Fatty Acid Catabolism Overview
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Questions and Answers

What is the net utilization of high-energy bonds when a fatty acid molecule is activated?

  • One ATP molecule is converted to ADP.
  • Two ATP molecules are converted to AMP.
  • One ATP molecule is converted to AMP. (correct)
  • Two ATP molecules are converted to ADP.

In the context of fatty acid oxidation, where does the conversion of fatty acyl-CoA to acyl-carnitine occur?

  • Cytoplasm
  • Inner mitochondrial membrane (correct)
  • Mitochondrial matrix
  • Outer mitochondrial membrane

What is the significance of the β-carbon in β-oxidation of fatty acids?

  • It undergoes successive oxidations in the removal of two carbon atoms. (correct)
  • It is the point of attachment of coenzyme A.
  • It is the carbon atom at the carboxyl end of the fatty acyl-CoA.
  • It is the carbon atom where the double bond is formed during desaturation.

What is the primary energy source for the brain when the body is in a state of starvation for more than 4 days?

<p>Ketone bodies (C)</p> Signup and view all the answers

Carnitine, essential for fatty acid transport into mitochondria, is derived from which amino acids?

<p>Methionine and lysine (A)</p> Signup and view all the answers

What condition arises when ketone bodies accumulate in the body at a high rate, overwhelming the kidney's ability to remove them?

<p>Ketoacidosis (C)</p> Signup and view all the answers

Which of the following is NOT a ketone body produced by the liver?

<p>Pyruvate (B)</p> Signup and view all the answers

What is the primary effect of a low-carbohydrate, high-protein diet on the body's energy production?

<p>It forces the body to rely on fat for energy. (A)</p> Signup and view all the answers

Which of the following conditions cause the body to rely more heavily on fatty acids for energy?

<p>Low blood glucose (B)</p> Signup and view all the answers

What is the primary role of ketone bodies in the body?

<p>To provide energy to the brain when glucose levels are low. (C)</p> Signup and view all the answers

Which of the following is NOT a substrate used by the liver for gluconeogenesis?

<p>Acetyl-CoA (C)</p> Signup and view all the answers

What is the primary role of the liver in response to low blood glucose levels?

<p>Conversion of fatty acids into ketone bodies (D)</p> Signup and view all the answers

What process is triggered in the liver to supply glucose to the brain during starvation or a low-carbohydrate diet?

<p>Gluconeogenesis (B)</p> Signup and view all the answers

Besides the two primary ketone bodies (acetoacetate and beta-hydroxybutyrate), what is the third ketone body produced by the liver?

<p>Acetone (B)</p> Signup and view all the answers

What is the primary reason why ketone bodies can accumulate in the body during a ketogenic diet?

<p>Reduced glucose levels decrease the intermediates needed to utilize ketone bodies (A)</p> Signup and view all the answers

What is the role of insulin in regulating blood glucose levels?

<p>Insulin signals cells to absorb glucose for energy. (C)</p> Signup and view all the answers

What is one major function of fats in the body?

<p>Cushioning organs and providing insulation (A)</p> Signup and view all the answers

Which of the following statements about fatty acids is true?

<p>Fatty acids can vary in length and saturation (B)</p> Signup and view all the answers

How many calories do fats provide per gram?

<p>9 kcal (D)</p> Signup and view all the answers

Which of the following is NOT a role of fats in the human body?

<p>Directly transporting oxygen in the bloodstream (D)</p> Signup and view all the answers

Which types of fatty acids are essential for health?

<p>Omega-3 and omega-6 fatty acids (A)</p> Signup and view all the answers

What component is primarily responsible for storing fats in the body?

<p>Adipocytes (C)</p> Signup and view all the answers

Which hormone is primarily secreted during physical activity to mobilize energy?

<p>Epinephrine (B)</p> Signup and view all the answers

What is the correct order of the enzymatic steps involved in the mobilization of TAGs?

<p>TAG → DAG → MAG → Glycerol + FFAs (A)</p> Signup and view all the answers

What role does glucagon play in fat metabolism?

