Biochemistry : Lipid Catabolism Enzymes

Study concepts, example questions & explanations for Biochemistry

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Example Questions

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Example Question #1 : Lipid Catabolism Enzymes

What cofactor is required for the oxidation of beta-hydroxyacyl-CoA to beta-Ketoacyl-CoA by hydroxyacyl-CoA dehydrogenase?

Possible Answers:

CoASH

FADH2

FAD

NAD+

NADH

Correct answer:

NAD+

Explanation:

NAD is required  for the oxidation of beta-hydroxyacyl-CoA to beta-Ketoacyl-CoA by hydroxyacyl-CoA dehydrogenase.

L hydroxyacyl coa dh rxn beta ox

Example Question #23 : Catabolic Pathways And Metabolism

What enzyme performs the shown step in beta oxidation?

Acyl coa dh reaction beta ox

Possible Answers:

Thiolase

Acetyl-CoA dehydrogenase

Acyl-CoA oxidase

Acyl-CoA dehydrogenase

CoA dehydroxlase

Correct answer:

Acyl-CoA dehydrogenase

Explanation:

This first step of beta oxidation is catalyzed by acyl-CoA dehydrogenase. One way to remember is that the enzyme is named for exactly what it does: remove a hydrogen (dehydrogenate) from acyl-CoA, which is the reactant. In order to be acetyl-CoA the R-group must specifically be a methyl group.

Example Question #2 : Lipid Catabolism Enzymes

What enzyme performs the shown step in beta oxidation?

Enoyl coa hydratase rxn beta ox

Possible Answers:

Acyl-CoA oxidase

Acyl-CoA hydratase

Enoyl-CoA hydratase

Thiolase

Acyl-CoA dehydrogenase

Correct answer:

Enoyl-CoA hydratase

Explanation:

This second step of beta oxidation is catalyzed by enoyl-CoA hydratase. One way to remember is that the enzyme is named for exactly what it does: adding water (hydrate) across the double bond of enoyl-CoA, which is the reactant. 

Example Question #28 : Catabolic Pathways And Metabolism

What enzyme catalyses the shown step in beta oxidation?

L hydroxyacyl coa dh rxn beta ox

Possible Answers:

Acyl-CoA dehydroxylase

L-hydroxacyl-CoA dehydrogenase

L-hydroxacyl-CoA dehydrogenase

Enoyl-CoA hydratase

Acyl-CoA dehydrogenase

Correct answer:

L-hydroxacyl-CoA dehydrogenase

Explanation:

This third step in beta oxidation is catalyzed by L-hydroxacyl-CoA dehydrogenase. One way to remember is that the enzyme is named for exactly what it does: remove a hydrogen (dehydrogenate) L-hydroxyacyl-CoA (the reactant).

Example Question #29 : Catabolic Pathways And Metabolism

What enzyme catalyses the below step in beta oxidation?

Thiolase rxn beta oxidation

Possible Answers:

Acetyl-CoA synthase

Enoyl-CoA hydratase

Acyl-CoA dehydrogenase

Thiolase

L-hydroxacyl-CoA dehydrogenase

Correct answer:

Thiolase

Explanation:

This fourth step in beta oxidation is catalyzed by thiolase. The reduced form of coenzyme-A is used as a cofactor to cleave the bond between the alpha and the beta carbon.  

Example Question #30 : Catabolic Pathways And Metabolism

Which cofactor is required in the conversion of fatty acyl-CoA to trans enoyl-CoA by acyl-CoA dehydrogenase?

Possible Answers:

Biotin

Pyridoxal 

Water

Correct answer:

Explanation:

 removes two hydrogens to form . These two electrons will be donated to the electron transport chain.

Acyl coa dh reaction beta ox

Example Question #1 : Lipid Catabolism Enzymes

What reaction in beta oxidation does enoyl-CoA hydratase catalyze?

Possible Answers:

The formation of a carbon-carbon double bond by adding water

The addition of water across the carbon-oxygen double bond

The removal of water across the carbon-carbon double bond

The removal of water across the carbon-oxygen double bond

The addition of water across the carbon-carbon double bond

Correct answer:

The addition of water across the carbon-carbon double bond

Explanation:

Enoyl-CoA hydratase catalyzes the the addition of water across the carbon-carbon double bond. 

Enoyl coa hydratase rxn beta ox

Example Question #3 : Lipid Catabolism Enzymes

Which reaction in beta oxidation does hydroxyacyl-CoA dehydrogenase catalyze?

Possible Answers:

Oxidation the gamma carbon

Oxidation of the beta hydroxyl group

Reduction of the beta hydroxyl group

Dehydration of the beta carbon

Dehydration of the carbonyl carbon

Correct answer:

Oxidation of the beta hydroxyl group

Explanation:

Hydroxyacyl-CoA dehydrogenase oxidizes the beta hydroxyl group, forming a carbonyl.

L hydroxyacyl coa dh rxn beta ox

Example Question #4 : Lipid Catabolism Enzymes

What reaction in beta oxidation does thiolase catalyze?

Possible Answers:

Cleavage of the beta carbonyl

Cleavage of the sulfur-carbon bond

Cleavage of the alpha-ketoacyl-CoA

Cleavage of the sulfur-CoA bond

Cleavage of the beta-ketoacyl-CoA

Correct answer:

Cleavage of the beta-ketoacyl-CoA

Explanation:

Thiolase catalyzes the cleavage of the beta-ketoacyl-CoA.

Thiolase rxn beta oxidation

Example Question #6 : Lipid Catabolism

What are the two major products of the thiolase-catalyzed reaction?

Possible Answers:

Acyl-CoA and a fatty acyl-CoA shortened by two carbons

Acyl-CoA and a fatty acyl-CoA shortened by one carbon

Acetyl-CoA and a fatty acyl-CoA shortened by one carbon

Thiol and a fatty acyl-CoA shortened by two carbons

Acetyl-CoA and a fatty acyl-CoA shortened by two carbons

Correct answer:

Acetyl-CoA and a fatty acyl-CoA shortened by two carbons

Explanation:

The two major products of the thiolase-catalyzed reaction are acetyl-CoA and a fatty acyl-CoA shortened by two carbons.

Thiolase rxn beta oxidation

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