Beta Oxidation and Fatty Acids

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Questions and Answers

What is the primary product of beta oxidation of fatty acids?

Acetyl CoA (correct)

Fatty Acid Binding Protein

Glycerol

Glucose

Which of the following fatty acids is classified as short-chain?

Butyric acid (correct)

Palmitic acid

Stearic acid

Linoleic acid

Which fatty acid is a polyunsaturated fat and cannot be synthesized by mammals?

Arachidonic acid (correct)

Oleic acid

Stearic acid

Palmitic acid

Essential fatty acids for mammals include which of the following?

Linoleate Signup and view all the answers

Which fatty acid is identified by the systematic name octadecanoic acid?

Stearic acid Signup and view all the answers

Why are long chain fatty acids not soluble in water?

They consist of large hydrophobic chains. Signup and view all the answers

Which fatty acid has the trivial name cis-9-octadecenoic?

Oleic acid Signup and view all the answers

What type of fatty acids are transported in the blood complexed with albumin?

Long-chain fatty acids Signup and view all the answers

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

It activates fatty acids by esterifying them to CoA. Signup and view all the answers

Which enzyme is responsible for the dehydrogenation step in β-oxidation?

Acyl CoA dehydrogenase Signup and view all the answers

What triggers the activation of fatty acids for degradation or synthesis?

Esterification with CoA Signup and view all the answers

Which of the following is true about the ATP requirement in fatty acid activation?

It is needed because the process is ATP-dependent. Signup and view all the answers

What type of reaction occurs between the α and β carbons during dehydrogenation?

An oxidative reaction Signup and view all the answers

How many specific types of Acyl CoA dehydrogenases are mentioned for different acyl chain lengths?

Three Signup and view all the answers

What does MCAD deficiency primarily affect?

The metabolism of medium-chain fatty acids Signup and view all the answers

What is produced during the second dehydrogenation of β-oxidation?

NADH Signup and view all the answers

Which process occurs after dehydrogenation in β-oxidation?

Hydration of the double bond Signup and view all the answers

What enzyme catalyzes the thiolytic cleavage in β-oxidation?

β-ketoacyl CoA thiolase Signup and view all the answers

What is the final product of β-oxidation for fatty acids with odd numbers of carbon atoms?

Acetyl-CoA and 1 mol of propionyl-CoA Signup and view all the answers

How many ATPs are produced from the oxidation of FADH2 in the electron transport chain?

2 ATPs Signup and view all the answers

What condition can result from carnitine deficiency?

Muscle cramps with fasting Signup and view all the answers

What is the role of NAD+ dependent hydrogenase in β-oxidation?

Convert L-β-hydroxy acyl CoA to β-keto acyl-CoA Signup and view all the answers

What is the initial reaction in the β-oxidation pathway?

Oxidation of a fatty acyl CoA Signup and view all the answers

What issue is associated with carnitine deficiency in preterm infants?

Impaired fatty acid oxidation Signup and view all the answers

What is produced in each round of β-oxidation?

One molecule of FADH2 and one molecule of NADH+H+ Signup and view all the answers

What is the final product of β-oxidation of odd chain fatty acids?

Succinyl-CoA Signup and view all the answers

Which enzyme is responsible for converting D-methylmalonyl-CoA to L-methylmalonyl-CoA?

Methylmalonyl-CoA epimerase Signup and view all the answers

What is the effect of cis-Δ3-Enoyl CoA isomerase in unsaturated fatty acid β-oxidation?

It converts cis-Δ3 bonds to trans-Δ2 bonds Signup and view all the answers

What is the first step in fatty acid synthesis?

Carboxylation of Acetyl CoA Signup and view all the answers

Which coenzyme is required by methylmalonyl-CoA mutase?

Vitamin B12 Signup and view all the answers

Which enzyme is the rate-limiting enzyme in fatty acid synthesis?

Acetyl CoA carboxylase Signup and view all the answers

How many β-oxidation cycles occur for a fatty acid with 18 carbons?

8 Signup and view all the answers

What regulates the acetyl CoA carboxylase enzyme allosterically?

Citrate and palmitoyl CoA Signup and view all the answers

What happens to an acyl CoA containing a cis-Δ4 double bond?

It forms a 2,4-dienoyl intermediate Signup and view all the answers

During which step is CO2 lost in fatty acid synthesis?

Step 3: Condensation Signup and view all the answers

Which fatty acid processing occurs similarly for both odd and even chain fatty acids until the final cleavage?

β-Oxidation Signup and view all the answers

What does the malonyl transacylase enzyme transfer to the SH group?

Malonyl group Signup and view all the answers

What is produced after the reduction of acetoacetyl ACP?

Beta-hydroxy fatty acyl ACP Signup and view all the answers

Which enzyme catalyzes the condensation of acetyl and malonyl units?

Condensing enzyme Signup and view all the answers

What is formed after the second reduction in fatty acid synthesis?

Butyryl ACP Signup and view all the answers

Study Notes

Beta Oxidation

Beta oxidation is the process in which fatty acids are broken down into acetyl CoA.
Acetyl CoA enters the TCA cycle to produce energy.
Fatty acids are categorized by the length of their carbon chain:
- Very long chain fatty acids: >20 carbons
- Long chain fatty acids: C12-C20
- Medium chain fatty acids: C6-C12
- Short chain fatty acids: C4

Fatty Acid Transport

Fatty acids are not soluble in water.
Fatty acids are transported in the blood by complexing with albumin.
Inside cells, fatty acids are attached to fatty acid binding protein (FABP).

