The following questions concern individuals that have glycogen storage disease t
ID: 206687 • Letter: T
Question
The following questions concern individuals that have glycogen storage disease type VII (Tarui disease). This disease is a rare autosomal recessive disorder that results from a deficiency in the M (muscle isoform) of phosphofructokinase
1. Q1. Explain why this disorder is characterized by abnormal deposition of glycogen in the muscle. In your answer you should detail the steps involved in the biosynthesis of glycogen and indicate the regulation that leads to this phenotype.
Q2. You take a muscle biopsy from an individual and perform an experiment to measure oxygen consumption and ATP production by the muscle. Draw a graph of oxygen concentration vs. time for the following conditions. A) citrate + malate + ADP; B) glucose + malate + ADP, C) succinate + ADP. Indicate how (or if) these curves are different from normal controls.
Explanation / Answer
The storage of glycogen could be seen in muscle, liver, heart, brain and kidney. Glycogen storage disorders are metabolic disorders which happen due to deficiency of a gene/enzyme. The deficient enzyme controls either the glycogen synthesis, its deposition abnormally or the conversion of glycogen to glucose. The reactions and the enzymes involved are in glycogen synthesis..... glucose-----> glucose-6-phospohate----->glucose-1-phosphate-------->Udp-glucose----->glycogen hexokinase, phosphoglucomutase1,Udp pyrophosphorylase, glycogen synthase are the enzymes. The enzymes and reactions involved in glycogenolysis are........... glycogen-------->glucose-1-phosphate--------->glucose-6-phosphate------glucose In glycogenolysis the enzymes involved are glycogen phosphorylase (a&b), phospholgucomutase and glucose-6-phosphatase. Glucose-6-phosphatase deficiency, liver phosphorylase deficiency and deficiency of debranching enzyme glucosidase leads to abnormal accumulation of glycogen in the liver.
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