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Ch. 24 Nutrition, Metabolism, and Energy Balance
Marieb - Human Anatomy & Physiology 11th Edition
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Not the one you use?Change textbook
All textbooksMarieb, Hoehn 11th EditionCh. 24 Nutrition, Metabolism, and Energy BalanceProblem 21
Chapter 24, Problem 21

Calculate the number of ATP molecules that can be harvested during the complete oxidation of an 18-carbon fatty acid.

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Step 1: Understand the process of fatty acid oxidation. Fatty acids are broken down through beta-oxidation, which occurs in the mitochondria. Each cycle of beta-oxidation removes two carbons from the fatty acid chain, producing acetyl-CoA, NADH, and FADH2.
Step 2: Determine the number of beta-oxidation cycles required for an 18-carbon fatty acid. Since each cycle removes two carbons, divide the total number of carbons (18) by 2 to find the number of acetyl-CoA molecules produced. Subtract 1 from this number to find the number of beta-oxidation cycles.
Step 3: Calculate the ATP yield from beta-oxidation. Each beta-oxidation cycle produces 1 NADH and 1 FADH2. Use the following approximate ATP yields: 1 NADH = 2.5 ATP and 1 FADH2 = 1.5 ATP. Multiply the number of beta-oxidation cycles by these values to find the total ATP from NADH and FADH2.
Step 4: Calculate the ATP yield from acetyl-CoA. Each acetyl-CoA enters the citric acid cycle (Krebs cycle), producing 3 NADH, 1 FADH2, and 1 GTP (equivalent to 1 ATP). Multiply the number of acetyl-CoA molecules by these values to find the total ATP from the citric acid cycle.
Step 5: Account for the energy cost of fatty acid activation. Before beta-oxidation begins, the fatty acid must be activated, which requires 2 ATP molecules. Subtract this energy cost from the total ATP yield calculated in the previous steps to find the net ATP 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, which then enters the citric acid cycle for further energy extraction.
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Fatty Acid Oxidation 2

Citric Acid Cycle (Krebs Cycle)

The citric acid cycle is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA. Each turn of the cycle produces ATP, NADH, and FADH2, which are crucial for the electron transport chain, ultimately leading to the production of additional ATP.
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Krebs Cycle

Electron Transport Chain (ETC)

The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient. This gradient drives ATP synthesis through ATP synthase, yielding a significant amount of ATP from the oxidation of fatty acids and other substrates.
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Electron Transport Chain
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