A 4-month-old male is brought to the pediatrician with signs of developmental delay, enlarged liver and spleen, and abnormal respiratory sounds and eye movements. Investigations reveal blood cells with significant accumulations of sphingomyelin. The accumulations are traced to a defect in the gene responsible for enzymatic degradation of sphingomyelin, leading to misfolding of the gene product and its subsequent degradation. Based on the outcomes of the investigations, which of the following best explains the accumulations? Defect in addition of mannose 6-phosphate to sphingomyelinase polypeptides Defect in movement of vesicles containing sphingomyelinase polypeptides from the Golgi along microtubules Sphingomyelin is degraded by lysosomes Sphingomyelinase polypeptides are degraded by proteasomes Sphingomyelinase polypeptides are secreted from cell
Added by Robert S.
Close
Step 1
These findings suggest a lysosomal storage disorder, specifically a sphingolipidosis. Investigations reveal blood cells with significant accumulations of sphingomyelin. This suggests a defect in the degradation of sphingomyelin. The question asks for the best Show more…
Show all steps
Your feedback will help us improve your experience
Jennifer Stoner and 98 other Biology educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
A 3-month-old male was brought into the emergency room suffering from severe fasting hypoglycemia. On physical examination, he was found to have hepatomegaly. Laboratory tests indicated that he also had hyperlacticacidemia (acidosis). A liver biopsy indicated hepatocytes contained greater than normal amounts of glycogen with normal structure. 1. From the list below, which enzyme is defective based on the patient symptoms and clinical findings? For each enzyme, provide a rationale for why it can or cannot be the defective enzyme in this patient. (Each answer must also include reference to liver and glycogen pathology) • Glycogen synthase • Glycogen phosphorylase (liver) • Glucose-6-phosphatase 2. What is hyperlacticacidemia and why is it dangerous? Based on the enzyme defect, provide a biochemical reason for why this patient has hyperlacticacidemia. 3. What would be the recommended dietary treatment for this patient?
Bryan V.
A 3-month-old female seemed normal until she developed seizures. The infant became progressively worse, showing hypotonia (low muscle tone or muscle weakness), psychomotor retardation, and poor head control. She had lactic acidosis and an elevated plasma pyruvate level, both more than seven times the normal amount. Plasma alanine concentration was high, and an alanine load failed to induce a normal gluconeogenic response. Pyruvate carboxylase activity was measured using extracts of cultured skin fibroblasts and was found to be less than 1% of the normal level. Both the mother and the father had intermediate levels of fibroblastic pyruvate carboxylase. Fibroblasts from the patient accumulated five times greater than normal amounts of lipid. A fibroblast is a common cell in connective tissue that secretes collagen. Pyruvate carboxylase catalyzes the following reaction: Pyruvate + CO2 + ATP + H2O -> oxaloacetate + ADP + 2H+. Glutamine greatly stimulated the growth of fibroblasts from a patient with pyruvate carboxylase deficiency. Why?
Dominador T.
Phenylketonuria and Galactosemia In humans there is a disease called Phenylketonuria (PKU) which is caused by a recessive allele. People with this disease have a defective enzyme and cannot break down the amino acid phenylalanine. This disease can result in mental retardation or death. Let “E” represent the normal enzyme, and “e” the defective enxyme. Also in humans is a condition called galactose intolerance or galactosemia, which is also caused by a recessive allele. Let “G” represent the normal allele for galactose digestion and “g” represent the allele for galactose intolerance. In both diseases, normal dominates over recessive. Complete a Punnett square for two adults are heterozygous for both traits What is the probability of having a child without either disease? What are the chances of having a child that has only PKU, not galactosemia? What are the chances of having a child with both diseases?
Shaiju T.
Recommended Textbooks
Biology for AP Courses
Objective Biology for NEET
Introduction to General, Organic and Biochemistry
Transcript
Watch the video solution with this free unlock.
EMAIL
PASSWORD