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A sample of glycogen from a newborn with liver disease is incubated with inorganic phosphate, normal glycogen phosphorylase, and debranching enzyme. The ratio of glucose-1-phosphate (G-1-P) to glucose formed in the reaction is abnormally high. The patient is most likely deficient in which of the following?
A. alpha-1,6-glucosidase
B.(alpha -1,4 ”alpha-1 ,4) glucan transferase
C.(alpha-1,4 ”alpha-1,6) glucan transferase
D. Glycogen phosphorylase
E. Glycogen phosphorylase kinase
Please answer with ur explanation.
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No one knows the answer or is everyone lazy!!!! I found this question posted by faster,he did post the answer for this but i think its wrong.
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drtense
the answer is c
why do u think the answer is wrong?
give explanation about ur guess .
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the answer c i correct. the reason is that
1. if you look at the stem ,the process of glycogenolysis is described.all the enzymes are provided and the glysogen sample s taken from the patient.it means there is a problem in glycogen structure not with the enzymes of glycogenolysis.
2. if you know how the glycogenolysis enzyme work.the glycogen phosphorylase can only break the alpha1,4 glysosidic bond. and when it nears the branch point it stops and then the debranching enzyme(alpha 1,4:alpha1,4 transferase and alpha1,6 glucosidase) comes in and breaks the alpha 1,4 bond and reattaches the short unit(oligiglucose unit) to the end of another chain. and this same debranching enzyme breaks the alpha 1,6 glycosidic bond and releases gree glucose.this is the only free glucose that is released during this process.
3. now coming back to the question,it says that ratio of glucose-1-phosphate to free glucose is abnormally high.and if they have added all the enzymes then it must because of the glycogen that there is less free glucose. the only 2 diseases that i know have abnormal glycogen structure in liver is Cori's and anderson's.in cori's here is deficiency of debranching enzyme.since the debranching enzyme is added in the sample so it could only be Anderson's disease which is a deficiency of branching enzyme(choice c).there is fewer branches in glycogen so the debranching enzyme doesn't have that many branches to work on so you less free glucose and the ratio b/w G-1-P and free glucose is high.
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thank u neemhakeem
ur explanation is more than enough
i think u should teach biochemistry in usa
god bless u
