WBR0979
Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
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Exam Type | ExamType::USMLE Step 1 |
Main Category | MainCategory::Biochemistry |
Sub Category | SubCategory::General Principles |
Prompt | [[Prompt::Shown below is a diagram depicting the sorbitol metabolism. Which of the following correspond to the cofactors X and Y respectively? |
Answer A | AnswerA::NADPH and NAD+ |
Answer A Explanation | AnswerAExp::NADPH and NAD+ are the correct cofactors corresponding to X and Y respectively. |
Answer B | AnswerB::NAD+ and NADPH |
Answer B Explanation | AnswerBExp::This answer is incorrect. NADPH and NAD+ are the correct cofactors corresponding to X and Y respectively. |
Answer C | AnswerC::ATP and NAD+ |
Answer C Explanation | AnswerCExp::This answer is incorrect. NADPH and NAD+ are the correct cofactors corresponding to X and Y respectively. |
Answer D | AnswerD::NADPH and ADP |
Answer D Explanation | AnswerDExp::This answer is incorrect. NADPH and NAD+ are the correct cofactors corresponding to X and Y respectively. |
Answer E | AnswerE::NAD+ and ATP |
Answer E Explanation | AnswerEExp::This answer is incorrect. NADPH and NAD+ are the correct cofactors corresponding to X and Y respectively. |
Right Answer | RightAnswer::A |
Explanation | [[Explanation::NADPH is the reduced form of NADP+ and NAD+ is the oxidized form of NADH. These cofactors play a role as electon carriers and donors in redox reactions. Glucose is converted to sorbitol under the action of aldose reductase which requires NADPH as a cofactor. Sorbitol is converted to fructose under the action of orbitol dehydrogenase which requires NAD+. Shown below is a diagram depicting the metabolism of sorbitol.
Educational objective: Glucose is converted to sorbitol under the action of aldose reductase which requires NADPH as a cofactor. Sorbitol is converted to fructose under the action of sorbitol dehydrogenase which requires NAD+. Reference:
First aid for USMLE step 1, 2013. Page 104. |
Approved | Approved::No |
Keyword | WBRKeyword::NADPH, WBRKeyword::NAD+, WBRKeyword::fructose, WBRKeyword::cofactor |
Linked Question | Linked:: |
Order in Linked Questions | LinkedOrder:: |