Biochemistry : Lipid Catabolism Energetics

Study concepts, example questions & explanations for Biochemistry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Lipid Catabolism Energetics

Suppose that a fatty acid containing twelve carbons is broken down via beta oxidation. How many total molecules of ATP will be generated from this fatty acid?

Possible Answers:

Correct answer:

Explanation:

To answer this question, we'll need to keep in mind some of the highlights of beta oxidation. When a fatty acid is broken down by this method, the hydrocarbon chain is broken down two carbons at a time through a series of repeating reactions. These two carbons come off in the form of acetyl-CoA, with an additional generation of one molecule each of NADH and . Since we know the original chain we're starting with contains twelve carbons, we know that there will be six molecules of acetyl-CoA produced. Furthermore, in order to generate these six molecules, beta-oxidation must proceed five times. Thus, we are going to have five molecules of NADH and five molecules of . The acetyl-CoA generated from beta oxidation is able to enter the citric acid cycle. For each molecule of acetyl-CoA that goes through the cycle, 1 molecule of ATP, 1 molecule of , and 3 molecules of NADH are generated. Therefore, since six molecules will be sent into the citric acid cycle, there will be a total generation of six molecules of ATP, six molecules of , and eighteen molecules of NADH. Now, we need to add everything up. So far, we have six molecules of ATP. We also have five molecules of NADH from beta-oxidation, and eighteen from the citric acid cycle, for a total of twenty-three. We've also obtained five molecules of  from beta-oxidation, and another six from the citric acid cycle for a total of eleven. All of the NADH and  that was generated from these reactions can donate their electrons into the electron transport chain to generate ATP. The rule of thumb is that for every NADH,  molecules of ATP are produced. And for every molecules of ,  molecules of ATP is made. So, we have:

And if we add to this the six ATP that was generated directly by substrate-level phosphorylation in the citric acid cycle, that gives us a total of:

Example Question #22 : Lipid Catabolism

Consider the beta-oxidation of palmitate, a sixteen-carbon fatty acid chain. 

If we look only at the formation of acetyl-CoA, how many acetyl-CoA are produced by the the oxidation of palmitate compared to the oxidation of glucose? 

Possible Answers:

 times as many acetyl-CoA are produced by the oxidation of palmitate than glucose

 times as many acetyl-CoA are produced by the oxidation of glucose than palmitate

 times as many acetyl-CoA are produced by the oxidation of palmitate than glucose

They both form an equal number of acetyl-CoA 

Correct answer:

 times as many acetyl-CoA are produced by the oxidation of palmitate than glucose

Explanation:

Palmitate is a sixteen-carbon chain and its beta-oxidation will produce 8 acetyl-CoA molecules, since each acetyl-CoA is two-carbons long. Glucose, on the other hand, will be broken down to form 2 acetyl-CoA molecules. Therefore, palmitate forms 4 times as many acetyl-CoA molecules. 

Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: