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Questions and Answers
What is the primary form in which newly synthesized fatty acids are found in cells?
What is the primary form in which newly synthesized fatty acids are found in cells?
Which substrate is directly converted to malonyl-CoA in the fatty acid biosynthesis pathway?
Which substrate is directly converted to malonyl-CoA in the fatty acid biosynthesis pathway?
What is the primary enzymatic complex responsible for the elongation of the hydrocarbon chain during fatty acid biosynthesis?
What is the primary enzymatic complex responsible for the elongation of the hydrocarbon chain during fatty acid biosynthesis?
How do the concentrations of free fatty acids in most cells compare to acyl-CoA esters?
How do the concentrations of free fatty acids in most cells compare to acyl-CoA esters?
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Which of the following statements regarding fatty acid metabolism is incorrect?
Which of the following statements regarding fatty acid metabolism is incorrect?
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What triggers the addition of two-carbon units during fatty acid biosynthesis?
What triggers the addition of two-carbon units during fatty acid biosynthesis?
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What is the role of biotin in the process of fatty acid biosynthesis?
What is the role of biotin in the process of fatty acid biosynthesis?
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Which enzyme is responsible for the carboxylation of acetyl-CoA to form Malonyl-CoA?
Which enzyme is responsible for the carboxylation of acetyl-CoA to form Malonyl-CoA?
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What is the product of the condensation reaction that involves Acetyl-CoA and Malonyl-CoA?
What is the product of the condensation reaction that involves Acetyl-CoA and Malonyl-CoA?
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What occurs immediately after the reduction of the beta-carbonyl group in fatty acid biosynthesis?
What occurs immediately after the reduction of the beta-carbonyl group in fatty acid biosynthesis?
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What is the primary substrate from which most dietary fats are derived?
What is the primary substrate from which most dietary fats are derived?
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What triggers the release of fatty acids from adipose tissue?
What triggers the release of fatty acids from adipose tissue?
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Which enzyme is responsible for hydrolyzing triacylglycerols?
Which enzyme is responsible for hydrolyzing triacylglycerols?
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In which cellular organelle does fatty acid degradation primarily occur?
In which cellular organelle does fatty acid degradation primarily occur?
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What is the initial step in the β oxidation process of fatty acids?
What is the initial step in the β oxidation process of fatty acids?
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Which of the following statements about energy yield is correct?
Which of the following statements about energy yield is correct?
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Which type of fatty acid has a less efficient energy yield due to its structure?
Which type of fatty acid has a less efficient energy yield due to its structure?
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Which of the following enzymes catalyzes the hydrolysis of phosphoacylglycerols?
Which of the following enzymes catalyzes the hydrolysis of phosphoacylglycerols?
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What is the total ATP yield from one molecule of palmitic acid (16 C) after fatty acid oxidation?
What is the total ATP yield from one molecule of palmitic acid (16 C) after fatty acid oxidation?
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What is necessary for the oxidation of unsaturated fatty acids?
What is necessary for the oxidation of unsaturated fatty acids?
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How many kcal does a 200 g bird need per day when relying on fat as energy?
How many kcal does a 200 g bird need per day when relying on fat as energy?
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Which enzyme catalyzes the conversion of unsaturated fatty acids to acetyl-CoA?
Which enzyme catalyzes the conversion of unsaturated fatty acids to acetyl-CoA?
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Which component plays a role in transporting Acyl-CoA into the mitochondria?
Which component plays a role in transporting Acyl-CoA into the mitochondria?
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What is the estimated energy release in kJ for 120 moles of ATP?
What is the estimated energy release in kJ for 120 moles of ATP?
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What is the role of propionyl-CoA in cellular metabolism?
What is the role of propionyl-CoA in cellular metabolism?
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What is the initial product released during the oxidation of fatty acids?
What is the initial product released during the oxidation of fatty acids?
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Which term is used to describe the oxidation that begins with the carbon adjacent to the carboxyl group?
Which term is used to describe the oxidation that begins with the carbon adjacent to the carboxyl group?
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What energetically drives the activation of fatty acids during their metabolism?
What energetically drives the activation of fatty acids during their metabolism?
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What is the role of carnitine in fatty acid oxidation?
What is the role of carnitine in fatty acid oxidation?
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What is the first reaction in the beta-oxidation cycle?
What is the first reaction in the beta-oxidation cycle?
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Which enzyme is responsible for the oxidation reaction in the acyl-CoA dehydrogenase step?
Which enzyme is responsible for the oxidation reaction in the acyl-CoA dehydrogenase step?
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What happens to acyl-carnitine in the mitochondrial matrix?
What happens to acyl-carnitine in the mitochondrial matrix?
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What is required for the complete cycle of one beta-oxidation?
What is required for the complete cycle of one beta-oxidation?
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How many cycles of beta-oxidation are needed to fully oxidize a fatty acid with 18 carbon atoms?
How many cycles of beta-oxidation are needed to fully oxidize a fatty acid with 18 carbon atoms?
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What is produced as a result of the enoyl-CoA hydratase reaction?
What is produced as a result of the enoyl-CoA hydratase reaction?
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During the β-oxidation of fatty acids, what directly results from the attack by the enzyme's Cys thiolate group?
During the β-oxidation of fatty acids, what directly results from the attack by the enzyme's Cys thiolate group?
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Which conditions are known to promote the formation of ketone bodies?
