Welcome everybody. My name is Divine. This is episode 581 of the Divine Intervention Podcast.

In today's podcast, we're going to be continuing the series on the Free 121 for Step 1.

This is going to be part 2. We're going to do questions 11 or 20, God willing.

Let's begin. Question 11 says,

A 60-year-old man comes to the office because of weakness, tingling of his hands and feet,

irritability, and forgetfulness for four months.

Physical examination shows pallor, weakness, and spasticity.

Deep tendon reflexes are increased.

Sensation to vibration is absent in the lower extremities.

Lapse studies show megaloblastic anemia, serum antiparidal cell antibodies, and increased

serum concentrations of methyl malonic acid and total homocysteine. The synthesis of which of the following

amino acids is most likely impaired in this patient, right? So again, like you see for many of these

USMLA questions, it's usually smart to try to work out what's going on first before you start

jumping into

the answers right so we can see clearly that this person appears to have b12 deficiency right

and there's many reasons why we can see that number one the person's methyl malonic acid is

increased remember b12 catalyzes two reactions in the body number one is conversion of methyl malonoonyokoe to soxenoccoa. That's how you

kind of make convert ochin fatty acids to, you can ultimately convert them to glucose. That's like a

TCA cycle intermediate that uses the enzyme methyl malonyokwe mutase. Methyl maloneokoe mutase. Methyl maloneyokoe

mutase uses B12 as a co-factor. So if B12 is not working, your methylmalonic acid levels arise.

And then if you want to go from homocysteine to methyonine, there is an enzyme known as

a methyonine synthase that also uses B12 as a cofactor, right?

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