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Questions and Answers
A deficiency in the enzyme ETF:QO would most significantly impair the metabolic process associated with which of the following?
A deficiency in the enzyme ETF:QO would most significantly impair the metabolic process associated with which of the following?
Approximately how many ATP molecules can be generated through the complete oxidation of one mole of C18:0 fatty acid?
Approximately how many ATP molecules can be generated through the complete oxidation of one mole of C18:0 fatty acid?
Which series of reactions accurately describes the beta-oxidation of fatty acids?
Which series of reactions accurately describes the beta-oxidation of fatty acids?
In the context of elevated ketone bodies, how would a person with untreated type 1 diabetes differ from an individual on a severe diet when comparing their blood laboratory results?
In the context of elevated ketone bodies, how would a person with untreated type 1 diabetes differ from an individual on a severe diet when comparing their blood laboratory results?
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During which of the following scenarios would fatty acids primarily serve as the body's energy source?
During which of the following scenarios would fatty acids primarily serve as the body's energy source?
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What laboratory finding is most likely in a patient with classic carnitine palmitoyltransferase II deficiency?
What laboratory finding is most likely in a patient with classic carnitine palmitoyltransferase II deficiency?
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A 6-month-old infant experiencing frequent crying, lethargy, and poor eating, particularly after infections, where symptoms are reduced with frequent feeding, might be showing signs of which metabolic condition?
A 6-month-old infant experiencing frequent crying, lethargy, and poor eating, particularly after infections, where symptoms are reduced with frequent feeding, might be showing signs of which metabolic condition?
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Which of the following is a function of glutamate in the kidney?
Which of the following is a function of glutamate in the kidney?
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During the urea cycle, how many high-energy phosphate bonds are utilized for a single complete cycle?
During the urea cycle, how many high-energy phosphate bonds are utilized for a single complete cycle?
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Which of the following accurately describes the role of glutamine in the intestine?
Which of the following accurately describes the role of glutamine in the intestine?
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What is the fate of one molecule of alanine during gluconeogenesis?
What is the fate of one molecule of alanine during gluconeogenesis?
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Which statement correctly describes the transfer of citrulline and ornithine across the mitochondrial membrane during the urea cycle?
Which statement correctly describes the transfer of citrulline and ornithine across the mitochondrial membrane during the urea cycle?
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A child's blood work indicates hypoglycemia and hypoketosis, with elevated levels of six to eight carbon-chain dicarboxylic acids and acylcarnitines in the urine. Which enzyme is most likely defective?
A child's blood work indicates hypoglycemia and hypoketosis, with elevated levels of six to eight carbon-chain dicarboxylic acids and acylcarnitines in the urine. Which enzyme is most likely defective?
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Vitamin B12 is essential for the complete oxidation of which type of fatty acids?
Vitamin B12 is essential for the complete oxidation of which type of fatty acids?
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A patient in diabetic ketoacidosis has a distinct odor on their breath. Which compound is responsible for this?
A patient in diabetic ketoacidosis has a distinct odor on their breath. Which compound is responsible for this?
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Which of the following is directly involved in triacylglycerol synthesis in adipose tissue?
Which of the following is directly involved in triacylglycerol synthesis in adipose tissue?
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A palmitic acid molecule is ingested, digested, stored, and ultimately oxidized to $CO_2$ and $H_2O$. In which molecular complex is the palmitate transported from the gut lumen to the gut epithelial cell?
A palmitic acid molecule is ingested, digested, stored, and ultimately oxidized to $CO_2$ and $H_2O$. In which molecular complex is the palmitate transported from the gut lumen to the gut epithelial cell?
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A patient with hyperlipoproteinemia would likely benefit from a low-carbohydrate diet if which lipoproteins are elevated in their blood?
A patient with hyperlipoproteinemia would likely benefit from a low-carbohydrate diet if which lipoproteins are elevated in their blood?
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In patients with MCAD deficiency, fasting hypoglycemia occurs because, under fasting conditions, which gluconeogenic enzyme may not be fully activated?
In patients with MCAD deficiency, fasting hypoglycemia occurs because, under fasting conditions, which gluconeogenic enzyme may not be fully activated?
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Why are newly synthesized fatty acids not immediately degraded in cells?
Why are newly synthesized fatty acids not immediately degraded in cells?
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In humans, prostaglandins are primarily derived from which precursor?
In humans, prostaglandins are primarily derived from which precursor?
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Individuals with glucose 6-phosphate dehydrogenase deficiency still produce NADPH for fatty acid synthesis. Which enzyme enables this process?
Individuals with glucose 6-phosphate dehydrogenase deficiency still produce NADPH for fatty acid synthesis. Which enzyme enables this process?
