MBS Fatty Acid Nomenclature, Oxidation, and Ketone Bodies

What does "C18:2" represent in fatty acid nomenclature?

C18:2 refers to a fatty acid with 18 carbon atoms and 2 double bonds.

What is the significance of the symbol Δ9 in fatty acid nomenclature?

Δ9 indicates a double bond at the 9th carbon from the carboxyl end of the fatty acid chain.

What does ω-3 represent in fatty acid nomenclature?

ω-3 indicates that the first double bond in the fatty acid chain is located at the 3rd carbon from the methyl (ω) end.

Compare saturated and unsaturated fatty acids.

Saturated fatty acids have no double bonds and are solid at room temperature. Unsaturated fatty acids have one or more double bonds and are typically liquid at room temperature.

What are cis- and trans-unsaturated fatty acids?

Cis-unsaturated fatty acids have hydrogen atoms on the same side of the double bond, while trans-unsaturated fatty acids have hydrogen atoms on opposite sides of the double bond.

What is lipolysis?

Lipolysis is the breakdown of triglycerides into fatty acids and glycerol, providing energy during fasting and exercise.

What are the three main types of lipases involved in lipolysis?

The three main types are Adipose Triglyceride Lipase (ATGL), Hormone-sensitive Lipase (HSL), and Monoacylglycerol Lipase (MGL).

How does insulin regulate lipolysis?

Insulin inhibits both ATGL and HSL, thus preventing lipolysis in the fed state.

How do fatty acids move between tissues in the body?

In the fed state, fatty acids move from food to adipose tissue. In the fasting state, fatty acids are released from adipose tissue to organs like the liver and muscle.

What is the role of CoA, carnitine, and malonyl-CoA in fatty acid uptake into mitochondria?

CoA is needed to form fatty acyl-CoA for oxidation; carnitine helps transport fatty acyl-CoA into mitochondria; malonyl-CoA inhibits fatty acid uptake into mitochondria.

What is the overall purpose of fatty acid β-oxidation?

break down fatty acids into Acetyl-CoA, NADH, and FADH2 for ATP production.

Where does fatty acid β-oxidation occur?

mitochondria.

How is ATP produced from palmitate versus glucose?

Palmitate yields more ATP than glucose due to its higher carbon content and the energy produced in β-oxidation and the citric acid cycle.

What are the main sources of Acetyl-CoA in a cell?

Acetyl-CoA can come from fatty acid β-oxidation, glucose metabolism (via pyruvate), and ketogenic amino acids.

What is the purpose of ketone body synthesis?

Ketone bodies are synthesized during fasting to provide an alternative energy source, especially for the brain

Where does ketone body synthesis occur?

liver mitochondria.

What is the purpose of ketone body oxidation?

Ketone body oxidation converts ketone bodies into Acetyl-CoA, which enters the citric acid cycle for energy production.

What tissues use ketone bodies?

brain, heart, skeletal muscle, and kidneys, but not by the liver.

What is the difference between ketosis and ketoacidosis?

Ketosis is a normal state of increased ketone production during fasting, while ketoacidosis is a pathological condition where ketone production exceeds their use, leading to harmful high levels of ketones in the blood.

What is ketotic hypoglycemia?

characterized by low blood glucose and high ketone levels in the blood or urine, typically occurring during prolonged fasting or in metabolic disorders.

What is non-ketotic hypoglycemia?

characterized by low blood glucose and low ketone levels, often due to excessive insulin secretion or insulinoma.

What are the two main types of fat in the body?

The two types are dietary fat (from food, contributing to ~20-35% of daily calories) and fat in adipose tissue (making up about 25-30% of body weight).

What is the function of lipolysis?

provides energy by breaking down triglycerides into fatty acids and glycerol, which are released into the bloodstream and used for energy, or converted into glucose and ketone bodies.

What is the role of fatty acid binding proteins (FABPs)?

FABPs bind to fatty acids inside cells, helping to transport and regulate the movement of fatty acids to prevent toxicity.

How are free fatty acids toxic?

act as noxious detergents, interacting with hydrophobic substances. In the blood, they are bound to albumin to prevent toxicity, while inside cells, they are bound to FABPs.

What is the effect of malonyl-CoA on fatty acid oxidation?

Malonyl-CoA inhibits fatty acid uptake into mitochondria, thus inhibiting β-oxidation.

How does insulin influence fatty acid metabolism?

Insulin inhibits lipolysis, β-oxidation, and fatty acid uptake into mitochondria, promoting fat storage and reducing the breakdown of fatty acids.

What is the energetic yield from the β-oxidation of palmitate (C16)?

From palmitate, β-oxidation yields 8 acetyl-CoA molecules, 7 NADH, and 7 FADH2 after 7 cycles of oxidation.

