[Biochemistry] Purine and Pyrimidine Synthesis

[jshyun320]

What is the difference between purine and pyrimidine synthetic pathways?

A. An early reaction is feedback inhibited by nucleotides in purine synthesis but not in pyrimidine synthesis

B. PRPP is the ribose donor for only purine synthesis

C. The purine bases, but not the pyrimidine bases, use aspartate to furnish a ring nitrogen atom

D. All the intermediates in the purine pathway are ribose phosphate derivatives

E. Folic acid coenzymes function only in pyrimidine biosynthesis




Any ideas??? ​

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[BestDoctorEver]

Is this an mcat type question? Where did you get that question from? I guess I am not near ready for that test.

 

[shaboobly]

Is this an mcat type question? Where did you get that question from? I guess I am not near ready for that test.

it's not mcat type

 

[flashlightpen]

it's not mcat type

Thank god. I nearly had a heart attack. 21 days until my MCAT and I literally did not have a clue.

JESUS FTW!

 

[PanRoasted]

i briefly remember discussion of differences in how purines and activated by ATP or something and then that goes on to regulate pyrimidine synthesis in intro to biochem... so my guess is A. but honestly I have no clue. I think google/wikipedia might be a better resource in this case lol

 

[sciencebooks]

Thank god. I nearly had a heart attack. 21 days until my MCAT and I literally did not have a clue.

JESUS FTW!

Hahaha, mine's soon too and I've just come to the point where I know that's beyond the scope and if it was a FSQ, I'd guess, maybe "mark" it (even though it'd be pointless because I just wouldn't know, lol), and move on.

I was like, "Let's see... purines = A & G = two rings and pyrimidines = C & T = one ring" but that knowledge didn't help me, .

 

[bored]

What is the difference between purine and pyrimidine synthetic pathways?

A. An early reaction is feedback inhibited by nucleotides in purine synthesis but not in pyrimidine synthesis

B. PRPP is the ribose donor for only purine synthesis

C. The purine bases, but not the pyrimidine bases, use aspartate to furnish a ring nitrogen atom

D. All the intermediates in the purine pathway are ribose phosphate derivatives

E. Folic acid coenzymes function only in pyrimidine biosynthesis




Any ideas??? ​

I actually took the time to open my biochem notes and do this one.

I found all of A to C are false, vbut couldn't find that bit about folic acid.

I know for sure D is a correct statement. So guess that one and hope it's now E?

 

[whatdidigetinto]

The answer is E. Tetrahydrofolate is used as a methyl group donor in the reaction that converts dUMP to dTMP.

This is a boards question not an MCAT question so don't worry.

 

[bored]

Boards question? What does that mean.

 

[whatdidigetinto]

Boards question? What does that mean.

It's material covered by one of the exams that you have to sit for in order to practice medicine in the united states. Google ''usmle exam''. You start doing these exams in medical school.

 

[bored]

oh my, you have to know biochem with this much deapth??

 

[whatdidigetinto]

oh my, you have to know biochem with this much deapth??

This is the depth required by the boards. You should see the depth required by your teacher teaching you biochemistry in medical school.