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Which drug covalently modifies and inactivates both COX-1 and COX-2 enzymes?
Which drug covalently modifies and inactivates both COX-1 and COX-2 enzymes?
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Which of the following is formed from sphingolipids?
Which of the following is formed from sphingolipids?
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Low-dose aspirin is used to prevent platelet aggregation by blocking the formation of which eicosanoid?
Low-dose aspirin is used to prevent platelet aggregation by blocking the formation of which eicosanoid?
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The statin class of drugs inhibits cholesterol synthesis. Which metabolite would accumulate in the pathway when taking a statin?
The statin class of drugs inhibits cholesterol synthesis. Which metabolite would accumulate in the pathway when taking a statin?
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Which statement correctly describes a function of a cholesterol precursor, cholesterol itself, or a product derived from cholesterol?
Which statement correctly describes a function of a cholesterol precursor, cholesterol itself, or a product derived from cholesterol?
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A person decreases fat intake and increases carbohydrate intake while maintaining the same total caloric intake. Which blood lipoprotein level would MOST likely decrease?
A person decreases fat intake and increases carbohydrate intake while maintaining the same total caloric intake. Which blood lipoprotein level would MOST likely decrease?
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Under which of the following circumstances will an individual gain weight MOST rapidly, assuming they are consuming excess calories?
Under which of the following circumstances will an individual gain weight MOST rapidly, assuming they are consuming excess calories?
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A chronic alcoholic with a severe hypoglycemic episode is found to have elevated VLDL levels. Which underlying cause best explains this?
A chronic alcoholic with a severe hypoglycemic episode is found to have elevated VLDL levels. Which underlying cause best explains this?
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A patient with abetalipoproteinemia experiences difficulty maintaining blood volume and blood clotting. This is MOST likely due to an inability to produce which lipoprotein?
A patient with abetalipoproteinemia experiences difficulty maintaining blood volume and blood clotting. This is MOST likely due to an inability to produce which lipoprotein?
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A person with type 1 diabetes, neglecting insulin for 2 days while eating normally, would have elevated circulating triglycerides due to which of the following?
A person with type 1 diabetes, neglecting insulin for 2 days while eating normally, would have elevated circulating triglycerides due to which of the following?
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Under conditions of a low insulin/glucagon ratio, which allosteric modifier in muscle will result in stimulation of both glycolysis and fatty acid oxidation?
Under conditions of a low insulin/glucagon ratio, which allosteric modifier in muscle will result in stimulation of both glycolysis and fatty acid oxidation?
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Which is a major difference between patients with type 1 and type 2 diabetes?
Which is a major difference between patients with type 1 and type 2 diabetes?
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After running 5 miles, a marathon trainee is MOST likely using which energy source for ATP generation in the muscles?
After running 5 miles, a marathon trainee is MOST likely using which energy source for ATP generation in the muscles?
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The nitrogens in urea are directly derived from which of the following pairs of compounds?
The nitrogens in urea are directly derived from which of the following pairs of compounds?
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Which of the following enzymes is capable of fixing ammonia into an organic molecule?
Which of the following enzymes is capable of fixing ammonia into an organic molecule?
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During high rates of protein turnover, the carbons of glutamine, used as a nitrogen carrier, can be used for gluconeogenesis. Which enzyme would be required?
During high rates of protein turnover, the carbons of glutamine, used as a nitrogen carrier, can be used for gluconeogenesis. Which enzyme would be required?
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The activation of drugs like sodium benzoate and phenylbutyrate used to treat urea-cycle defects are most similar to which metabolic process?
The activation of drugs like sodium benzoate and phenylbutyrate used to treat urea-cycle defects are most similar to which metabolic process?
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Which of the following foods is highest in the vitamin that acts as the required cofactor for transamination reactions?
Which of the following foods is highest in the vitamin that acts as the required cofactor for transamination reactions?
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How would you describe the release of amino acid nitrogen as NH4+?
How would you describe the release of amino acid nitrogen as NH4+?
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The primary mechanism by which statin medications reduce circulating cholesterol levels involves which of the following?
The primary mechanism by which statin medications reduce circulating cholesterol levels involves which of the following?
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A patient with abetalipoproteinemia develops hepatic steatosis (fatty liver) due to which of the following?
A patient with abetalipoproteinemia develops hepatic steatosis (fatty liver) due to which of the following?
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Which of the following correctly pairs a hormone with its stimulatory hormone and its site of synthesis?
Which of the following correctly pairs a hormone with its stimulatory hormone and its site of synthesis?
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For bile salts to be excreted in the stool, which of the following processes must occur?
For bile salts to be excreted in the stool, which of the following processes must occur?