What is the overflow pathway in ketone body synthesis?

occurs when excess Acetyl-CoA, generated from fatty acid β-oxidation, is used to synthesize ketone bodies in the liver during periods of high lipolysis and fasting.

What are the primary ketone bodies produced in the liver?

Acetoacetate, β-hydroxybutyrate, and acetone (the latter being formed through spontaneous conversion of acetoacetate).

How does glucose sparing work in the body during fasting?

the inhibition of glucose oxidation by fatty acid oxidation and ketolysis, ensuring that glucose is reserved primarily for tissues that require it, such as the brain.

What does ketosis indicate about a person's metabolic state?

indicates a state of increased ketone body production, typically occurring after 2-3 days of fasting or on a low-carbohydrate diet, where the body uses ketone bodies for energy instead of glucose.

What causes ketoacidosis and why is it dangerous?

occurs when ketone production exceeds ketone usage, leading to an accumulation of ketones in the blood.

It is dangerous because it causes a severe drop in blood pH and can lead to life-threatening complications, especially in uncontrolled diabetes.

What is the role of glucagon in fatty acid metabolism?

Glucagon stimulates lipolysis and fatty acid release from adipose tissue during fasting, providing fuel for energy production.

Why can't the liver use ketone bodies for energy?

The liver lacks the enzyme thiophorase, which is required for ketone body oxidation, so it cannot utilize ketone bodies for energy, but can synthesize them.

What happens to the blood levels of ketone bodies during prolonged fasting?

the blood levels of ketone bodies increase, reaching concentrations of around 5 mM as the body shifts to using fat for energy.

How do insulin and ketone bodies interact in a healthy individual?

In a healthy individual, ketone bodies stimulate insulin secretion after a few days of fasting, which then inhibits lipolysis, thus limiting ketone body production and preventing excess ketone accumulation.

What are the symptoms of ketotic hypoglycemia?

shakiness, confusion, lethargy, nausea, vomiting, abdominal pain, and fruity-smelling breath. It is usually caused by prolonged fasting, metabolic disorders, or a ketogenic diet.

What are the common causes of non-ketotic hypoglycemia?

caused by excess insulin secretion, insulinoma (pancreatic tumors), or fatty acid oxidation disorders, and is characterized by low blood glucose and low ketone levels.

What is the function of fatty acids in the body?

serve as an energy source (through β-oxidation), are components of triglycerides and phospholipids, and act as precursors for post-translational modifications.

What is the difference between lipolysis and fat absorption?

Lipolysis is the breakdown of triglycerides into fatty acids and glycerol, occurring mainly during fasting or exercise.

Fat absorption refers to the process of taking dietary fat from the digestive tract into the body.

What is the role of lipoprotein lipase in fatty acid metabolism?

helps release fatty acids from triglycerides in lipoproteins, allowing them to be taken up by tissues for energy or storage.

What happens during β-oxidation of fatty acids?

involves the breakdown of fatty acids into Acetyl-CoA, NADH, and FADH2, which are used to produce ATP through the citric acid cycle and oxidative phosphorylation.

Why does acetyl-CoA accumulate during high rates of lipolysis?

High lipolysis generates large amounts of Acetyl-CoA from fatty acid β-oxidation. When the citric acid cycle is saturated, Acetyl-CoA is diverted to ketone body synthesis.

How does the liver contribute to ketone body production?

The liver synthesizes ketone bodies (Acetoacetate, β-hydroxybutyrate, and acetone) from Acetyl-CoA during periods of fasting or carbohydrate deprivation when glucose availability is low.

What role does AMP play in fatty acid uptake into mitochondria?

High levels of AMP stimulate the uptake of fatty acids into mitochondria, promoting β-oxidation and energy production during exercise or fasting.

What is the difference between acetone and other ketone bodies like Acetoacetate and β-hydroxybutyrate?

Acetone is produced spontaneously from Acetoacetate and is exhaled,

while Acetoacetate and β-hydroxybutyrate are enzymatically synthesized and used as energy sources.

How does insulin influence ketogenesis?

inhibits lipolysis and ketogenesis in the fed state by reducing fatty acid release from adipocytes, limiting the substrate needed for ketone body synthesis.

What are the two types of hypoglycemia, and how are they distinguished?

Ketotic hypoglycemia is characterized by low glucose and high ketones,

while non-ketotic hypoglycemia is characterized by low glucose and low ketones, often due to excessive insulin secretion.

What is the role of NADH and FADH2 in energy production from fatty acids?

NADH and FADH2 are produced during β-oxidation and enter the electron transport chain, where they generate ATP through oxidative phosphorylation.