Chapter 22- Biochemistry Ketogenesis

What is the main purpose of fatty acid oxidation in mitochondria?

To generate large amounts of energy by breaking down fatty acids to acetyl-CoA.

What are ketone bodies and what are the three main types?

Ketone bodies are acetoacetate, D-3-hydroxybutyrate, and acetone, produced during fatty acid breakdown.

What condition is characterized by the overproduction of ketone bodies?

Ketosis, which can lead to ketoacidosis if prolonged.

What is the role of carnitine in fatty acid metabolism?

Carnitine allows long-chain fatty acids to cross the inner mitochondrial membrane.

What enzyme converts free fatty acids to acyl-CoA, and what is its significance?

Acyl-CoA synthetase converts fatty acids to acyl-CoA, the active form required for fatty acid catabolism.

What happens to acetyl-CoA in the citric acid cycle?

Acetyl-CoA is oxidized to produce CO2 and ATP.

During starvation, what happens to the activity of carnitine palmitoyltransferase-I (CPT-I)?

CPT-I activity increases, promoting fatty acid oxidation.

What is the net gain of ATP from the complete oxidation of 1 mol of palmitate?

The net gain is 106 mol of ATP after accounting for the energy used in activation.

How does diabetes mellitus affect ketone body production?

Diabetes can lead to excessive production of ketone bodies, contributing to ketoacidosis.

What are the implications of carnitine deficiency?

Carnitine deficiency can lead to impaired fatty acid oxidation and hypoglycemia.

What is the consequence of excessive insulin in fatty acid metabolism?

Excess insulin can suppress fatty acid oxidation and promote esterification into fat.

What is refsum disease and its associated metabolic defect?

Refsum disease is caused by the accumulation of phytanic acid due to a defect in its metabolism.

In what conditions is ketogenesis favored?

Ketogenesis is favored during starvation and uncontrolled diabetes due to high levels of free fatty acids.

How do extrahepatic tissues utilize ketone bodies?

Extrahepatic tissues convert ketone bodies like acetoacetate back into acetyl-CoA for energy.

What role do NADH and FADH2 play in fatty acid oxidation?

Both NADH and FADH2 are generated during the β-oxidation process and are used to produce ATP via oxidative phosphorylation.

What is the primary energy source for the body during rest?

The body primarily uses fatty acids for energy during rest.

What triggers lipolysis in adipose tissue?

Lipolysis is triggered by hormones like glucagon and epinephrine.

What role do ketone bodies play during prolonged fasting?

Ketone bodies serve as an alternative energy source for the brain and other tissues during prolonged fasting.

Where does fatty acid synthesis primarily occur?

Fatty acid synthesis primarily occurs in the liver and adipose tissue.

What is the function of malonyl-CoA in fatty acid synthesis?

Malonyl-CoA acts as a substrate and also inhibits the transport of fatty acids into mitochondria.

What are the end products of complete fatty acid oxidation?

The end products are acetyl-CoA, NADH, FADH2, and CO2.

How many cycles does it take to completely oxidize a saturated fatty acid with 16 carbons?

It takes 7 cycles of β-oxidation to completely oxidize a saturated fatty acid with 16 carbons.

What is the significance of the carnitine shuttle?

The carnitine shuttle transports long-chain fatty acids into the mitochondria for oxidation.

What metabolic pathway produces d-3-hydroxybutyrate?

D-3-hydroxybutyrate is produced during ketogenesis from acetyl-CoA.

What is the primary purpose of the citric acid cycle?

The citric acid cycle generates reducing equivalents (NADH and FADH2) for ATP production.

What factors can increase the rate of β-oxidation?

Increased rates of β-oxidation can be stimulated by fasting and exercise.

What is the main ketone body produced during starvation?

Acetoacetate is the main ketone body produced during starvation.

What is the relationship between insulin and fatty acid synthesis?

Insulin promotes fatty acid synthesis by enhancing the expression of lipogenic enzymes.

How do free fatty acids enter cells for metabolism?

Free fatty acids enter cells by diffusion or through specific transport proteins.

What happens to excess carbohydrates in the liver?

Excess carbohydrates are converted to fat through a process called de novo lipogenesis.

What enzyme is responsible for ketogenesis?

The enzyme HMG-CoA synthase is primarily responsible for ketogenesis.

What is the role of acyl-CoA in fatty acid metabolism?

Acyl-CoA is the activated form of fatty acids necessary for their metabolism.

What consequence does a deficiency of acyl-CoA synthetase have?

A deficiency can result in decreased fatty acid oxidation and energy production.

How are ketone bodies utilized by the brain?

The brain converts ketone bodies back into acetyl-CoA for energy production.

What is the role of FAD in the β-oxidation of fatty acids?

FAD acts as an electron acceptor, forming FADH2 during β-oxidation.

How do high levels of sugar affect lipid metabolism?

High levels of sugar can increase lipid storage and decrease fatty acid oxidation.

What is the function of the enzyme thiolase in fatty acid metabolism?

Thiolase catalyzes the final step of β-oxidation, producing acetyl-CoA.