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What is the primary metabolic fate of acetate, which is a product of ethanol metabolism?
What is the primary metabolic fate of acetate, which is a product of ethanol metabolism?
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Which of the following metabolic changes is most likely to occur after acute alcohol ingestion?
Which of the following metabolic changes is most likely to occur after acute alcohol ingestion?
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The drug disulfiram deters alcohol consumption by which of the following mechanisms?
The drug disulfiram deters alcohol consumption by which of the following mechanisms?
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Induction of the CYP2E1 enzyme results in which of the following?
Induction of the CYP2E1 enzyme results in which of the following?
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Which of the following consequences of chronic alcohol consumption is considered irreversible?
Which of the following consequences of chronic alcohol consumption is considered irreversible?
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In a chronic alcoholic experiencing severe hypoglycemia, gluconeogenic precursors are trapped. Which of the following is a trapped intermediate?
In a chronic alcoholic experiencing severe hypoglycemia, gluconeogenic precursors are trapped. Which of the following is a trapped intermediate?
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A patient with a vitamin deficiency secondary to chronic alcoholism is most likely to exhibit trouble with which of the following reactions due to this deficiency?
A patient with a vitamin deficiency secondary to chronic alcoholism is most likely to exhibit trouble with which of the following reactions due to this deficiency?
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An individual with a slow-activity isozyme of which enzyme would most likely exhibit low alcohol tolerance and thus rarely drink?
An individual with a slow-activity isozyme of which enzyme would most likely exhibit low alcohol tolerance and thus rarely drink?
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In a person with a defect preventing the entry of ethanol metabolites into the mitochondria, what is the expected outcome?
In a person with a defect preventing the entry of ethanol metabolites into the mitochondria, what is the expected outcome?
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The production of reactive oxygen species (ROS) during ethanol metabolism is most directly linked to which of the following enzyme systems?
The production of reactive oxygen species (ROS) during ethanol metabolism is most directly linked to which of the following enzyme systems?
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A diabetic patient presents with hyperglycemia, ketonemia, and acetone breath. Which of the following statements about this patient is correct?
A diabetic patient presents with hyperglycemia, ketonemia, and acetone breath. Which of the following statements about this patient is correct?
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Study Notes
Fatty Acid Metabolism
- ETF:QO deficiency: Leads to reduced energy yield from fatty acid use, potentially causing death.
- C18:0 fatty acid oxidation: Yields approximately 125 ATP.
- Fatty acid oxidation reactions: Oxidation, hydration, oxidation, then carbon-carbon bond breaking.
- Ketone bodies in diabetes vs. diet: Elevated in both, but distinguishing factor is glucose levels being very high in diabetes, and low in diet. Also, six- and eight-carbon dicarboxylate levels are elevated in individuals on severe diets.
- Fatty acids as fuel source: Major source during prolonged exercise (e.g., last mile of a marathon).
- Carnitine palmitoyltransferase II deficiency: Results in elevated blood acylcarnitine levels.
- Infant symptoms and enzyme deficiency: Symptoms of hypoglycemia, hypoketosis, and presence of six to eight carbon-chain dicarboxylic acids and acylcarnitine in urine suggest MCAD or CPTII deficiency.
- Vitamin B12 requirement in fatty acid oxidation: Essential for the complete oxidation of very-long-chain fatty acids .
- Breath odor in ketoacidosis: Acetone.
Lipid Metabolism
- Triacylglycerol synthesis: Involves fatty acids from chylomicrons and VLDL, glycerol-3-P, and the formation of ester bonds. Not 2-monoacylglycerol or acetoacyl-CoA as obligatory intermediate.
- Palmitate transport: Carried as a fatty acid–albumin complex in the blood stream.
- Hyperlipoproteinemia and low-carbohydrate diet: Most beneficial in conditions with elevated VLDL and/or LDL.
- MCAD deficiency and fasting hypoglycemia: Impaired gluconeogenesis due to lack of fully activated pyruvate carboxylase.
- Fatty acid synthesis and degradation: Fatty acid synthesis and degradation are regulated differently so newly synthesized fatty acids are not immediately broken down. This is due to insulin's inhibition of fatty acid degradation and enzyme induction/transport regulation during synthesis.
- Prostaglandin source: Arachidonic acid.
- NADPH synthesis and fatty acid synthesis: Glucose-6-Phosphate dehydrogenase is a part of NADPH synthesis, but other enzymes are involved in the synthesis of fatty acids.
- COX enzyme inhibitors: Aspirin acts as both a cyclooxygenase (COX) inhibitor (the mechanism of action is a covalent modification).
- Sphingolipid derivative: Myelin sheath.
- Low-dose aspirin: Prevents platelet aggregation by inhibiting thromboxane formation.
