Questions and Answers
What are the major forms of energy involved in the digestion, absorption, and transportation of lipids?
What character do bile acids have that helps in the solubilization and absorption of lipids in the gut?
Detergent character
Lipids are absorbed as micelles with bile salts and _______ or as lipid-protein complexes.
lecithin
Fatty acids can be incorporated into either storage triacylglycerols or phospholipid components of membranes.
Signup and view all the answers
Match the following stages of lipid metabolism with their descriptions:
Signup and view all the answers
What is the major form of energy mentioned in the content related to the metabolism of macromolecules?
Signup and view all the answers
How are lipids absorbed by enterocytes?
Signup and view all the answers
______ is the process by which stored fat in adipose tissue is broken down into free fatty acids and glycerol.
Signup and view all the answers
Ketone bodies are primarily synthesized in the brain.
Signup and view all the answers
Study Notes
Digestion, Absorption, and Transportation of Lipids
- Triacylglycerols (triglycerides) are the major form of energy, making up 90% of dietary lipids
- They provide 6 times more energy per unit weight than glycogen
- Triacylglycerols are water-insoluble and require emulsification by bile salts and bile acids in the small intestine for digestion
- Bile acids have a detergent character, helping to solubilize and absorb lipids in the gut
- Lipid absorption occurs in enterocytes as micelles with bile salts and lecithin or as lipid-protein complexes
- Lipids are transported as lipoproteins, which are lipid-protein complexes that make lipids soluble
Lipid Metabolism
- Lipid metabolism involves the breakdown of fats (lipids) for energy and storage
- The process involves multiple steps and enzymes that are tightly regulated
- Biosynthesis of triacylglycerols (lipogenesis) involves the incorporation of fatty acids into triacylglycerols for storage or into phospholipid components of membranes
- Triacylglycerols and glycerophospholipids share two precursors: fatty acyl-CoA and L-glycerol 3-phosphate
- The majority of glycerol 3-phosphate is derived from dihydroxyacetone phosphate (DHAP) by the action of cytosolic NAD-linked glycerol 3-phosphate dehydrogenase
- Fatty acyl-CoAs are formed from fatty acids by acyl-CoA synthetases, the same enzymes responsible for the activation of fatty acids for β-oxidation
Biosynthesis of Triacylglycerols
- The first stage in biosynthesis is the acylation of the two free hydroxyl groups of L-glycerol 3-phosphate by two molecules of fatty acyl-CoA to yield diacylglycerol 3-phosphate (phosphatidic acid)
- Phosphatidic acid is a central intermediate in lipid biosynthesis and can be converted to a triacylglycerol or a glycerophospholipid
- In the pathway to triacylglycerols, phosphatidic acid is hydrolyzed by phosphatidic acid phosphatase (lipin) to form a 1,2-diacylglycerol
- Diacylglycerols are then converted to triacylglycerols by transesterification with a third fatty acyl-CoA
Lipolysis
- Lipolysis is the process by which stored fat in adipose tissue is broken down into free fatty acids and glycerol
- This process is regulated by hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL)
- Fatty acids are mobilized from triacylglycerols and oxidized to meet the energy needs of the cell or organism
Fatty Acid Oxidation
- Fatty acid oxidation involves the breakdown of fatty acids into acetyl-CoA, which is then processed in the citric acid cycle
- The process of degradation converts an aliphatic compound into a set of activated acetyl units (acetyl-CoA) that can be processed by the citric acid cycle
- The repetitive four-step process by which fatty acids are converted into acetyl-CoA is called β-oxidation
- Triacylglycerols are highly concentrated stores of metabolic energy because they are reduced and anhydrous
Ketone Bodies
- Ketogenesis occurs when excess fatty acids are converted into ketone bodies, such as acetoacetate, β-hydroxybutyrate, and acetone
- This process occurs in the liver and is regulated by enzymes such as β-ketoacyl-CoA transferase and β-hydroxybutyrate dehydrogenase
- Ketone bodies are produced when the supply of carbohydrates is low and the body needs to use fat as its primary fuel source
- Acetoacetate and D-β-hydroxybutyrate are transported by the blood to tissues other than the liver, where they are converted to acetyl-CoA and oxidized in the citric acid cycle
Digestion, Absorption, and Transportation of Lipids
- Triacylglycerols (triglycerides) are the major form of energy, making up 90% of dietary lipids
- They provide 6 times more energy per unit weight than glycogen
- Triacylglycerols are water-insoluble and require emulsification by bile salts and bile acids in the small intestine for digestion
- Bile acids have a detergent character, helping to solubilize and absorb lipids in the gut
- Lipid absorption occurs in enterocytes as micelles with bile salts and lecithin or as lipid-protein complexes
- Lipids are transported as lipoproteins, which are lipid-protein complexes that make lipids soluble
Lipid Metabolism
- Lipid metabolism involves the breakdown of fats (lipids) for energy and storage
- The process involves multiple steps and enzymes that are tightly regulated
- Biosynthesis of triacylglycerols (lipogenesis) involves the incorporation of fatty acids into triacylglycerols for storage or into phospholipid components of membranes
- Triacylglycerols and glycerophospholipids share two precursors: fatty acyl-CoA and L-glycerol 3-phosphate
- The majority of glycerol 3-phosphate is derived from dihydroxyacetone phosphate (DHAP) by the action of cytosolic NAD-linked glycerol 3-phosphate dehydrogenase
- Fatty acyl-CoAs are formed from fatty acids by acyl-CoA synthetases, the same enzymes responsible for the activation of fatty acids for β-oxidation
Biosynthesis of Triacylglycerols
- The first stage in biosynthesis is the acylation of the two free hydroxyl groups of L-glycerol 3-phosphate by two molecules of fatty acyl-CoA to yield diacylglycerol 3-phosphate (phosphatidic acid)
- Phosphatidic acid is a central intermediate in lipid biosynthesis and can be converted to a triacylglycerol or a glycerophospholipid
- In the pathway to triacylglycerols, phosphatidic acid is hydrolyzed by phosphatidic acid phosphatase (lipin) to form a 1,2-diacylglycerol
- Diacylglycerols are then converted to triacylglycerols by transesterification with a third fatty acyl-CoA
Lipolysis
- Lipolysis is the process by which stored fat in adipose tissue is broken down into free fatty acids and glycerol
- This process is regulated by hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL)
- Fatty acids are mobilized from triacylglycerols and oxidized to meet the energy needs of the cell or organism
Fatty Acid Oxidation
- Fatty acid oxidation involves the breakdown of fatty acids into acetyl-CoA, which is then processed in the citric acid cycle
- The process of degradation converts an aliphatic compound into a set of activated acetyl units (acetyl-CoA) that can be processed by the citric acid cycle
- The repetitive four-step process by which fatty acids are converted into acetyl-CoA is called β-oxidation
- Triacylglycerols are highly concentrated stores of metabolic energy because they are reduced and anhydrous
Ketone Bodies
- Ketogenesis occurs when excess fatty acids are converted into ketone bodies, such as acetoacetate, β-hydroxybutyrate, and acetone
- This process occurs in the liver and is regulated by enzymes such as β-ketoacyl-CoA transferase and β-hydroxybutyrate dehydrogenase
- Ketone bodies are produced when the supply of carbohydrates is low and the body needs to use fat as its primary fuel source
- Acetoacetate and D-β-hydroxybutyrate are transported by the blood to tissues other than the liver, where they are converted to acetyl-CoA and oxidized in the citric acid cycle
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the metabolism of macromolecules, specifically the digestion, absorption, and transportation of lipids, including their energy content and solubility.