WBR270
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 3-year-old boy is brought to the physician’s office with a 3-day history of fever, cough, and runny nose. The mother states that the child is not growing like his siblings before him. Physical examination is remarkable for generalized hypotonia, restricted joint movements, and coarse facial features. Radiographic findings include bullet-shaped phalanges, wedging of the vertebrae, and widening and thickening of the ribs. Which of the following statements is true regarding the impaired cellular organelle involved in this patient's condition?]] |
| Answer A | AnswerA::It is involved in the addition of O-oligosaccharides to serine and threonine residues |
| Answer A Explanation | AnswerAExp::The cellular organelle involved in I-cell disease disease is the Golgi apparatus, which normally modifies N-oligosaccharides on asparagine and adds O-oligosaccharides to serine and threonine residues. |
| Answer B | AnswerB::Modification of N-oligosaccharides on glycine |
| Answer B Explanation | AnswerBExp::Modification of N-oligosaccharides is on asparagine. |
| Answer C | AnswerC::It is involved in the addition of glucose -6-phosphate to proteins |
| Answer C Explanation | AnswerCExp::The Golgi apparatus is involved in the addition of mannose-6-phosphate to specific lysosomal proteins. |
| Answer D | AnswerD::It is a distribution center of proteins and lipids from the endoplasmic reticulum to the mitochondria |
| Answer D Explanation | AnswerDExp::The Golgi apparatus is a distribution center of proteins and lipids from the endoplasmic reticulum to the plasma membrane, lysosomes, and secretory vesicles. |
| Answer E | AnswerE::It is involved in proteoglycan assembly from prelysosomes |
| Answer E Explanation | AnswerEExp::The Golgi apparatus is involved in proteoglycan assembly from core proteins. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Inclusion cell disease (I-cell disease) is an inherited lysosomal storage disorder characterized by failure of addition of mannose -6- phosphate to lysosome proteins. It usually manifests with coarse facial features, clouded corneas, restricted joint movement, and in the majority of cases, it is fatal in childhood. The disease is caused by defective phosphotransferase enzyme that is located on the Golgi apparatus (involved cellular organelle). The Golgi apparatus is a distribution center of proteins and lipids from the endoplasmic reticulum (ER) to the plasma membrane, lysosomes, and secretory vesicles. It modifies N-oligosaccharides on asparagine and adds O-oligosaccharides to serine and threonine residues. Educational Objective: The cellular organelle involved in I-cell disease disease is the Golgi apparatus. It is a distribution center of proteins and lipids from the endoplasmic reticulum (ER) to the plasma membrane, lysosomes, and secretory vesicles. It modifies N-oligosaccharides on asparagine and adds O-oligosaccharides to serine and threonine residues. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::I-cell disease, WBRKeyword::Golgi apparatus, WBRKeyword::Organelle, WBRKeyword::O-oligosaccharides, WBRKeyword::Serine, WBRKeyword::Threonine |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |