USMLE Step 1 First Aid - Biochemistry 2024 Study Guide(100% Verified)

USMLE Step 1 First Aid - Biochemistry 2024 Study Guide(100% Verified) Side = base + (deoxy)ribose [sugar] Tide = base + (deoxy)ribose [sugar] *Which are the purines?* "pure as gold" = Adenosine, Guanosine *Which are the pyrimidines?* "CUT the pyramid" = Cytosine, Uracil, Thymine - answerWhat is a nucleoside? What is a nucleotide? Which are the purines? Which are the pyrimidines? *Disrupt pyrimidine synthesis* *Leflunomide: *inhibits dihydroorate dehydrogenase *Methotrexatem Trimethoprim and Pyrimethamine 5-Fluorouracil*: inhibit dihydrofolate reductase, resulting in decreased dTMP in humans, bacteria and protozoa respectively. *Disrupt purine synthesis* *6-Mercaptopurine* (6-MP): and its prodrug azathioprine inhibit de novo purine synthesis *Mycophenolate and Ribavirin*: inhibit inosine monophosphate dehydrogenase *Disrupt purine and pyrimidine synthesis* *Hydroxyurea*: inhibits nucleotide reductase - answerIn the nucleotide synthesis pathway, describe how purine synthesis differs from pyrimidine synthesis. Fr the following drugs, describe how they interfere with purine or pyrimidine synthesis. Leflunomide Methotrexatem Trimethoprim and Pyrimethamine 5-Fluorouracil 6-Mercaptopurine Mycophenolate and Ribavirin Hydroxyurea *metabolic deficiency:* - absence of adenosine deaminase resulting in increased dATP which is toxic to lymphocytes - one of the major causes of autosomal recessive SCID *symptoms:* - answerAdenosine deaminase deficie