Questions and Answers
Which of the following statements accurately describes the oxidation of unsaturated fatty acids compared to saturated fatty acids?
What is the primary site of fatty acid oxidation?
Which type of oxidation yields acetyl CoA from fatty acids?
Which organ does not perform β-oxidation?
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What role does carnitine play in fatty acid oxidation?
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What is produced when fatty acids undergo β-oxidation?
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Which enzyme is responsible for the activation of fatty acids in the cytosol?
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How many ATP are consumed during the activation of fatty acids?
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What happens to the length of the fatty acyl CoA during β-oxidation?
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What is the net yield of ATP from the β-oxidation of palmitic acid?
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How many molecules of acetyl-CoA are produced from the β-oxidation of a 16-carbon fatty acid?
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What is the role of FAD in the first step of β-oxidation?
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Which of the following statements about β-oxidation is NOT true?
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How many β-oxidation cycles are required to completely break down a 14-carbon fatty acid?
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What is the purpose of the hydration step in β-oxidation?
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What is the net yield of ATP from the oxidation of one molecule of FADH2 in the electron transport chain?
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What is the primary function of β-oxidation?
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Study Notes
Fatty Acid Oxidation
- Fatty acid oxidation is a major source of cell ATP.
- It occurs in two pathways: major (β-oxidation) and minor (α- and ω-oxidation).
β-Oxidation Pathway
- Site: mitochondria (where enzymes for fatty acid oxidation are present close to the electron transport chain).
- Organ location: liver, kidney, heart, and skeletal muscles (but not brain, as fatty acids can't pass the blood-brain barrier and RBCs lack mitochondria).
- Steps of β-oxidation:
- Activation of fatty acids in the cytosol by thiokinase (2 ATP).
- Transport of acyl-CoA from cytosol into mitochondria by Carnitine Shuttle.
- β-oxidation has 4 steps: dehydrogenation (FAD-dependent), hydration, dehydrogenation (NAD-dependent), and cleavage (remove 2C as acetyl CoA).
- Calculations:
- Number of β-oxidation cycles = (C/2) - 1.
- Number of acetyl CoA molecules = C/2.
Energy Yield of Palmitoyl-CoA Oxidation
- Number of cycles = 7.
- Number of acetyl CoA molecules = 8.
- Total energy yield: 21 ATP (from NADH) + 14 ATP (from FADH2) + 96 ATP (from TCA cycle) = 131 ATP.
- Net energy yield: 129 ATP (after subtracting 2 ATP used in activation).
Importance of β-Oxidation
- Energy production (e.g., palmitic acid produces 129 ATP).
- Production of acetyl CoA (which enters many pathways).
- Ketone bodies formation (acetoacetyl CoA is converted into acetoacetate).
Oxidation of Unsaturated Fatty Acids
- Slightly more complicated and requires additional enzymes.
- Produces less energy than saturated fatty acids (due to being less highly reduced).
Oxidation of Odd-Numbered Fatty Acids
- Requires three additional reactions.
- Present in plants and marine organisms.
- Fatty acids with odd number of carbon atoms are oxidized by β-oxidation, producing acetyl-CoA and propionyl-CoA (3C) in the final round.
α-Oxidation Pathway
- Occurs in α-position and is characterized by:
- Mainly for oxidation of branched chain fatty acids (methylated at β-position).
- Specific for oxidation of Phytanic acid (present in plant foodstuffs).
- Minor pathway for fatty acid oxidation, occurring mainly in brain and nervous tissues.
- In α-oxidation, one carbon atom is removed at a time from the α position, without requiring CoASH and generating high energy phosphate.
Refsum's Disease
- Inherited deficiency of enzymes responsible for α-oxidation of Phytanic acid.
- Manifestation: accumulation of Phytanic acid in nervous tissue, causing nervous damage (e.g., deafness and blindness).
ω-Oxidation Pathway
- Minor pathway occurring in the endoplasmic reticulum of many tissues (not mitochondria).
- ω-oxidation occurs in the endoplasmic reticulum rather than mitochondria.
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Description
Learn about fatty acid oxidation, a major source of cell ATP, including β-oxidation, α-oxidation, and ω-oxidation pathways.
