Biochemistry Chapter 14: Fat as Fuel

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Questions and Answers

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

Production of a fatty acyl-CoA with 2 fewer carbons and acetyl-CoA (correct)

Production of a fatty acyl-CoA with 4 fewer carbons and 2 acetyl-CoA

Production of a fatty acyl-CoA with 4 more carbons

Production of a fatty acyl-CoA with 2 more carbons

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

To generate ATP from fatty acid oxidation

To facilitate the transport of fatty acids across the inner mitochondrial membrane (correct)

To convert fatty acyl-CoA into acetyl-CoA

To catalyze the β-oxidation reaction

What is the enzyme responsible for transferring the fatty acid group to carnitine?

Acetyl-CoA carboxylase

Carnitine acyltransferase I (correct)

Fatty acyl-CoA synthase

Carnitine acyltransferase II

What is the name of the process by which fatty acids are transported into mitochondria?

Transport of fatty acids into mitochondria (D) Signup and view all the answers

What is the reason why the β-carbon undergoes oxidation in β-oxidation?

To form a carbonyl group (D) Signup and view all the answers

What is the net result of the reaction catalyzed by carnitine acyltransferase II?

Recreation of fatty acyl-CoA (B) Signup and view all the answers

What is the primary function of adipose tissue lipase?

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

What is the purpose of the carnitine shuttle system?

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

What are the byproducts of the β-oxidation pathway?

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

What is the significance of ketogenesis in starvation?

It provides energy for the brain and other organs (D) Signup and view all the answers

What is the function of phospholipids in cell membranes?

To form the lipid bilayer of cell membranes (C) Signup and view all the answers

Why can't the liver utilise ketone bodies?

Because it is the main organ responsible for producing ketone bodies (C) Signup and view all the answers

What is the role of cholesterol in lipid metabolism?

To serve as a precursor for steroid hormones (B) Signup and view all the answers

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

Glucose (C) Signup and view all the answers

What is the function of arachidonic acid in lipid metabolism?

To serve as a precursor for prostaglandins (C) Signup and view all the answers

What is the primary destination of acetoacetate and β-hydroxybutyrate in the bloodstream?

Most tissues for energy production (A) Signup and view all the answers

What is the importance of triglyceride fat for long-term fuel storage?

It provides a long-term energy reserve during periods of fasting or starvation (D) Signup and view all the answers

Why can't the brain utilise fatty acids as a primary source of energy?

Because fatty acids cannot cross the blood-brain barrier (B) Signup and view all the answers

What is the primary function of ketone bodies in the brain?

Emergency fuel during times of low glucose availability (C) Signup and view all the answers

What is the product of the conversion of propionyl-CoA in the metabolism of fatty acids?

Succinyl-CoA (C) Signup and view all the answers

What is the primary function of acetyl-CoA in the metabolism of fatty acids?

Entry point into the citric acid cycle (A) Signup and view all the answers

What is the primary reason why ketone bodies are produced in the liver?

To provide energy for other tissues during times of low glucose availability (C) Signup and view all the answers

What is the approximate amount of fat stored in a 70 kg adult?

11 kg (A) Signup and view all the answers

What is the energy yield per gram of fat?

38 kJ (A) Signup and view all the answers

What is the function of lipase in adipose tissue?

Breaking down triglycerides into fatty acids and glycerol (B) Signup and view all the answers

What is the primary role of glycerol in metabolism?

Entering glycolysis and being converted to glucose or pyruvate (B) Signup and view all the answers

What is the primary location of fatty acid β-oxidation?

Mitochondrial matrix (A) Signup and view all the answers

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

Forming thioester bonds with carboxylic acids (B) Signup and view all the answers

What is the purpose of the carnitine shuttle?

Transporting fatty acyl-CoA into mitochondria (A) Signup and view all the answers

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

Removal of 2 hydrogen atoms (C) Signup and view all the answers

What is the energy yield per gram of protein?

21 kJ (C) Signup and view all the answers

What is the role of the carnitine shuttle in fat metabolism?

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

What is the approximate amount of glucose stored in the liver of a 70 kg adult?