<p>Promoting energy availability during fasting (D)</p> Signup and view all the answers

What is the main function of lipase in fat digestion?

<p>Hydrolyzing triacylglycerol (B)</p> Signup and view all the answers

In what context does insulin inhibit lipolysis most effectively?

<p>After meals (B)</p> Signup and view all the answers

Which of these substances contributes to fat absorption in the intestine?

<p>Bile salts (C)</p> Signup and view all the answers

During which condition is triacylglycerol mobilization most crucial?

<p>Physical stress or fasting (D)</p> Signup and view all the answers

Which hormone is primarily released during fasting or low blood glucose levels?

<p>Glucagon (B)</p> Signup and view all the answers

What is the role of cyclic AMP (cAMP) in lipolysis?

<p>It acts as a second messenger activating protein kinase A (PKA). (A)</p> Signup and view all the answers

Which enzyme hydrolyzes triglycerides (TAGs) into diacylglycerols (DAGs) and free fatty acids (FFAs)?

<p>Adipose triglyceride lipase (ATGL) (B)</p> Signup and view all the answers

What is the first step in the oxidation of fatty acids?

<p>Conversion to fatty acyl-coenzyme A (CoA) (C)</p> Signup and view all the answers

What is the function of perilipin in the lipolysis process?

<p>It restructures lipid droplets to expose TAGs to lipases. (A)</p> Signup and view all the answers

Which of the following describes the transport process of free fatty acids (FFAs) after lipolysis?

<p>FFAs bind to albumin for transport in the bloodstream. (C)</p> Signup and view all the answers

What is the primary enzyme activated by cAMP during lipolysis?

<p>Hormone-sensitive lipase (HSL) (C)</p> Signup and view all the answers

What is the outcome of monoacylglycerol lipase (MAGL) activity during lipolysis?

<p>It produces glycerol and free fatty acids. (B)</p> Signup and view all the answers

Flashcards

What are lipids?

A type of lipid that includes fats, oils, waxes, phospholipids and steroids.

What are the functions of fats in our bodies?

Fats are important as carriers of other nutrients (like vitamins) and contribute to the flavor of our food. However, their consumption should be monitored due to their high energy content.

What is the primary function of fats in our bodies?

Fats are a concentrated source of energy, providing 9 kcal per gram, making them efficient energy storage molecules in our body.

What is the general structure of a fatty acid?

Fatty acids are long chains of carbon atoms with a carboxylic acid group at one end. The length and saturation of these chains varies.

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What are the main functions of fatty acids?

Fatty acids play crucial roles in energy storage, cell membrane structure, and signaling processes within the body.

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Fatty Acid

A long-chain carboxylic acid with a hydrocarbon chain attached to a carboxyl group (COOH). They provide energy and are building blocks for cell membranes and signaling molecules.

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Saturated Fatty Acid

Fatty acids with only single bonds between carbon atoms. Tend to be solid at room temperature and found in animal fats.

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Unsaturated Fatty Acid

Fatty acids with one or more double bonds between carbon atoms. Tend to be liquid at room temperature and found in plant oils.

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Fat Mobilization

The breaking down of fat into smaller molecules for energy.

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Lipase

A pancreatic enzyme that breaks down triacylglycerols into fatty acids and glycerol by binding to the lipid-water interface and hydrolyzing ester bonds.

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Glucagon

A hormone released during fasting or low blood sugar to stimulate fat breakdown (lipolysis) and increase blood glucose.

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Epinephrine (Adrenaline)

A hormone released during stress or physical activity to stimulate the rapid release of energy from fat stores.

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Insulin

A hormone released after meals to inhibit fat breakdown and promote fat storage.

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Lipolysis

The process of breaking down stored fat (triglycerides) into free fatty acids (FFAs) and glycerol, releasing them into the bloodstream for energy use.

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Triggering Hormones in Lipolysis

Hormones that trigger the release of stored energy, like during stress or fasting. Examples include adrenaline and glucagon.

