B-Oxidation/FA Catabolism Flashcards
Which organs are involved in lipid digestion?
Stomach and small intestine.
What is the main function of triacylglycerol metabolism?
Synthesis and degradation of triacylglycerols.
How much ATP is produced from β-oxidation of one palmitoyl CoA (16 carbons)?
129 ATP
How much ATP is produced from glycolysis of one glucose (6 carbons)?
38 ATP
What is the precursor for de novo synthesis of fatty acids and cholesterol?
Acetyl-CoA
What compound extends fatty acids during synthesis?
Malonyl-CoA
What is the structural basis for steroid-based hormones and biomolecules?
Cholesterol
What are the main products of β-oxidation?
Acetyl-CoA, NADH, and QH2
Where does β-oxidation occur in eukaryotic cells?
In the mitochondria and peroxisomes.
What type of reaction initiates β-oxidation?
Oxidation of the acyl group.
What is the fourth step of β-oxidation?
Thiolysis and the release of acetyl-CoA.
Which cofactor is required for the first oxidation step?
FAD (Flavin adenine dinucleotide).
What type of reaction is the thiolysis step similar to?
Retro-Claisen condensation.
What is produced after one cycle of β-oxidation?
Acetyl-CoA and an (n-2)-acyl-CoA.
What is the nucleophile in the thiolysis step?
HS-CoA (Coenzyme A).
How many steps are involved in each cycle of β-oxidation?
Four steps.
What happens to the shortened acyl-CoA after one cycle?
It re-enters the β-oxidation cycle.
Why is β-oxidation crucial for energy production?
It provides acetyl-CoA for the citric acid cycle and NADH/QH2 for the electron transport chain.
What happens if there is a defect in β-oxidation?
It can lead to energy deficiencies and accumulation of fatty acids.
Why is FAD used in the first oxidation instead of NAD+?
FAD is better suited for oxidizing saturated carbon-carbon bonds.
Which tissues rely heavily on β-oxidation for energy?
Heart and skeletal muscle.
How is β-oxidation regulated?
By the availability of fatty acids, malonyl-CoA levels, and energy demands.
What is the first step of fatty acid catabolism, and what enzyme is involved?
The first step is the oxidation of Acyl CoA by the enzymeacyl CoA dehydrogenase, producingtrans-2-enoyl CoA,FADH₂, andQH₂. This step produces2 ATP.
What happens in the second step of fatty acid catabolism?
In the second step,trans-2-enoyl CoAis hydrolyzed by the enzyme2-enoyl-CoA hydratasewithH₂Oto produceL-3-hydroxyacyl CoA.
What is the third step of fatty acid catabolism, and what is produced?
The third step involves the oxidation ofL-3-hydroxyacyl CoAby the enzyme3-hydroxyacyl CoA dehydrogenasewithNAD⁺, producing3-ketoacyl CoA,NADH, andH⁺. This step produces3 ATP.
What occurs in the fourth step of fatty acid catabolism?
In the fourth step,3-ketoacyl CoAundergoes thiolysis by the enzyme3-ketoacyl-CoA thiolasewithHS-CoA, producingacyl CoAandacetyl CoA. This step produces12 ATPvia the TCA cycle.
Where does β-oxidation of long-chain fatty acids occur in eukaryotes?
β-oxidation of long-chain fatty acids primarily occurs in themitochondria. Very-long-chain fatty acids (≥ 22 carbons) begin β-oxidation in theperoxisomes.
What is the role of peroxisomes in fatty acid catabolism?
Peroxisomes are specialized for breaking downvery-long-chain fatty acids (≥ 22 carbons)andbranched fatty acids. They generateacetyl-CoAandhydrogen peroxide (H₂O₂)instead of FADH₂ for energy.
What are the products of β-oxidation in mitochondria?
The products areacetyl-CoA,NADH, andFADH₂. These enter thecitric acid cycleandelectron transport chainfor ATP generation.
What is the key distinction between mitochondria and peroxisomes?
Mitochondria: Major site for energy production from Fas. Peroxisomes: Specialized for breaking down very-long chains of Fas and branched FAs.
How mnay ATP molecules are produced from the B-oxidation of palmitoyl-CoA?
7 FADH2 x 2ATP = 14 ATP; 7 NADH x 3 ATP = 21 ATP; 8 acetyl-CoA x 12 ATP = 96 ATP; Total ATP = 131 ATP; Net ATP (after subtracting 2 ATP for activation ) = 129 ATP
