The chapter sections to review are given in parentheses at...

The chapter sections to review are given in parentheses at the end of each question. Arachidic acid $\mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{16}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}$ is a $\mathrm{C}_{20}$ fatty acid found in peanut and fish oils. (18.6,18.7) a. Draw the condensed structural formula for the activated form of arachidic acid. b. Indicate the $\alpha$ - and $\beta$ -carbon atoms in arachidoyl-CoA. c. How many cycles of $\beta$ -oxidation are needed? d. How many acetyl-CoA are produced? e. Calculate the total ATP yield from the complete $\beta$ -oxidation of arachidic acid by completing the following: PICTURE AND TABLE CANT COPY

The chapter sections to review are given in parentheses at the end of each question.
Arachidic acid $\mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{16}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}$ is a
$\mathrm{C}_{20}$ fatty acid found in peanut and fish oils. (18.6,18.7)
a. Draw the condensed structural formula for the activated form of arachidic acid.
b. Indicate the $\alpha$ - and $\beta$ -carbon atoms in arachidoyl-CoA.
c. How many cycles of $\beta$ -oxidation are needed?
d. How many acetyl-CoA are produced?
e. Calculate the total ATP yield from the complete $\beta$ -oxidation
of arachidic acid by completing the following:
PICTURE AND TABLE CANT COPY

Key Concepts

Fatty Acid Activation

Fatty acid activation is the process by which a fatty acid is converted into its acyl-Coenzyme A (acyl-CoA) form by the addition of Coenzyme A. This activation step requires ATP and is essential because it primes the fatty acid for subsequent catabolic processes, such as transport into the mitochondria and ?-oxidation.

?-Oxidation

?-Oxidation is the metabolic pathway in which fatty acids are broken down in a series of cyclic reactions to produce acetyl-CoA. Each cycle of ?-oxidation involves four main reactions—oxidation, hydration, a second oxidation, and thiolysis—resulting in the removal of a two-carbon acetyl-CoA unit from the fatty acid chain. This process is crucial for converting fatty acids into usable energy.

Alpha and Beta Carbons in Fatty Acids

The alpha and beta carbons refer to the positions relative to the carbonyl group in the acyl-CoA molecule. The alpha carbon is the first carbon adjacent to the carbonyl group, while the beta carbon is the second carbon away. These positions are important in enzymatic reactions during ?-oxidation, where specific enzymes recognize and act upon the ?-carbon to facilitate the cleavage of the fatty acid chain.

Acetyl-CoA Production

Acetyl-CoA production is a key outcome of ?-oxidation, with each cycle yielding one acetyl-CoA molecule. Acetyl-CoA serves as a central metabolic intermediate, entering the citric acid cycle where it is oxidized to produce energy in the form of ATP, making it critical for cellular energy metabolism.

ATP Yield Calculation from Fatty Acid Oxidation

The ATP yield calculation from fatty acid oxidation involves summing the energy contributions from the acetyl-CoA molecules produced (which enter the citric acid cycle), as well as the NADH and FADH2 molecules generated during each cycle of ?-oxidation. These cofactors feed electrons into the electron transport chain where oxidative phosphorylation produces additional ATP. This quantitative assessment is essential for evaluating the energy efficiency of fatty acid metabolism.

Transcript

00:01 In this problem, we are asked to draw the condensed structural formula for the activated form of erichitic acid and indicate the alpha and beta carbons in erichidal co -a.

00:10 We are then asked how many cycles of beta oxidation are needed, how many acetylcoa molecules are produced, and then to complete a table describing the total atp yield from complete beta oxidation.

00:22 Starting with part a, we are asked to draw the condensed structural formula for the activated form of erichitic acid.

00:28 In fatty acid activation, we find our fatty acyl co -a through a combination of our starting fatty acid, which is erichitic acid here, and co -enzyme a.

00:40 We'll see that what i've written here in red on co -enzyme a forms a bond with this carbon on our fatty acid to yield the fatty acyl -coa.

00:51 So the fatty acyl -coa product looks like this.

00:56 And you'll notice that the contribution from co -enzyme a is shown here.

01:00 Again in red.

01:02 Now we can determine our alpha and beta carbons.

01:05 We know that our alpha carbon is the carbon atom next to the ketone group, so it is this carbon here.

01:11 And we also know that our beta carbon is next to our alpha carbon, so it will be located here.

01:18 Next we are asked how many cycles of beta oxidation are needed.

01:22 We know that for every cycle of this process, two carbon units are cleaved off.

01:27 We have 20 carbon units total and 18 that we wish to cleave located here.

01:33 So we know that we need nine cycles total if we are cleaving two carbon units per cycle...

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