Multiple Choice
Rank the following molecules based on amount of energy stored in them in increasing order (per mol).
I. Sucrose II. Arachidic III. Glucose IV. Behenic (22:0)
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24. Lipid Metabolism
Total Energy from Fatty Acids
1:23 minutesProblem 49a
Textbook Question
How many molecules of acetyl-CoA result from complete catabolism of the following compounds?
a. Myristic acid, CH3(CH2)12COOH
Verified step by step guidance1
Identify the structure of myristic acid: Myristic acid is a saturated fatty acid with the formula CH₃(CH₂)₁₂COOH. It contains 14 carbon atoms in total (1 from CH₃, 12 from CH₂ groups, and 1 from the carboxylic acid group).
Understand the process of beta-oxidation: Beta-oxidation is the metabolic pathway that breaks down fatty acids into acetyl-CoA molecules. Each cycle of beta-oxidation removes a 2-carbon unit (as acetyl-CoA) from the fatty acid chain.
Determine the number of beta-oxidation cycles: Since myristic acid has 14 carbon atoms, divide the total number of carbons by 2 to determine the number of acetyl-CoA molecules produced. This gives 14 ÷ 2 = 7 acetyl-CoA molecules.
Account for the number of beta-oxidation cycles: The number of beta-oxidation cycles required to completely break down the fatty acid is one less than the number of acetyl-CoA molecules produced. For myristic acid, this would be 7 - 1 = 6 cycles.
Summarize the result: The complete catabolism of myristic acid through beta-oxidation produces 7 molecules of acetyl-CoA. Each acetyl-CoA can then enter the citric acid cycle for further energy production.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Beta-Oxidation
Beta-oxidation is the metabolic process by which fatty acids are broken down in the mitochondria to generate acetyl-CoA. Each cycle of beta-oxidation shortens the fatty acid chain by two carbon atoms, producing one molecule of acetyl-CoA, along with NADH and FADH2, which are used in the electron transport chain for ATP production.
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Fatty Acid Structure
Fatty acids are long hydrocarbon chains with a carboxylic acid group at one end. The number of carbon atoms in the fatty acid determines how many cycles of beta-oxidation will occur. For example, myristic acid has 14 carbon atoms, which influences the total number of acetyl-CoA molecules produced during its complete catabolism.
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Acetyl-CoA Production
Acetyl-CoA is a key metabolic intermediate that enters the citric acid cycle (Krebs cycle) for energy production. Each complete cycle of beta-oxidation of a fatty acid yields one acetyl-CoA molecule, and the total number of acetyl-CoA molecules produced can be calculated by dividing the total number of carbon atoms in the fatty acid by two.
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