Podcast
Questions and Answers
What is the enzyme responsible for converting triacylglycerols of chylomicrons into glycerol and free fatty acids?
What is the enzyme responsible for converting triacylglycerols of chylomicrons into glycerol and free fatty acids?
What process converts glycerol into glycerol-3-phosphate?
What process converts glycerol into glycerol-3-phosphate?
glycerolkinase
Tissue lipids, such as cholesterol and phospholipids, are oxidized to produce energy.
Tissue lipids, such as cholesterol and phospholipids, are oxidized to produce energy.
False
De Novo synthesis of fatty acids occurs in the _______________.
De Novo synthesis of fatty acids occurs in the _______________.
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Match the lipid fate with its corresponding process:
Match the lipid fate with its corresponding process:
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What is the enzyme responsible for the hydrolysis of triacylglycerols in adipose tissue?
What is the enzyme responsible for the hydrolysis of triacylglycerols in adipose tissue?
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What are the functions of glycerol and fatty acids after being acted upon by lipoprotein lipase?
What are the functions of glycerol and fatty acids after being acted upon by lipoprotein lipase?
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Citrate synthase frees CoA from acetyl CoA and condenses acetate and oxaloacetate to citrate.
Citrate synthase frees CoA from acetyl CoA and condenses acetate and oxaloacetate to citrate.
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The immediate donor of 2-carbon units in fatty acid synthesis is ________.
The immediate donor of 2-carbon units in fatty acid synthesis is ________.
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What is the main product of the cytoplasmic pathway of fatty acid synthesis?
What is the main product of the cytoplasmic pathway of fatty acid synthesis?
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Study Notes
Fate of Absorbed Lipids
- After a fatty meal, plasma appears milky due to excess chylomicrons in venous blood, which stimulates mast cells to produce heparin.
- Heparin stimulates the lining epithelium of blood vessels to produce lipoprotein lipase (plasma clearing factor).
- Lipoprotein lipase acts on triacylglycerols of chylomicrons, converting them into glycerol and free fatty acids.
Fate of Glycerol and Fatty Acids
- Glycerol and fatty acids are taken up by different tissues for various functions:
- Formation of depot fat (mainly triacylglycerols in adipose tissue)
- Oxidation for energy production (fatty acids converted to acetyl CoA and glycerol to dihydroxyacetone phosphate)
- Glucose formation by gluconeogenesis (glycerol → glucose, odd-numbered fatty acid oxidation → propionyl CoA → glucose)
- Synthesis of biologically active compounds (e.g., steroids)
- Synthesis of tissue fats (structural fats, e.g., phospholipids and cholesteryl ester)
Body Lipids
- Two types of lipids: tissue lipids (constant element) and adipose tissue (depot fat, variable element)
- Tissue lipids: enter the structure of body cells (e.g., cell membrane, mitochondria), mainly cholesterol, phospholipids, and some triacylglycerols; never oxidized to give energy
- Adipose tissue:
- White adipose tissue (energy): present under skin, composed of triacylglycerols; provides energy during fasting
- Brown adipose tissue (heat): certain areas of adipose tissue, contains high amounts of mitochondria
Lipogenesis and Lipolysis
- Lipogenesis: synthesis of triacylglycerol from fatty acids and glycerol
- Activation of fatty acids
- Synthesis of glycerol-3-phosphate
- Esterification
- Lipolysis: hydrolysis of triacylglycerols in adipose tissue into glycerol and fatty acids
- Steps: hormone-sensitive lipase enzymes, diacylglycerol lipase, and monoacylglycerol lipase
Regulation of Lipogenesis and Lipolysis
- In the fed state: increased lipogenesis, insulin/glucagon ratio stimulates lipoprotein lipase, increasing fatty acid uptake in adipose cells
- In the fasting state: increased lipolysis, insulin/glucagon ratio decrease, and hormone-sensitive lipase enzyme is activated
De Novo Fatty Acid Synthesis
- Occurs in cytoplasm of liver, adipose tissue, mammary gland, lung, and kidney
- Requirements: acetyl CoA, NADPH+H, and fatty acid synthase complex
- Steps: A. Carboxylation of acetyl CoA to malonyl CoA B. Transport of acetyl-CoA to the site 1 of ACP C. Transport of malonyl-CoA to the site 2 ACP D. Synthesis of palmitate
- Fates of palmitate: esterification, chain elongation, and desaturation
Regulation of De Novo Fatty Acid Synthesis
- Allosteric regulation: citrate stimulates acetyl-CoA carboxylase, while long-chain fatty acids and palmitate inhibit it
- Covalent modification: insulin increases the dephosphorylated form, stimulating FA synthesis, while glucagon and epinephrine increase the phosphorylated form, inhibiting FA synthesis
Fate of Absorbed Lipids
- After a fatty meal, plasma appears milky due to excess chylomicrons in venous blood, which stimulates mast cells to produce heparin.