What is the purpose of energy investment in fatty acid synthesis?

Energy investment in fatty acid synthesis is required for the activation of acetate to form malonyl-CoA.

How does starvation affect glucose and fatty acid metabolism?

During starvation, glucose metabolism decreases, and fatty acid oxidation increases.

What is the fate of excess acetyl-CoA produced from fatty acid oxidation in the liver?

Excess acetyl-CoA is converted to ketone bodies for energy supply to other tissues.

What type of fatty acids can lead to metabolic disorders if excessively consumed?

Excess consumption of trans fats can lead to metabolic disorders and cardiovascular disease.

What health conditions can result from the overproduction of ketone bodies?

Overproduction can lead to ketoacidosis, especially in uncontrolled diabetes.

How does hypothyroidism affect fatty acid metabolism?

Hypothyroidism can lead to decreased fatty acid oxidation and increased lipid storage.

What are the consequences of an impaired carnitine shuttle?

Impaired carnitine shuttle can result in fatty acid accumulation and muscle weakness.

How do statins affect fatty acid metabolism?

Statins lower plasma cholesterol levels and can also affect fatty acid metabolism.

What enzyme converts acetoacetate to d-3-hydroxybutyrate?

The enzyme d-3-hydroxybutyrate dehydrogenase converts acetoacetate to d-3-hydroxybutyrate.

What is the effect of prolonged high insulin levels on fat metabolism?

Prolonged high insulin levels can suppress lipolysis and promote fat storage.

What is the metabolic fate of linoleic acid in the body?

Linoleic acid is converted into arachidonic acid and subsequently into signaling molecules.

What is the primary role of fatty acid oxidation in energy metabolism?

To produce ATP by converting fatty acids into acetyl-CoA.

What are the key products generated during fatty acid oxidation?

Acetyl-CoA, NADH, and FADH2.

Why is acetyl-CoA important in metabolism?

Acetyl-CoA enters the citric acid cycle for energy production.

How does the citric acid cycle relate to fatty acid oxidation?

It utilizes acetyl-CoA to generate NADH and FADH2 for ATP production.

What is the main function of carnitine in fatty acid metabolism?

To transport long-chain fatty acids into mitochondria.

What triggers the release of free fatty acids from adipose tissue?

Hormones like glucagon and epinephrine stimulate lipolysis.

What metabolic state increases ketone body production?

Starvation or uncontrolled diabetes.

What is the relationship between insulin and fatty acid oxidation?

Insulin inhibits fatty acid oxidation and promotes storage.

What are the consequences of high levels of insulin?

Suppressed lipolysis and increased fat storage.

What health issue results from inadequate carnitine levels?

Carnitine deficiency can lead to impaired fatty acid oxidation.

What happens to free fatty acids before they are oxidized?

They are activated to acyl-CoA by acyl-CoA synthetase.

What body tissues use ketone bodies for energy?

Brain, muscles, and other tissues during prolonged fasting.

How is energy produced from NADH and FADH2?

They are used in oxidative phosphorylation to generate ATP.

What is the main type of fatty acid carbon structure?

Saturated and unsaturated fatty acids.

How does prolonged fasting affect fatty acid metabolism?

Fatty acid oxidation increases while glucose metabolism decreases.

What is the impact of hypothyroidism on lipid metabolism?

It leads to decreased fatty acid oxidation and increased lipid storage.

What metabolic disorders are associated with trans fat intake?

Increased risk of cardiovascular disease and metabolic syndrome.

What is the significance of the enzyme HMG-CoA synthase?

It catalyzes the first step in ketogenesis.

What does excessive production of ketone bodies lead to?

Ketoacidosis, particularly in uncontrolled diabetes.

How do extrahepatic tissues process ketone bodies?

They convert ketone bodies back into acetyl-CoA for energy.

What enzyme catalyzes the conversion of acetoacetate to d-3-hydroxybutyrate?

D-3-hydroxybutyrate dehydrogenase.

What is de novo lipogenesis?

The conversion of excess carbohydrates into fatty acids.

When does ketogenesis primarily occur?

During periods of low carbohydrate intake and high fatty acid availability.

What are the symptoms of ketosis?

Fatigue, weakness, dehydration, and fruity breath odor.

What types of fatty acids primarily come from dietary sources?

Essential fatty acids like omega-3 and omega-6.

How does exercise influence fatty acid metabolism?

It increases the rate of fatty acid oxidation.

What is the fate of excess fatty acids in the liver?

They can be converted to ketone bodies or stored as triglycerides.

What role does malonyl-CoA play in fatty acid metabolism?

It inhibits fatty acid transport into mitochondria for oxidation.

What is the importance of maintaining balanced fatty acid levels?

To prevent metabolic disorders and ensure proper energy metabolism.

How does the body respond to high sugar intake in terms of fat storage?

Increased sugar can lead to enhanced lipogenesis and fat storage.

What is the effect of fasting on carnitine levels?

Fasting may increase peripheral carnitine availability for fatty acid oxidation.

What happens during the β-oxidation of fatty acids?

Fatty acids are progressively broken down to acetyl-CoA units.