Biochemistry Chapter 14: Fat as Fuel

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of carnitine acyltransferase I in the transport of fatty acids into mitochondria?

To transfer the fatty acid group to carnitine, creating fatty acyl-carnitine (correct)

To recreate fatty acyl-CoA from fatty acyl-carnitine

To oxidize the β-carbon, producing a carbonyl group

To facilitate the crossing of fatty acyl-carnitine into the inner mitochondrial membrane

What is the net result of one round of β-oxidation?

The production of acetyl-CoA and a fatty acyl-CoA that is 4 carbons shorter

The production of acetyl-CoA and a fatty acyl-CoA that is 3 carbons shorter

The production of acetyl-CoA and a fatty acyl-CoA that is 2 carbons shorter (correct)

The production of acetyl-CoA and a fatty acyl-CoA that is 1 carbon shorter

What is the purpose of the translocase in the transport of fatty acids into mitochondria?

To oxidize the β-carbon, producing a carbonyl group

To transfer the fatty acid group to carnitine, creating fatty acyl-carnitine

To facilitate the crossing of fatty acyl-carnitine into the inner mitochondrial membrane (correct)

To recreate fatty acyl-CoA from fatty acyl-carnitine

What is the function of carnitine acyltransferase II in the transport of fatty acids into mitochondria?

To recreate fatty acyl-CoA from fatty acyl-carnitine Signup and view all the answers

What is the name of the process by which fatty acids are broken down in the mitochondria?

β-oxidation Signup and view all the answers

Why is the process of β-oxidation called as such?

Because it involves the oxidation of the β-carbon Signup and view all the answers

What is the primary function of adipose tissue lipase?

To break down triglycerides into fatty acids and glycerol Signup and view all the answers

What is the purpose of the carnitine shuttle system?

To transport fatty acids from the cytosol to the mitochondria Signup and view all the answers

What is the end product of the β-oxidation pathway?

Acetyl-CoA, NADH, and FADH2 Signup and view all the answers

What is the significance of ketogenesis in starvation?

It provides a alternative source of energy during starvation Signup and view all the answers

What is the role of cholesterol in the biological functions of lipids?

It is a precursor to steroid hormones Signup and view all the answers

What is the function of arachidonic acid in the biological functions of lipids?

It is a precursor to prostaglandins Signup and view all the answers

What is the primary function of triglycerides in the body?

To store energy for long-term use Signup and view all the answers

What is the role of fatty acids in the biological functions of lipids?

They are activated to their CoA esters and transported into the mitochondria Signup and view all the answers

What is the approximate energy yield of 1 gram of fat?

38 kJ Signup and view all the answers

Which of the following is NOT a common fatty acid?

Glutamic acid Signup and view all the answers

What is the byproduct of the breakdown of triglycerides in adipose tissue?

Fatty acids and glycerol Signup and view all the answers

In which tissue is glycerol primarily taken up and converted to glucose?

Liver Signup and view all the answers

What is the primary function of the carnitine shuttle?

To transport fatty acids into the mitochondria Signup and view all the answers

What is the net result of the beta-oxidation pathway?

The breakdown of fatty acids into acetyl-CoA Signup and view all the answers

What is the byproduct of the activation of long-chain fatty acids?

AMP and PPi Signup and view all the answers

What is the function of CoA-SH in the activation of fatty acids?

To form a thioester bond with the fatty acid Signup and view all the answers

What is the primary advantage of storing energy as triglycerides?

They are more compactly stored Signup and view all the answers

What is the role of lipase in the breakdown of triglycerides?

To break down triglycerides into fatty acids and glycerol Signup and view all the answers

What is the result of Reaction 1 in the β-oxidation pathway?

Removal of 2 hydrogens and cleavage of a bond Signup and view all the answers

What is the purpose of the carnitine shuttle?

To transport fatty acids into the mitochondria Signup and view all the answers

What is the ATP yield from the complete oxidation of a fatty acid with 16 carbon atoms?

107 ATP Signup and view all the answers

What is the end product of β-oxidation that enters the TCA cycle?

Acetyl-CoA Signup and view all the answers

What is the purpose of the electron transport chain in β-oxidation?

To reoxidize NADH and FADH2 Signup and view all the answers

What is the fate of the last 3 carbons of an odd-numbered fatty acid?

They are converted to methylmalonyl-CoA Signup and view all the answers

What is the purpose of the enzyme Propionyl-CoA-carboxylase?

