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Ch.12 Food as Fuel An Overview of Metabolism
Frost - General, Organic and Biological Chemistry 4th Edition
Frost4th EditionGeneral, Organic and Biological ChemistryISBN: 9780134988696Not the one you use?Change textbook
All textbooksFrost 4th EditionCh.12 Food as Fuel An Overview of MetabolismProblem 94b
Chapter 8, Problem 94b

Consider the complete oxidation of arachidic acid, a saturated fatty acid, [20:0].
b. How many cycles of β oxidation occur?

Verified step by step guidance
1
Step 1: Understand the structure of arachidic acid. Arachidic acid is a saturated fatty acid with the formula C20H40O2, indicating it has 20 carbon atoms and no double bonds.
Step 2: Recall the process of β oxidation. In β oxidation, each cycle removes a two-carbon unit (acetyl-CoA) from the fatty acid chain. The number of cycles required is determined by the number of two-carbon units that can be removed.
Step 3: Determine the number of acetyl-CoA molecules produced. For a fatty acid with n carbons, the number of acetyl-CoA molecules produced is n/2. Since arachidic acid has 20 carbons, it will produce 20/2 = 10 acetyl-CoA molecules.
Step 4: Calculate the number of β oxidation cycles. The number of cycles is one less than the number of acetyl-CoA molecules produced because the final two-carbon unit does not require a cycle to be removed. Therefore, the number of cycles is 10 - 1 = 9.
Step 5: Conclude that the complete oxidation of arachidic acid involves 9 cycles of β oxidation. This is based on the systematic removal of two-carbon units until the fatty acid is fully oxidized.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

β-Oxidation

β-Oxidation is a metabolic process that breaks down fatty acids into acetyl-CoA units, which can then enter the citric acid cycle for energy production. Each cycle of β-oxidation removes two carbon atoms from the fatty acid chain, producing one molecule of acetyl-CoA and reducing equivalents in the form of NADH and FADH2.

Fatty Acid Structure

Fatty acids are long hydrocarbon chains with a carboxylic acid group at one end. Arachidic acid, specifically, is a saturated fatty acid with 20 carbon atoms. Understanding the structure of fatty acids is crucial for determining how many cycles of β-oxidation will occur, as the number of cycles is directly related to the length of the carbon chain.
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Fatty Acids Example 1

Cycle Calculation

The number of β-oxidation cycles can be calculated using the formula: (n/2) - 1, where n is the total number of carbon atoms in the fatty acid. For arachidic acid (20 carbons), this means (20/2) - 1 = 9 cycles of β-oxidation will occur, leading to the complete oxidation of the fatty acid.
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The Urea Cycle Concept 3
Related Practice
Textbook Question

In what organ does the urea cycle take place?

Textbook Question

Lauric acid, a saturated fatty acid, [12:0], is found in coconut oil.

a. Draw fatty acyl lauric acid activated for β oxidation.

Textbook Question

What metabolic substrate(s) can be produced from the carbon atoms of each of the following amino acids?

c. methionine

Textbook Question

Lauric acid, a saturated fatty acid, [12:0], is found in coconut oil.

e. How many cycles of β oxidation occur?

Textbook Question

A person is brought to the emergency room in what appears to be a drunken stupor. On closer examination, she seems to be breathing very rapidly and you notice a sweet-smelling odor on her breath. You find out this person has not been drinking alcohol. What is her likely condition?

Textbook Question

Consider the complete oxidation of capric acid, a saturated fatty acid, [10:0].

c How many ATP are generated from the complete oxidation of capric acid?