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Hormone Receptors in Lipolysis

Specialized proteins on the surface of fat cells (adipocytes) that bind to specific hormones, initiating the lipolysis cascade.

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G Protein (Gs protein) in Lipolysis

A protein that activates adenylyl cyclase, a key enzyme involved in lipolysis.

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Adenylyl Cyclase in Lipolysis

An enzyme that converts ATP to cyclic AMP (cAMP), an important second messenger in lipolysis.

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Cyclic AMP (cAMP) in Lipolysis

A second messenger that activates Protein Kinase A (PKA), crucial for lipolysis.

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Protein Kinase A (PKA) in Lipolysis

An enzyme activated by cAMP that phosphorylates target proteins, including those involved in fat breakdown.

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Lipolysis Initiation

The process where enzymes break down triglycerides into their components: fatty acids and glycerol. These components are then released into the bloodstream for energy use.

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What is β-oxidation?

A process that converts fatty acids into energy in the mitochondria, involving a series of steps that break down the fatty acid molecule.

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What is carnitine?

A molecule that carries activated fatty acids into the mitochondria for energy production.

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What is gluconeogenesis?

The process of converting non-carbohydrate sources, like amino acids and glycerol, into glucose in the liver.

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What are ketone bodies?

Substances produced by the liver during gluconeogenesis that can be used as an alternative energy source by the body, especially during fasting or starvation.

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How are fatty acids activated?

The activation of a fatty acid molecule by attaching it to coenzyme A, requiring energy from ATP.

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What is carnitine acyltransferase?

The specific enzyme that catalyzes the entry of activated fatty acids into the mitochondria, using carnitine as a carrier.

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What is the role of coenzyme A (CoA) in fatty acid metabolism?

Coenzyme A (CoA) is a molecule essential for the activation and transport of fatty acids within the cell.

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What is ketosis?

A state of energy deficiency caused by low glucose levels, often during prolonged fasting or starvation, where the body starts utilizing alternative energy sources like ketone bodies.

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How are ketone bodies produced?

Ketone bodies are produced when the body breaks down fat for energy, especially during fasting, exercise, starvation, or in the case of type 1 diabetes.

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What is the role of ketone bodies in starvation?

The brain prefers glucose for energy, but can use ketone bodies after about four days of starvation. This allows the body to function without food for longer periods.

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What are the risks of high ketone body levels?

If ketone bodies build up too quickly, they can overwhelm the kidneys and lead to ketoacidosis, a dangerous condition.

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How do keto diets work?

Keto diets aim to induce ketosis by drastically reducing carbohydrates, forcing the body to rely on fat for energy.

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How are ketone bodies related to type 1 diabetes?

In type 1 diabetes, the body can't produce insulin, so glucose can't enter cells for energy. The body then switches to using fat, leading to increased ketone body production.

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What is the role of the liver in diabetes and ketone body production?

The liver produces ketone bodies to compensate for the lack of glucose in cells in people with diabetes.

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How are ketone bodies eliminated from the body?

Ketone bodies are removed primarily by the kidneys, but their capacity is limited, so excessive production can lead to ketoacidosis.

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Study Notes

Fatty Acid Catabolism

  • Fats are crucial components of many bodily tissues and important for carrying other nutrients, including vitamins. Fat consumption should be monitored.
  • Lipids include phospholipids, triglycerides, and cholesterol, contributing to cell membrane structure.
  • Fats in the diet provide energy (9 kcal per gram), insulate and protect organs, and are essential for absorbing fat-soluble vitamins (A, D, E, K).
  • Sources of dietary fat include eggs, avocados, sardines, pistachios, walnuts, almonds, olive oil, and nut butter.

Contents of Fatty Acid Catabolism

  • Introduction to fatty acids
  • Digestion, mobilization, and transport of fats
  • Oxidation of fatty acids
  • Ketone bodies

Introduction to Fatty Acids

  • Fats are composed of carbon, hydrogen, and oxygen.
  • A fat molecule includes glycerol with attached fatty-acid chains.
  • Different types of fats have various fatty acids bound to glycerol.