To convert propionyl-CoA to methylmalonyl-CoA Signup and view all the answers

What is the condition under which ketogenesis occurs?

When the TCA cycle is overloaded with acetyl-CoA Signup and view all the answers

What is the result of Reaction 4 in the β-oxidation pathway?

Removal of 2 carbon units and the formation of acetyl-CoA Signup and view all the answers

What is the purpose of the enzyme enoyl-CoA hydratase?

To convert enoyl-CoA to hydroxyacyl-CoA Signup and view all the answers

What is the primary destination of acetoacetate and β hydroxybutyrate released from the liver?

Bloodstream Signup and view all the answers

Why can't the liver utilize ketone bodies?

It is specialized to produce ketone bodies, not utilize them Signup and view all the answers

What is the primary source of energy for red blood cells?

Glucose Signup and view all the answers

What is the fate of acetoacetate and β hydroxybutyrate in most tissue cells?

They are converted back to TCA cycle intermediates Signup and view all the answers

What is the role of ketone bodies in the brain?

Emergency fuel source Signup and view all the answers

What is the fate of excess acetyl-CoA in the liver?

It is converted to ketone bodies Signup and view all the answers

Which of the following tissues can utilize both fatty acids and ketone bodies for energy?

Most tissue cells Signup and view all the answers

What is the primary reason why the brain cannot utilize fatty acids for energy?

Inability to cross the blood-brain barrier Signup and view all the answers

Study Notes

Biological Functions of Lipids

Components of cell membranes (phospholipids and cholesterol)
Precursors of hormones (cholesterol and arachidonic acid)
Long-term fuels (triglycerides)

Efficiency of Triglycerides as Fuel

Compact storage: large fat droplets in adipose tissue cells
Large body stores: 11 kg fat (as triglycerides) in a 70 kg adult
Efficiency on weight basis: 1 g fat yields 38 kJ, compared to 1 g protein (21 kJ) and 1 g carbohydrate (17 kJ)

Structure of Triglyceride Fat

Glycerol component of triacylglycerol
Common fatty acids: palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), and linoleic acid (C18:2)

Breakdown of Stored Triglyceride Fat in Adipose Tissue

Lipase (activated by adrenaline and glucagon) breaks down triglyceride into fatty acids and glycerol
Fatty acids travel in the plasma bound to albumin
Glycerol diffuses into the bloodstream and is taken up by the liver for glycolysis

Metabolism of Glycerol

Glycerol is water-soluble and taken up by all tissues
In liver, glycerol enters glycolysis and is converted to pyruvate, then into the TCA cycle for oxidation

Fatty Acid Metabolism by β-Oxidation Pathway

Occurs in the mitochondrial matrix
Biological energy of fatty acid molecule is conserved as the transfer of 2 H atoms to the cofactors NAD+ and FAD
Series of four enzyme reactions result in the removal of a 2-carbon unit as acetyl CoA

Activation of Long-Chain Fatty Acids

Fatty acyl-CoA synthetase catalyzes the reaction between fatty acids and CoA
Forms a thioester bond between the fatty acid and CoA

Transport of Fatty Acyl-CoA into Mitochondria: Carnitine Shuttle

Fatty acyl-CoA is converted into fatty acyl-carnitine, which crosses the inner mitochondrial membrane via a translocase
Carnitine is switched back for CoA by carnitine acyltransferase II

β-Oxidation Pathway

Fatty acyl-CoA with 10 carbons undergoes β-oxidation
One round of β-oxidation produces acetyl CoA and a fatty acyl-CoA that is 2 carbons shorter
The process is energetically neutral

Regulation of Fat Metabolism

Release of fatty acids from adipose tissue (adrenaline and glucagon activate lipase enzyme)
Rate of entry into mitochondria via carnitine shuttle
Rate of reoxidation of cofactors NADH and FADH2 by Electron Transport Chain

Metabolism of Odd-Numbered Fatty Acids

β-Oxidation results in the production of propionyl-CoA
Propionyl-CoA is converted into succinyl-CoA, which enters the TCA cycle

Ketone Body Formation

Occurs when fat metabolism is the main source of energy (starvation, Type I diabetes)
Fatty acid oxidation in hepatocytes leads to high concentrations of Acetyl CoA, which is converted into ketone bodies (acetoacetate and β-hydroxybutyrate) in the liver
Ketone bodies can be utilized for energy by most tissues, but not the liver

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about the role of fat as fuel in biochemistry and molecular biology. This lecture covers the basics of fat metabolism and its importance in nutrition.