Which conditions are known to promote the formation of ketone bodies?
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What is the total ATP yield from one molecule of stearic acid (18 C) after complete oxidation?
What is the total ATP yield from one molecule of stearic acid (18 C) after complete oxidation?
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How many cycles of β-oxidation are required to break down an 18-carbon fatty acid like stearic acid?
How many cycles of β-oxidation are required to break down an 18-carbon fatty acid like stearic acid?
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What by-product is formed when acetyl-CoA is produced from β-oxidation and interacts poorly with the citric acid cycle?
What by-product is formed when acetyl-CoA is produced from β-oxidation and interacts poorly with the citric acid cycle?
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In fatty acid oxidation, how many NADH and FADH2 molecules are generated from one cycle of β-oxidation?
In fatty acid oxidation, how many NADH and FADH2 molecules are generated from one cycle of β-oxidation?
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Which of the following components is involved in the energy yield during the TCA cycle following β-oxidation?
Which of the following components is involved in the energy yield during the TCA cycle following β-oxidation?
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What is the primary reason fatty acids require activation before oxidation?
What is the primary reason fatty acids require activation before oxidation?
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Which molecule primarily serves as the starting point for calculating total ATP yield from fatty acid oxidation?
Which molecule primarily serves as the starting point for calculating total ATP yield from fatty acid oxidation?
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Study Notes
Beta Oxidation and Fatty Acid Synthesis
- Fatty acids are obtained from dietary intake and adipose tissue.
- Most dietary and adipose tissue fats are triglycerides.
- Hormones (glucagon, epinephrine, ACTH) trigger the release of fatty acids from adipose tissue.
- Lipases catalyze the hydrolysis of triacylglycerols
- Phospholipases catalyze the hydrolysis of phosphoacylglycerols
Fatty Acid Sources
- Fatty acids are obtained from food and adipose tissue.
Beta Oxidation
- Beta oxidation is a series of reactions that cleave carbon atoms two at a time from the carboxyl end of a fatty acid.
- The complete cycle of one beta-oxidation requires four enzymes:
- Reaction 1: Oxidation of the a,β carbon-carbon single bond to a carbon-carbon double bond.
- Reaction 2: Hydration of the carbon-carbon double bond.
- Reaction 3: Oxidation of the β-hydroxyl group to a carbonyl group.
- Reaction 4: Cleavage of the carbon chain by a reverse Claisen reaction.
Fatty Acid Activation
- Fatty acid oxidation begins with activation.
- A thioester bond is formed between the acyl group of the fatty acid and the thiol of CoA-SH.
- This process requires ATP hydrolysis.
Role of Carnitine
- Acyl-CoAs cross the outer mitochondrial membrane but not the inner membrane.
- Carnitine accepts the acyl group and carries it across the inner mitochondrial membrane.
- Carnitine palmitoyltransferase (CPT-1) has specificity for acyl groups between 14 and 18 carbons in length.
- In the matrix, acyl-carnitine exchanges with mitochondrial CoA-SH to reform acyl-CoA
Oxidation of Odd-Numbered Fatty Acids
- The last β-oxidation cycle of a fatty acid with an odd number of carbons gives propionyl-CoA.
Oxidation of Unsaturated Fatty Acids
- A cis-trans isomerization is needed to convert unsaturated fatty acids to acetyl-CoA, via an enzyme known as an isomerase.
Fatty Acid Degradation (Summary)
- Fatty acids are activated and transported into the mitochondrial matrix for further breakdown.
- Breakdown of fatty acids takes place in the mitochondrial matrix and proceeds by successive removal of two-carbon units as acetyl-CoA.
- Each cleavage of a two-carbon moiety requires a four-step reaction sequence called beta-oxidation
Ketone Bodies
- Formed when acetyl-CoA exceeds the amount of oxaloacetate available to react in the citric acid cycle (high fat/low carbohydrate intake).
- Ketone bodies include acetone, β-hydroxybutyrate, and acetoacetate.
- These are formed mainly in the liver mitochondria and can be used as fuel in most tissues and organs.
Fatty Acid Synthesis
- Occurs in the cytosol.
- Acetyl-CoA is transported into the cytosol.
- Acetyl-CoA is transformed to malonyl-CoA.
- Malonyl-CoA is the precursor for the biosynthesis.
- β-oxidation and fatty acid synthesis are regulated to prevent futile cycles.
Steps of Fatty Acid Synthesis
- Stage 1: Acetyl-CoA carboxylation to form malonyl-CoA.
- Step 2: Condensation.
- Step 3: Reduction.
- Step 4: Dehydration.
- Step 5: Reduction.
- Step 6 to n: Repeat steps 3-5 to add more carbons until the desired fatty acid is produced
Fatty Acid Synthase (FAS)
- The fatty acid synthase enzyme complex has several catalytic activities within the complex.
Regulation
- The synthesis and degradation of fatty acids are regulated to prevent futile cycles.
- Malonyl-CoA is a key regulator; it inhibits fatty acid degradation.
- AMP-activated protein kinase (AMPK) regulates fatty acid synthesis and degradation by regulating acetyl-CoA carboxylase (ACC).
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Description
This quiz covers the biochemical processes of beta oxidation and fatty acid synthesis. It discusses the sources of fatty acids, the role of hormones, and the specific reactions involved in beta oxidation. Test your understanding of these essential metabolic pathways.
