Biochemistry USMLE Step 1 Exam || With Questions & Solutions (Graded A+)

Biochemistry USMLE Step 1 Exam || With Questions & Solutions (Graded A+) Biochemistry USMLE Step 1 Exam || With Questions & Solutions (Graded A+) Allopurinol is used for the treatment of chronic gout because it __________. - ANSWER - Decreases uric acid levels by blocking xanthine oxidase with converts hypoxanthing to xanthine and then to uric acid Lesch-Nyhan is a X-lined recessive disorder due to __________. - ANSWER - absence of HGPRT--thus patients are unable to salvage purines leading to excessive de novov synthesis which then leads to excess uric acid production. The presentation of retardation, cerebral palsy, slef-mutiliation, gout and "crystals in diaper" and self-muilation is most consistent with ________. - ANSWER - Lesch-Nyahan Syndrome What is the treatment for Lesch-Nyhan syndrome? - ANSWER - Allopurinol (inhibits xanthine oxidase in the purine salvage pathway, thus reducing excess production of uric acid) What disorder is associated with hyperuricenmis either due to overproduction or underexcretion of uric acis and is characterized by sodium urate crystal deposits in the joints and soft tissues? - ANSWER - Gout What are some causes of uric acid overproduction in acquired gout? - ANSWER - Leukemia, alcoholism, myelopproliferative syndrome, multiple myeloma, hemolysis, neoplasia, psoriasis What drugs are associated with urate underexcretion in acquired gout? - ANSWER - Aspirin, diuretics, alcohol What is podagra? - ANSWER - Gout of the great toe Monoarticular arthirits of distal joints often with a history of hyperuricemia percipiatated by a sudden change in urate levels (due to large meals, alcohol) is characteristic of ______ and can eventually lead to the formation of _______. - ANSWER - gout; nodular tophi (urate crystals surrounded by fibrous connective tissue) located around the joints and Achilles tendon. How is gout diagnosed? - ANSWER - Detection of negatively bifringent crystals from articular tap, arthritis and hyperuricemia What is the treatment for Gout? - ANSWER - For chronic-allopurinol to lower uric acid levels but NOT for acute treatment. For aute treatment decrease pain and inflammation with colchicines and NSAIDS and avoidance of large meals and ETOH What is colchicine used for and how does it work? - ANSWER - Acute Gout. It prevents neutrophil and leukocyte migration into the joint by binding tubulin, depolarizing microtubules and interfering with motility and degranulation. Note: Indomethacin is more commonly used due to less side effects Achondroplasia involves what defect? - ANSWER - Cell-signaling defect of fibroblast growth factor (FGF) receptor 3 Marfan's syndrome involves a mutation in what? - ANSWER - Fibrillin gene Nucleoside + phosphate= ? - ANSWER - Nucleotide Adenine and Guanine are in what type of nucleic acid?