Question

End product of beta-oxidation of a 16 carbon fatty acid will be

• A. Acyl CoA
• B. Acetyl CoA
• C. Malonyl CoA
• D. Palmitate

Hint:

For any saturated, even-chain fatty acid with $N$ carbon atoms, the number of Acetyl-CoA molecules produced is $N/2$, and the number of beta-oxidation cycles is $(N/2) - 1$.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Beta-oxidation is the primary catabolic pathway for fatty acids, occurring inside the mitochondrial matrix of eukaryotic cells.
During this process, fatty acids are broken down by sequential removal of two-carbon units from the carboxyl end of the fatty acyl-CoA chain.

Step 2: Detailed Explanation:
Let us consider a saturated fatty acid with 16 carbons, which is palmitic acid.
First, the fatty acid is activated in the cytosol to form palmitoyl-CoA.
This molecule is transported into the mitochondrial matrix via the carnitine shuttle.
Once inside the matrix, the palmitoyl-CoA undergoes repetitive cycles of beta-oxidation.
Each cycle consists of four enzymatic reactions: oxidation (generating $\text{FADH}_2$), hydration, oxidation (generating NADH), and thiolytic cleavage.
Each complete cycle shortens the fatty acyl chain by two carbons and releases one molecule of Acetyl-CoA.
For a 16-carbon chain, the pathway requires 7 cycles of beta-oxidation.
The final (7th) cycle cleaves a 4-carbon intermediate (acetoacetyl-CoA) into two final molecules of Acetyl-CoA.
Thus, the total metabolic yield from the complete beta-oxidation of palmitic acid is:
\[ \frac{16}{2} = 8 \text{ molecules of Acetyl-CoA} \]
These Acetyl-CoA molecules can subsequently enter the citric acid cycle (TCA cycle) to generate NADH, $\text{FADH}_2$, and GTP/ATP.

Step 3: Final Answer:
The primary organic end product of the beta-oxidation of a 16-carbon fatty acid is Acetyl CoA.