A2, C, and D).
- PLA2 removes a fatty acid from carbon 2, yielding lysophospholipids.
- PLA1 removes a fatty acid from carbon 1, yielding glycerophosphorylbase.
Lipids Metabolism: Absorption
- Large fatty molecules (lipids, cholesterol esters, etc.) and digestive products are absorbed through the intestinal epithelium.
- Micelles are aggregates of lipids formed in the small intestine to help in lipid absorption. These include glycerol, cholesterol, long-chain fatty acids, and fat-soluble vitamins that are combined in a way that the fat-soluble portions are in the center and the water-soluble portions are on the outside.
- Chylomicrons are formed in the intestinal cells (enterocytes). They are lipoproteins that transport absorbed lipids to the lymph system, ultimately going to the bloodstream. They contain triglycerides, cholesterol esters, and phospholipids.
Lipids Metabolism: Lipogenesis (Simple Lipid Metabolism)
- Lipogenesis includes three main processes: glycerol synthesis, fatty acid synthesis, and triacylglycerol synthesis.
- Glycerol synthesis can be made from glycerol-3-phosphate, an intermediate product of glycolysis.
- Fatty acid synthesis uses acetyl-CoA and NADPH forming palmitic acid (16 carbon fatty acid). It happens in the cytosol of liver, mammary glands, and adipose tissue.
- Steps of Fatty acid synthesis: - Carboxylation of Acetyl-CoA to malonyl-CoA, needing acetyl-CoA carboxylase and ATP.
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Description
Explore the process of lipid digestion across different sites such as the mouth, stomach, and small intestine. This quiz covers key enzymes like lingual lipase, gastric lipase, and pancreatic lipase, detailing their roles in breaking down fats and cholesterol esters. Test your understanding of lipid metabolism!