Key Fatty Acids

Palmitic acid (16:0): Hexadecanoic acid, a saturated fatty acid.
Palmitoleic acid (16:1): cis-9-hexadecenoic acid, a monounsaturated fatty acid.
Stearic acid (18:0): Octadecanoic acid, a saturated fatty acid.
Oleic acid (18:1): cis-9-octadecenoic acid, a monounsaturated fatty acid.
Linoleic acid (18:2): cis,cis-9,12 octadecenoic acid, a polyunsaturated fatty acid.
Linolenic acid (18:3): cis,cis,cis-9,12,15-octadecatrienoic acid, a polyunsaturated fatty acid.
Arachidonic acid (20:4): cis,cis,cis,cis-5,8,11,14-eicosatetraenoic acid, a polyunsaturated fatty acid.

Essential Fatty Acids

Mammals lack the enzymes to introduce double bonds beyond carbon 9 in the fatty acid chain.
Mammals cannot synthesize linoleate, linolenate, and arachidonate.
These three fatty acids are called essential fatty acids.

Fatty Acid Activation

Fatty acids must be esterified to Coenzyme A before they can be metabolized.
Acyl-CoA Synthases (Thiokinases) catalyze the activation of long-chain fatty acids.
This process is ATP-dependent and occurs in two steps.
Different Acyl-CoA Synthases exist for fatty acids of different chain lengths.

Beta-Oxidation

Beta-oxidation is a four-step process that occurs in the mitochondria.

Beta-Oxidation Steps

1) Dehydrogenation: FAD-linked reaction catalyzed by Acyl-CoA dehydrogenase leading to a trans-double bond.
- Long chain fatty acyl CoA dehydrogenase (LCAD) acts on chains greater than C12.
- Medium chain fatty acyl CoA dehydrogenase (MCAD) acts on chains of C6 to C12.
- Short chain fatty acyl CoA dehydrogenase (SCAD) acts on chains of C4 to C6.
2) Hydration: Hydration of the double bond is catalyzed by Enoyl-CoA hydratase, yielding L-3-hydroxyacyl-CoA and 1 NADH.
3) 2nd Dehydrogenation: NAD-linked reaction catalyzed by β-hydroxyacyl-CoA dehydrogenase leading to a ketone.
4) Thiolytic Cleavage: Thiolytic cleavage of the thioester is catalyzed by β-ketoacyl-CoA thiolase, yielding 1 acetyl-CoA and a shortened fatty acid (acyl-CoA).

Beta-Oxidation Outcomes

Each round of β-oxidation yields 1 FADH2, 1 NADH, and 1 acetyl-CoA.
The cycle repeats shortening the fatty acid by 2 carbons until it is completely broken down into acetyl-CoA.
Odd-numbered carbon fatty acids produce propionyl-CoA in the last round.
Odd-chain fatty acids are less common and require specific enzymes for further metabolism.

Carnitine Deficiency

Deficiency of the carnitine translocase can lead to defects in long-chain fatty acid transport.
This condition can cause muscle cramps, especially during fasting, exercise, or high-fat diets.
Carnitine deficiency is reported in preterm infants, resulting in impaired fatty acid oxidation and hypoglycemia.

Clinical Application of Beta-Oxidation

Beta-oxidation is essential for energy production from fatty acids.
Defects in this process can lead to various metabolic disorders.

Fatty Acid Synthase Complex

This complex is important for building fatty acids.
Several enzymes work together to complete fatty acid synthesis.
The thio-esterase is involved in releasing the palmitate synthesized.

Steps in Fatty Acid Synthesis

Step 1: Carboxylation of Acetyl-CoA: Acetyl CoA is carboxylated to form malonyl CoA by acetyl CoA carboxylase, a rate-limiting enzyme.
Step 2: Transfer to FAS: Acetyl CoA and malonyl CoA bind to the fatty acid synthase complex.
- Acetyl transacylase transfers acetyl groups to the condensing enzyme (CE).
- Malonyl transacylase transfers malonyl groups to the ACP (acyl carrier protein).
Step 3: Condensation: Condensation of acetyl and malonyl units to form β-ketoacyl-ACP, releasing CO2.
Step 4: Reduction: β-ketoacyl-ACP is reduced by NADPH-dependent β-ketoacyl reductase to form β-hydroxy fatty acyl-ACP.
Step 5: Dehydration: β-hydroxy fatty acyl-ACP is dehydrated by a dehydratase to form enoyl-ACP.
Step 6: 2nd Reduction: Enoyl-ACP is reduced by enoyl reductase (ER) using NADPH to form butyryl-ACP.

Cyclical Reactions Of Fatty Acid Synthesis

The cycle continues until the desired fatty acid length is reached.
Repeated cycles elongate the fatty acid chain by two carbons.
Fatty acids are then released and used as building blocks for other molecules.

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Description

This quiz explores the essential concepts of beta oxidation, fatty acid transport, and key fatty acids. You'll learn about the breakdown of fatty acids into acetyl CoA, their categorization by carbon chain length, and their transport in the bloodstream. Test your knowledge on different types of fatty acids and their significance in energy metabolism.