Cholesterol Metabolism
- Statin mechanism: Block HMG-CoA reductase, leading to accumulation of HMG-CoA, which is a precursor needed to form mevalonate.
- Cholesterol function: Precursors are converted to vitamin D and cholesterol is a precursor for steroid hormones.
- LDL Cholesterol calculation: Calculated from total cholesterol, HDL, and triglycerides: Total cholesterol − HDL − (triglycerides/5).
- LPL cofactor: ApoCII.
- Lipoprotein density order: HDL (most dense) < LDL < VLDL < chylomicrons (least dense).
- Microsomal triglyceride transfer protein (MTP) deficiency: Results in elevated chylomicrons, causing steatorrhea.
- LDL reduction treatment: Upregulation of LDL receptors by statins leads to reduced circulating cholesterol levels.
- Abetalipoproteinemia and fatty liver: Inability to produce chylomicrons and VLDL leads to hepatic steatosis.
- Steroid excretion: Bile salts are excreted in stool, through the deconjugation by intestinal bacteria.
Alcohol Metabolism
- Ethanol metabolism product fate: Acetate is taken up by cells and converted to acetyl-CoA.
- Acute alcohol ingestion outcome: Leads to lactic acidosis and decreased NAD+ levels; there is inhibition of ketogenesis
- Disulfiram mechanism: Inhibits the conversion of acetaldehyde to acetate, causing acetaldehyde to accumulate.
- CYP2E1 induction: Increases ethanol clearance and leads to an increased risk of liver damage and free radical production.
- Irreversible consequence of chronic alcohol consumption: Liver cirrhosis.
- Hypoglycemia in chronic alcoholics: Gluconeogenic precursors are trapped, preventing glucose from being formed.
- Vitamin deficiency in alcoholics: Often affects reactions requiring thiamine (B1), leading to issues with carbohydrate metabolism.
- Slow alcohol metabolism isozyme: Acetaldehyde dehydrogenase.
- Mitochondrial entry defect in ethanol metabolism: Acetaldehyde would accumulate.
- ROS generation in ethanol metabolism: via MEOS.
Diabetes and Fuel Metabolism
- Diabetic ketoacidosis symptoms: Features high blood glucose, strongly positive ketone bodies in urine, acetone breath odor.
- Low-fat diet effect on blood lipoproteins: Decreases VLDL.
- Rapid weight gain and calorie source: Weight gain occurs most rapidly with excess carbohydrate intake.
- Chronic alcohol consumption and hypoglycemia: Elevated VLDL blood levels due to elevated NADH and increased apoB-100 gene transcription.
- Abetalipoproteinemia and blood volume: Associated with clotting issues due to the inability to synthesize necessary proteins for adequate blood clotting.
- Liver metabolism after carbohydrate meal then fasting: Glycolysis, glycogen synthesis, lipolysis, glycogenolysis, gluconeogenesis occurs after a meal, followed by fasting.
- Type 1 diabetes and neglected insulin: Elevated triglycerides because of reduced LPL release from muscle and fat.
- Low insulin/glucagon and metabolic outcome in muscle: Activation of both glycolysis and fatty acid oxidation because of the AMP level activation.
- Type 1 vs. type 2 diabetes: Type 1 has low insulin levels, type 2 is characterized by insulin resistance.
- Marathon training and ATP generation: Muscle glycogen is the primary source of ATP after running 5 miles.
Nitrogen Metabolism
- Urea nitrogen source: Ornithine and aspartate.
- Enzyme fixing ammonia into organic molecule Glutamate dehydrogenase.
- Glutamine as nitrogen carrier: Glutamine is used to transfer nitrogen, and the remaining carbons are used in gluconeogenesis, requiring pyruvate carboxylase.
- Urea cycle defect drug activation: Similar to fatty acid activation.
- Vitamin needed for transamination: Vitamin B6 (pyridoxine).
- Amino acid nitrogen release: Glutaminase converts glutamine to glutamate and ammonia. Ammonia does NOT freely diffuse across membranes.
- Rapid amino acid degradation and ammonia removal: Glutamine is produced by glutamate and ammonia; then it is further broken down into ammonia and glutamate via glutaminase.
- Urea cycle steps: Citrulline is synthesized in the cytosol and generated from ornithine and initiates/regenerated by the cycle.
- Alanine and gluconeogenesis: One alanine creates one molecule of glucose and one molecule of urea.
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Description
Test your knowledge on metabolic processes, specifically focusing on fatty acid oxidation and related conditions. This quiz covers key topics such as enzyme deficiencies, ATP generation, and the functions of metabolites. Perfect for students studying biochemistry or medical students preparing for exams.
