Question

Palmitate uniformly labeled with tritium (3H) to a specific activity of 2.48 3 108 counts per minute (cpm) per micromole of palmitate is added to a mitochondrial preparation that oxidizes it to acetyl-CoA. The acetyl-CoA is isolated and hydrolyzed to acetate. The specific activity of the isolated acetate is 1.00 3 107 cpm/$mol. Is this result consistent with the !-oxidation pathway? Explain. What is the final fate of the removed tritium?

Answer 1

Palmitate uniformly labeled with tritium (³H) to a specific activity of 2.48×10⁸ counts per minute (cpm) per micromole of palmitate is added to a mitochondrial preparation that oxidizes it to acetyl-CoA. The acetyl-CoA is isolated and hydrolyzed to acetate. The specific activity of the isolated acetate is 1.00 × 10⁷ cpm/μmol. Is this result consistent with the β-oxidation pathway? Explain. What is the final fate of the removed tritium?

Answer:

Explanation:

Lets look at what the  β-oxidation pathway is all about, The   β-oxidation pathway are associates two dehydrogenase enzymes  with itself. These enzymes helps in the removal of hydrogen-hydrogen bond from a fatty acyl-CoA chain. This process occurs at a -CH₂ - CH₂ - and also at -CH₂-CH(OH)- pathway. However , the overall equilibrium outcome of the reaction simultaneous reaction that takes place involves the loss of one of the two hydrogen when the enoyl-CoA intermediate is  formed. What happens afterwards to the  two other hydrogen in the methyl group of acetyl-CoA is that they come with water.

Now;what is  Palmitate ?

Palmitate is a saturated fatty acid organic compound that comprises of 16 carbons and 31 hydrogen; this typical implies that two unit of  carbon attaches itself to about 4/31 of the total present hydrogen.

In addition to the above mentioned, the expected counts per minute for acetyl-CoA with two acetyl hydrogen out of the four acetyl hydrogen labeled is :

$\frac{2}{4} * 2.8*10^8 \ cpm/ \mu mol* \frac{4}{31} \approx 1.6*10^7 \ cpm/ \mu \ mol$

Then result is obviously higher than the given. Furthermore, Exchange between  β-ketoacyl-CoA and solvent (water) can be loss of tritium ³H.

The final fate of the removed tritium from Palmitate stem from it how it is seen in water as reduced carriers (FADH₂ ,  NADH) which are therefore re-oxidized by the mitochondria.