- Heparin stimulates the lining epithelium of blood vessels to produce lipoprotein lipase (plasma clearing factor).
- Lipoprotein lipase acts on triacylglycerols of chylomicrons, converting them into glycerol and free fatty acids.
Fate of Glycerol and Fatty Acids
- Glycerol and fatty acids are taken up by different tissues for various functions:
- Formation of depot fat (mainly triacylglycerols in adipose tissue)
- Oxidation for energy production (fatty acids converted to acetyl CoA and glycerol to dihydroxyacetone phosphate)
- Glucose formation by gluconeogenesis (glycerol → glucose, odd-numbered fatty acid oxidation → propionyl CoA → glucose)
- Synthesis of biologically active compounds (e.g., steroids)
- Synthesis of tissue fats (structural fats, e.g., phospholipids and cholesteryl ester)
Body Lipids
- Two types of lipids: tissue lipids (constant element) and adipose tissue (depot fat, variable element)
- Tissue lipids: enter the structure of body cells (e.g., cell membrane, mitochondria), mainly cholesterol, phospholipids, and some triacylglycerols; never oxidized to give energy
- Adipose tissue:
- White adipose tissue (energy): present under skin, composed of triacylglycerols; provides energy during fasting
- Brown adipose tissue (heat): certain areas of adipose tissue, contains high amounts of mitochondria
Lipogenesis and Lipolysis
- Lipogenesis: synthesis of triacylglycerol from fatty acids and glycerol
- Activation of fatty acids
- Synthesis of glycerol-3-phosphate
- Esterification
- Lipolysis: hydrolysis of triacylglycerols in adipose tissue into glycerol and fatty acids
- Steps: hormone-sensitive lipase enzymes, diacylglycerol lipase, and monoacylglycerol lipase
Regulation of Lipogenesis and Lipolysis
- In the fed state: increased lipogenesis, insulin/glucagon ratio stimulates lipoprotein lipase, increasing fatty acid uptake in adipose cells
- In the fasting state: increased lipolysis, insulin/glucagon ratio decrease, and hormone-sensitive lipase enzyme is activated
De Novo Fatty Acid Synthesis
- Occurs in cytoplasm of liver, adipose tissue, mammary gland, lung, and kidney
- Requirements: acetyl CoA, NADPH+H, and fatty acid synthase complex
- Steps: A. Carboxylation of acetyl CoA to malonyl CoA B. Transport of acetyl-CoA to the site 1 of ACP C. Transport of malonyl-CoA to the site 2 ACP D. Synthesis of palmitate
- Fates of palmitate: esterification, chain elongation, and desaturation
Regulation of De Novo Fatty Acid Synthesis
- Allosteric regulation: citrate stimulates acetyl-CoA carboxylase, while long-chain fatty acids and palmitate inhibit it
- Covalent modification: insulin increases the dephosphorylated form, stimulating FA synthesis, while glucagon and epinephrine increase the phosphorylated form, inhibiting FA synthesis
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Description
This quiz covers the fate of absorbed lipids, including the role of chylomicrons, lipoprotein lipase, and heparin in lipid metabolism. Learn about the process of lipid absorption and how it affects the plasma.
