Biochem Fatty Acid Nomenclature Quiz and Flashcards

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Questions and Answers

What is the primary function of insulin in relation to adipose tissue?

To activate hormone-sensitive lipase

To regulate the synthesis of triacylglycerol

To inhibit the mobilization of stored fat (correct)

To stimulate the mobilization of stored fat

What is the enzyme responsible for activating fatty acids in the cytoplasm?

Hormone-sensitive lipase

Carnitine acyltransferase I

Adenylate cyclase

Fatty acyl-CoA ligase (correct)

What is the net result of the activation of fatty acids in the cytoplasm?

The consumption of 2 molar equivalents of ATP (correct)

The consumption of 1 molar equivalent of ADP

The generation of 2 molar equivalents of ATP

The consumption of 1 molar equivalent of ATP

Where does the oxidation of fatty acids occur?

In the mitochondria Signup and view all the answers

What is the intermediate involved in the transport of fatty acyl-CoA into the mitochondria?

Acyl-carnitine Signup and view all the answers

Which enzyme is involved in the regeneration of the fatty acyl-CoA molecule in the mitochondria?

Carnitine acyltransferase II Signup and view all the answers

What is the net result of the action of hormone-sensitive lipase and other enzymes on triacylglycerols?

Three moles of free fatty acid and one mole of glycerol Signup and view all the answers

What binds to cell-surface receptors, leading to the activation of adenylate cyclase?

Glucagon, epinephrine, or β-corticotropin Signup and view all the answers

What is the role of PKA in the release of metabolic energy?

It phosphorylates and activates hormone-sensitive lipase Signup and view all the answers

What is the result of the increase in cAMP?

Activation of PKA Signup and view all the answers

What is the substrate for monoacylglycerol lipase?

Monoacylglycerols Signup and view all the answers

What is the hormone that stimulates the activation of hormone-sensitive lipase?

Epinephrine Signup and view all the answers

What is the suffix used in common nomenclature for fatty acid names?

-ic Signup and view all the answers

What is the name of the fatty acid derived from the parent hydrocarbon Octadecane with 2 double bonds?

Octadecadienoic Acid Signup and view all the answers

What is the primary source of fatty acids for oxidation?

Dietary sources Signup and view all the answers

Where are fatty acids stored in the body?

Adipocytes of adipose tissue Signup and view all the answers

What is the result of beta oxidation of fatty acids?

Generation of Acetyl-CoA Signup and view all the answers

Where does beta oxidation of fatty acids take place?

Mitochondria and peroxisomes Signup and view all the answers

What is the end product of β-oxidation of fatty acids with an odd number of carbon atoms?

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

What is the function of methylmalonyl CoA racemase in the β-oxidation of fatty acids with odd number of carbons?

Converting D-isomer to L-isomer Signup and view all the answers

What is the purpose of enoyl CoA isomerase in β-oxidation?

To convert cis double bonds to trans double bonds Signup and view all the answers

What is the final step in the metabolism of propionyl-CoA in the β-oxidation of fatty acids with odd number of carbons?

Conversion to succinyl-CoA Signup and view all the answers

What is the role of biotin-dependent propionyl CoA carboxylase in the β-oxidation of fatty acids with odd number of carbons?

To carboxylate propionyl-CoA Signup and view all the answers

Why do fatty acids with an odd number of carbon atoms require additional enzymes for β-oxidation?

Because they produce acetyl-CoA units and 1 mole of propionyl-CoA Signup and view all the answers

What type of drugs can inhibit carnitine acyltransferases?

Sulfonylurea Signup and view all the answers

What is the most common form of acyl-CoA dehydrogenase deficiency?

Medium Chain Acyl CoA Dehydrogenase Deficiency Signup and view all the answers

What is the diagnostic indicator of Medium Chain Acyl CoA Dehydrogenase Deficiency?

Excessive urinary excretion of medium-chain dicarboxylic acids Signup and view all the answers

What is the primary symptom of Medium Chain Acyl CoA Dehydrogenase Deficiency in the first years of life?

Vomiting Signup and view all the answers

What is the rare inherited disorder characterized by the accumulation of phytanic acid in tissues and serum?

Refsum's disease Signup and view all the answers

What is the recommended dietary restriction to ameliorate the symptoms of Refsum's disease?