Classification of Fatty Acids

  • Saturated: No double bonds, solid at room temperature (e.g., butyric acid, palmitoleic acid, stearic acid).
  • Unsaturated: One or more double bonds;
    • Essential: Omega-3 (e.g. α-linolenic acid), ω-6 (e.g. linoleic acid), EPA, and DHA.
    • Non-essential: ω-9 (e.g. Oleic acid), GLA.

Digestion, Mobilization, and Transport of Fats

  • Dietary triacylglycerols are a significant energy source, contributing about one-third of energy requirements.
  • The liver and heart utilize fatty acids for roughly 80% of their energy needs.
  • Hibernating animals often rely almost exclusively on fat reserves for sustained energy (and water) during long periods of dormancy.

Hormonal Trigger Mobilization of Stored Triacylglycerols

  • Hydrolysis of TAGs is catalyzed by lipases, generating MAGs, DAGs, FFAs, and glycerol.
  • Lipases are regulated by hormones like epinephrine ("we need energy now") and glucagon ("we're out of glucose").

Mechanism of TAG Mobilization

  • Step 1: Hormonal activation. Epinephrine/adrenaline (during stress/exercise), and glucagon (during fasting/low blood glucose).
  • Step 2: Activation of Adenylyl Cyclase. Hormone-receptor interaction activates G-protein (specifically Gs protein), which stimulates adenylyl cyclase. This enzyme converts ATP to cyclic AMP (cAMP).
  • Step 3: Activation of Protein Kinase A (PKA). cAMP activates PKA, which phosphorylates target proteins, initiating lipolysis. Hormone-sensitive lipase (HSL) and perilipin are targeted proteins.
  • Step 4: Lipolysis Initiation. Perilipin phosphorylation restructures the lipid droplet, causing TAGs to become exposed to lipases. Adipocyte triglyceride lipase (ATGL) breaks down TAGs into free fatty acids (FFAs) and diacylglycerol. Hormone-sensitive lipase (HSL) further breaks down diacylglycerol to MAGs and FFAs. Monoacylglycerol lipase (MAGL) converts MAG to glycerol.
  • Step 5: Release of Products. Free fatty acids (FFAs) are released into the bloodstream, bound to albumin, and taken up by muscle and liver tissues for beta-oxidation and ATP production. Glycerol is transported to the liver and used in gluconeogenesis or glycolysis.

Fat Transport into Mitochondria

  • Fatty acids are transported or pass into mitochondria. Smaller fatty acids (less than 12 carbons) diffuse freely. Larger fatty acids are transported using a carnitine shuttle, which utilizes carnitine acyltransferase I in the cytosol and carnitine acyltransferase II in the mitochondria.

Conversion of Fatty Acid to Fatty Acyl-CoA

  • Fatty acids are activated and converted to fatty acyl-CoA by acyl-CoA synthetase. This process requires ATP.

IV. Oxidation of Fatty Acids

  • Fatty acid oxidation occurs in the mitochondrial matrix.
  • The process breaks down fatty acids into two-carbon acetyl-CoA units.
  • Oxidative conversion involves four steps or stages in each cycle to produce NADH, FADHâ‚‚ and acetyl-CoA.
  • Acetyl-CoA then enters the citric acid cycle.
  • The final two steps use the electron transport chain to get ATP from NADH and FADH2

V. Ketone Bodies

  • Ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) are produced by the liver during gluconeogenesis, when glucose supply is low or absent.
  • They are used by the body for energy, particularly by the brain during fasting or starvation.
  • The production and usage of ketone bodies are tightly regulated and influenced by dietary intake, metabolic states (like exercise and diabetes), and more.
  • Untreated diabetes may cause a build-up of ketone bodies, leading to ketoacidosis, a potentially serious condition.

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Fatty Acid Catabolism - Biochemistry II PDF

Description

This quiz covers the fundamentals of fatty acid catabolism, including digestion, mobilization, and oxidation of fats. Learn about the importance of dietary fats and their role in energy storage and nutrient transport. Explore the various types of fatty acids and their physiological significance.

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