26 Questions
What is the net energy yield from the oxidation of one molecule of palmitoyl CoA to CO2 and H2O?
129 ATP
What is the role of flavin adenine dinucleotide (FAD) in β-oxidation?
To accept electrons during the β-oxidation of fatty acids
What is the name of the enzyme that is deficient in medium-chain fatty acyl CoA dehydrogenase deficiency?
Medium-chain fatty acyl CoA dehydrogenase
During β-oxidation, how many molecules of acetyl CoA are produced from one molecule of palmitoyl CoA?
8
What is the energy cost of activating a fatty acid for β-oxidation?
2 ATP
How many molecules of NADH are produced during the β-oxidation of one molecule of palmitoyl CoA?
7
What is the name of the coenzyme that is reduced during the β-oxidation of fatty acids?
FAD
What is the product of the β-oxidation of palmitoyl CoA?
CO2 and H2O
How many ATP molecules are generated when one acetyl-CoA is converted to CO2 and H2O by the TCA cycle?
12
What is the number of FADH2 molecules generated in the β-oxidation of one palmitoyl-CoA molecule?
7
What is the total ATP yield from the complete oxidation of one palmitoyl-CoA molecule?
129
How many NADH molecules are generated when one palmitoyl-CoA molecule is β-oxidized to acetyl-CoA?
14
What is the ATP yield when one FADH2 is oxidized by the electron transport chain?
3
How many carbon atoms are present in the intermediate C10-CoA?
10
What is the byproduct of the TCA cycle when acetyl-CoA is converted to CO2 and H2O?
H2O
How many ATP molecules are generated when one NADH is oxidized by the electron transport chain?
3
What is the intermediate molecule formed when C2-CoA is converted to acetyl-CoA?
Acetyl-CoA
How many ATP molecules are generated when one FADH2 is oxidized by the electron transport chain and the TCA cycle?
12
What is the primary function of the CPT system in mitochondria?
To oxidize long-chain fatty acids
What is the result of the first cycle of β-oxidation?
Shortening of the fatty acid chain by two carbons
Which of the following is a characteristic of medium-chain fatty acids?
They are plentiful in human milk
What is the role of 3-hydroxyacyl CoA dehydrogenase in β-oxidation?
To reduce NAD+ to NADH
Which of the following is NOT a step in the β-oxidation reaction?
Synthesis of ATP
What is the purpose of the four reactions in the β-oxidation cycle?
To shorten the fatty acid chain by two carbons
What is the effect of malonyl CoA on medium-chain fatty acid oxidation?
It has no effect on the oxidation of medium-chain fatty acids
What is the role of matrix enzymes in β-oxidation?
To activate medium-chain fatty acids to their CoA derivatives
Study Notes
Energy Yield from Fatty Acid Oxidation
- The energy yield from the trans double bond between carbon 2 and carbon 3 in the β-oxidation pathway is high.
- The oxidation of a molecule of palmitoyl CoA to CO2 and H2O produces 8 acetyl CoA, 7 NADH, and 7 FADH2, from which 131 ATP can be generated.
- However, the activation of the fatty acid requires 2 ATP, so the net yield from palmitate is 129 ATP.
Medium-Chain Fatty Acyl CoA Dehydrogenase Deficiency
- In mitochondria, there are four fatty acyl CoA dehydrogenase species, each with distinct but overlapping specificity for either short-, medium-, long-, or VLCFAs.
- Medium-chain fatty acyl CoA dehydrogenase deficiency can be compensated by other dehydrogenases.
Mobilization of Stored Fats and Oxidation of Fatty Acids
- The number of carbons contained in the intermediates of β-oxidation determines the energy yield.
- Each acetyl CoA produced during β-oxidation yields 12 ATP when converted to CO2 and H2O by the TCA cycle.
- FADH2 and NADH produced during β-oxidation yield 2 ATP and 3 ATP, respectively, when oxidized by the electron transport chain.
Entry of Short- and Medium-Chain Fatty Acids into the Mitochondria
- Fatty acids shorter than 12 carbons can cross the inner mitochondrial membrane without the aid of carnitine or the CPT system.
- Once inside the mitochondria, they are activated to their CoA derivatives by matrix enzymes and are oxidized.
Reactions of β-Oxidation
- The first cycle of β-oxidation involves a sequence of four reactions involving the β-carbon (carbon 3) that results in shortening the fatty acid chain by two carbons at the carboxylate end.
- The oxidation of medium-chain fatty acids is not dependent on CPT-I and is not subject to inhibition by malonyl CoA.
Calculation of energy yield from fatty acid oxidation, including the β-oxidation pathway and ATP generation. Also covers Medium-Chain Fatty Acyl CoA Dehydrogenase Deficiency.
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