Restriction of dairy products and ruminant meat Signup and view all the answers

Study Notes

Clinical Significance of Fatty Acid Deficiencies

Inherited diseases that impair β-oxidation result from deficiencies in acyl-CoA dehydrogenases.
Medium Chain Acyl CoA Dehydrogenase Deficiency is the most common form of acyl-CoA dehydrogenase deficiency.
Symptoms of this deficiency include vomiting, lethargy, and frequently coma, and can be diagnosed by excessive urinary excretion of medium-chain dicarboxylic acids and their glycine and carnitine esters.
Avoiding prolonged fasting is sufficient to prevent clinical problems in this deficiency.

Refsum's Disease

Refsum's disease is a rare inherited disorder in which patients lack the mitochondrial α-oxidizing enzyme.
Patients accumulate large quantities of phytanic acid in their tissues and serum, leading to severe symptoms such as cerebellar ataxia, retinitis pigmentosa, nerve deafness, and peripheral neuropathy.
Restricting dairy products and ruminant meat from the diet can ameliorate the symptoms of this disease.

Hormones and Release of Metabolic Energy

Glucagon, epinephrine, or β-corticotropin stimulate the activation of hormonesensitive lipase.
Hormones bind cell-surface receptors that are coupled to the activation of adenylate cyclase upon ligand binding.
The resultant increase in cAMP leads to activation of PKA, which in turn phosphorylates and activates hormonesensitive lipase.

Generation of Fatty Acids from Triacylglycerols for β-Oxidation

Hormone-sensitive lipase hydrolyzes fatty acids from triacylglycerols.
The resulting diacylglycerols are substrates for either hormonesensitive lipase or for the non-inducible enzyme diacylglycerol lipase.
Finally, the monoacylglycerols are substrates for monoacylglycerol lipase.
The net result of the action of these enzymes is three moles of free fatty acid and one mole of glycerol.

Inhibition of Mobilization of Fatty Acids

Insulin inhibits the mobilization of fat from adipose tissue.
This inhibition is exerted upon adenylate cyclase, preventing the inappropriate mobilization of stored fat when an individual is in a well-fed state.

Activation of Fatty Acids in the Cytoplasm

Fatty acids are activated in the cytoplasm before oxidation in the mitochondria.
Activation is catalyzed by fatty acyl-CoA ligase (also called acyl-CoA synthetase or thiokinase).
The net result of this activation process is the consumption of 2 molar equivalents of ATP.

Fatty Acid Transport to Mitochondria

The transport of fatty acyl-CoA into the mitochondria is via an acyl-carnitine intermediate, generated by the action of carnitine acyltransferase I.
The acyl-carnitine molecule is then transported into the mitochondria where carnitine acyltransferase II catalyzes the regeneration of the fatty acyl-CoA molecule.

Fatty Acid Oxidation (β-Oxidation of Fatty Acids)

Beta oxidation is the process by which fatty acid molecules are broken down in the mitochondria and/or peroxisomes to generate acetyl-CoA for the Krebs cycle.

Mobilization of Fatty Acids for β-Oxidation

The primary sources of fatty acids for oxidation are dietary and mobilization from cellular stores.
Fatty acids from the diet can be delivered from the gut to cells via transport in the blood.
Fatty acids are stored in the form of triacylglycerols primarily within adipocytes of adipose tissue.

β-Oxidation of Lipids with Odd Number of Carbons

Fatty acids with an odd number of carbon atoms yield acetyl-CoA units + 1 mole of propionyl-CoA upon complete β-oxidation.
The propionyl-CoA is converted, in an ATP-dependent pathway, to succinyl-CoA, which then enters the TCA cycle for further oxidation.

β-Oxidation of Lipids with Odd Number of Carbons (Additional Enzymes)

Carboxylation by the biotin-dependent propionyl CoA carboxylase in an ATP-requiring reaction is the first step.
The D- isomer is converted to the L- isomer by methylmalonyl CoA racemase in the intermediate step.
In the final step, the L- isomer is converted to succinyl CoA by methylmalonyl CoA mutase.

Cis Double Bond Conversion

The action of enoyl CoA isomerase is required to handle double bonds at odd-numbered carbons because β-oxidation generates or requires pre-existing double bonds at even-numbered carbons.

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Description

Test your knowledge on how to name fatty acids based on their parent hydrocarbons. Learn the rules and exceptions to confidently identify different types of fatty acids. From butanoic acid to octadecadienoic acid, challenge yourself to master fatty acid nomenclature!

Y1S2 005 II Biochem Fatty Acid Nomenclature

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