10 g (C) Signup and view all the answers

What is the energy yield from the complete oxidation of one molecule of fatty acid with 16 carbon atoms?

107 ATP (B) Signup and view all the answers

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

Acetyl-CoA (C) Signup and view all the answers

What is the enzyme responsible for the removal of 2 hydrogens in Reaction 3 of the β-oxidation pathway?

Hydroxyacyl-CoA dehydrogenase (D) Signup and view all the answers

What is the fate of the last 3 carbons in the metabolism of odd-numbered fatty acids?

They are converted to propionyl-CoA (C) Signup and view all the answers

What is the condition under which ketone body formation occurs?

When fat metabolism is the main source of energy (D) Signup and view all the answers

What is the role of FAD in the β-oxidation pathway?

To accept electrons during the oxidation of fatty acyl-CoA (A) Signup and view all the answers

How many repeats of the β-oxidation pathway are required for the complete oxidation of a fatty acid with 16 carbon atoms?

7 repeats (B) Signup and view all the answers

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

Removal of 2 carbon units (C) 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 - triglycerides stored as large fat droplets in adipose tissue
Large body stores - 70 kg adult has 11 kg fat (as TG) and 120 g glycogen in liver
Efficiency on weight basis - 1 g fat yields 38 kJ, 1 g protein yields 21 kJ, and 1 g carbohydrate yields 17 kJ

Structure of Triglyceride Fat

Triglyceride fat (triacylglycerols) composed of glycerol and three fatty acids
Common fatty acids: palmitic acid (C 16:0), stearic acid (C 18:0), oleic acid (C 18:1), and linoleic acid (C 18:2)

Breakdown of Stored Triglyceride Fat

Lipase breaks down triglyceride fat into fatty acids and glycerol
Adrenaline and glucagon activate lipase
Fatty acids travel in plasma bound to albumin
Glycerol diffuses in blood stream to all tissues

Metabolism of Glycerol

Glycerol is water soluble and taken up by all tissues
Enters glycolysis pathway for conversion to pyruvate, then into TCA cycle for oxidation to CO2

Fatty Acid Metabolism by β-Oxidation Pathway

All reactions occur in the mitochondrial matrix
Intermediates present as CoA thioesters
Biological energy of fatty acid molecule conserved as transfer of 2 H atoms to cofactors NAD+ and FAD
Series of four enzyme reactions results in removal of two carbon units as acetyl CoA

Activation of Long Chain Fatty Acids

Fatty acyl-CoA synthetase in cytosol adds CoA to fatty acid
Coenzyme A forms thioester bonds with carboxylic acids

Transport of Fatty Acyl-CoA into Mitochondria

Carnitine shuttle system transports fatty acyl-CoA into mitochondria
Two stages: Stage 1 - Fatty acyl-CoA diffuses across the outer mitochondrial membrane, and Stage 2 - Carnitine is switched back for CoA by carnitine acyltransferase II

β-Oxidation Pathway

Overview: Fatty acyl-CoA with 10 carbons undergoes β-oxidation producing acetyl-CoA and a fatty acyl-CoA that is 2 carbons shorter
One round of β-oxidation produces acetyl-CoA and a fatty acyl-CoA that is 2 carbons shorter
Four reactions: 1) Removal of 2 H atoms, 2) Addition of water, 3) Removal of 2 H atoms, and 4) Removal of 2 C units

Regulation of Fat Metabolism

Release of fatty acids from adipose tissue activated by adrenaline and glucagon
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-carboxylase converts propionyl-CoA to methylmalonyl-CoA
Methylmalonyl-CoA mutase converts methylmalonyl-CoA to succinyl-CoA

Ketone Body Formation

Ketogenesis occurs when fat metabolism is the main source of energy
Fatty acid oxidation in hepatocytes leads to high concentrations of Acetyl CoA - exceeds capacity of the TCA cycle
Excess Acetyl CoA is converted into ketone bodies (acetoacetate and β hydroxybutyrate) in liver
Ketone bodies can be utilised for energy by most tissues

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Description

This quiz covers the topic of fat as fuel in biochemistry and molecular biology, specifically chapter 14. It assesses understanding of the role of fat in metabolic processes.