35 Questions
What is a clinical problem caused by a defect in the carnitine shuttle system?
Poor exercise tolerance
What is the byproduct of β-oxidation of fatty acids?
Acetyl-CoA
Where does the β-oxidation of fatty acids occur?
Mitochondria
What is required for the β-oxidation of fatty acids?
Oxygen
What is the end product of fatty acid synthesis?
Triacylglycerol
Where do fatty acids enter the cell?
Extracellular space
What is the first step in the degradation of fatty acids?
Activation of FAS
What is the vitamin contained in Coenzyme A?
Vitamin B5
What is the energy source required for the reaction of linking fatty acids to Coenzyme A?
ATP
What is the purpose of the carnitine shuttle system in fatty acid metabolism?
To regulate the rate of fatty acid oxidation
What is the molecule that inhibits the transport of activated fatty acids into mitochondria?
Malonyl-CoA
What is the product of the reaction between fatty acids and Coenzyme A?
Fatty acid-CoA
What is the enzyme that catalyzes the reaction between fatty acids and Coenzyme A?
Fatty acyl-CoA synthase
What is a characteristic of lipids?
They contain less O but more H
What is the function of triacylglycerols?
Fuel storage and insulation
What is the product of esterification of glycerol with three fatty acids?
Triacylglycerol
What is the breakdown of triacylglycerols known as?
Lipolysis
What is cholesterol used for in the body?
Membranes and steroid hormone synthesis
What type of compounds are vitamins A, D, E, and K?
Fatty acid derivatives
What is the class of lipids that includes bile acids and bile salts?
Hydroxy-methyl-glutaric acid derivatives
Where are triglycerides primarily stored in the body?
Adipose tissue
What hormones promote the storage of triglycerides?
Insulin
What is the primary function of triglycerides in the body?
To store energy for prolonged aerobic exercise and stress situations
What is the process by which dietary triglycerides are broken down?
Hydrolysis by pancreatic lipase
What is the fate of glycerol derived from the hydrolysis of dietary triglycerides?
It enters the bloodstream and is transported to the liver for metabolism
What is a characteristic property of fatty acids?
They are hydrophobic and highly reduced
Where does the lipogenesis pathway occur?
Cytoplasm
What is the source of acetyl-CoA in lipogenesis?
Carbohydrate and amino acid catabolism
What is the role of ATP in lipogenesis?
Energy source for the reaction
What is the role of NADPH in lipogenesis?
Reducing agent for the reaction
What is the source of NADPH in lipogenesis?
Pentose phosphate pathway
What is the enzyme that catalyzes the production of citrate from acetyl-CoA?
Citrate synthase
What is the role of citrate in the regulation of acetyl-CoA carboxylase?
Activator of the enzyme
What is the fate of excessive carbohydrate and protein consumed in excess of requirements?
Esterification to triacylglycerols
What is the effect of insulin on lipogenesis?
Activates the enzyme
Study Notes
Clinical Significance of Carnitine Shuttle
- Defects in the carnitine shuttle system can cause clinical problems, including poor exercise tolerance and high levels of triacylglycerols in muscle cells.
- This system is crucial for regulating the rate of fatty acid oxidation by controlling their entry into mitochondria.
Fatty Acid Oxidation
- Fatty acid oxidation occurs in the mitochondria, where fatty acids are broken down into acetyl-CoA.
- The oxidation process involves the removal of a C2 unit (acetate) from the fatty acid, which occurs repeatedly until only two carbon atoms remain.
- The overall reaction for the β-oxidation of stearic acid (C-18) is: C17H35COOH + 9 CoA + ATP + 8 FAD + 8 NAD+ + 8 H2O → 9 CH3CO-COA (acetyl-CoA) + AMP + 2 Pi + 8 FADH2 + 8 NADH + 8 H+
- β-oxidation of fatty acids requires mitochondrial NAD+ and FAD, and cannot occur in the absence of oxygen.
Fatty Acid Activation
- Fatty acid activation is the first step in fatty acid degradation, and involves linking fatty acids to coenzyme A (CoA).
- The reaction requires ATP and is catalyzed by fatty acyl CoA synthase.
- The activated fatty acid is then transported into the mitochondria for oxidation.
Lipid Metabolism
- Lipids are diverse and hydrophobic, containing CHO (and P and N in phospholipids).
- They are more reduced than carbohydrates and are present in the body in different forms.
- Classes of lipids include fatty acid derivatives, hydroxy-methyl-glutaric acid derivatives, and vitamins.
Triacylglycerols
- Triacylglycerols (TG) are the major dietary and storage lipid in the body.
- They consist of three fatty acids esterified to glycerol.
- TG are stored in adipose tissue and serve as a fuel source for prolonged aerobic exercise, stress situations, and during pregnancy.
Metabolism of TG
- Stage 1 of TG metabolism involves hydrolysis of dietary lipids by pancreatic lipase in the small intestine.
- Glycerol derived from TG hydrolysis is transported to the liver and metabolized.
- Triacylglycerol synthesis involves the reaction of glycerol and fatty acids.
Lipogenesis
- Fatty acids are synthesized from acetyl-CoA (derived from carbohydrate and amino acid catabolism) in the cytoplasm.
- The pathway requires ATP and NADPH and is regulated by allosteric regulation, insulin, and anti-insulin hormones.
- Excessive carbohydrate and protein consumption lead to esterification to triacylglycerols for storage in adipose tissue, which can cause obesity and associated problems.
This quiz covers the clinical significance of carnitine shuttle in the mitochondrial fatty acid transport system, its effects on exercise tolerance and fatty acid oxidation. Learn about the beta-oxidation of fatty acids and its process in the mitochondria.
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