SDK
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Which of the following tissue is able to convert Glycogen into Glucose????
a)Pancreas
b)Kidney
c)Adipose
d)Muscles
e)RBCs
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| kingsofke
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d
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| SDK
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Muscle donot contain Glucose 6 phosphatase.....It is B..other most imp one is LIVER
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| kingsofke
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I read that only liver has Glucose 6 Phosphatase???
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| SDK
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Ok....this is written in Kaplan bio:.....
Now see the page no: 149 answer no: 173 in Pretest Bio:.......
B/c of that point I post this topic......share ur knowlegde....
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| azygous
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kidney??? definately not Musle..
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| mildus
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kidney also contributes to gluconeogenesis about 20 %
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| SilatK
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Agree Kidney
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| mazinger
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its obviously muscle.. in postabsorptive state.. Kaplan Biochem book 2002, pg 157-8-9.
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| mitali
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the Q asks of one of the ways of getting glucose - by breaking down glycogen. skeletal muscle is the largest consumer of body fuels - glucose & fatty acids. muscle, like liver keeps glucose in the storage form which is glycogen. But, liver, when the need arises for body fuel readily makes available glucose to the rest of the body. skeletal muscles like to keep glucose to themselves for later usage. they keep it in glucose 1 P form which doesn't leak out of cell. now, this 1P form could have converted to glucose 6P and then glucose and left the muscle cell. but the muscle cell lacks G6Phosphatase which can convert it to Glucose 6P. expectedly, this reaction takes in the liver. in summary, i think both muscle & liver store glucose in a branched form - glycogen and when needed, under certain hormone triggers ( epinephrine in the muscle ) unbranches back to glucose forms - the only difference being liver goes the full way & makes glucose & makes it available for the rest of the body. the muscle is selfish and keeps it frozen in the Glucose 1 P state. and i don't think, with due respect, mildus, that we should include gluconeogenesis & kidney role here, as it is a completely different pathway, having nothing to do with glycogen & using other substrates like amino acids, lactate & glycerol 3 phosphate. I don't know how the Q was exactly framed, but i would still go for muscle as the answer if liver is not an option...please clarify....
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| Thunderball65
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the answer is kidney.
free glucose can be formed in the liver and kidney. glycogenolysis in muscle leaves glycogen as glucose 1-p.
my info comes from looking through lippincott biochem. except i can't find info about kidney gluconeogenesis, except for the statement above. does anyone know where i can find some more info. i have looked through kaplan, lippincott and the devlin biochem book.
Edited by Thunderball65 on 11/07/05 - 11:01 AM
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| mildus
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Glycogen is present in almost every cell, but the most important localization is in the liver and muscles.
The liver has an enzyme called Glucose 6 phosphatase which allows to get free glucose from glycogen. This enzyme is also present in enterocytes and epithelial cells of renal tubuls (so that glucose which is absorbed can be transfered to the blood and not kept in these epithelial cells).
Muscles don't have that enzyme and that is why glucose obtained from glycogen in muscles stays in form of glucose 6 phosphate.
So, in muscle we have glycogen conversion to glucoso 6 phosphate which can go to glycolysis. In the liver, glycogen converts to glucose 6 phoshate which is then converted to free glucose by a specific enzyme and then glucose goes into the blood.
So, the answer should be the LIVER, but it isn't offered in the question. So I would say the KIDNEY and it is based on my two assumptions:
1. almost every cell has at least a little of glycogen (so as the cells in kidneys)
2. presence of enzyme called glucose 6 phosphatase in epithelial cells of the renal tubules
If these assumptions are not true or not true enough, then my conclusion isn't correct.
The problem is that we don't know what do they really ask in this question (it is not clear enough). The answer could also be MUSCLE if they don't think of conversion of glycogen to free glucose when they say conversion of glycogen to glucose.
And, Mitali, of course, I agree with you, gluconeogenesis doesn't have anything to do with this question, I have only wanted to stress that information when it was about the kidney.
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| Thunderball65
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oops i meant to say kidney glycogenolysis not kidney gluconeogenesis
mildus i agree with your assumptions. The other point about the questions is that we need to look at the question exactly how it is stated not on how in could be stated, or could be meaning.
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| mildus
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that's right
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| Julia N.G.
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I suppose the answer should be kidney. The conversion of glucose-6-phosphate to glucose, which occurs in the liver, kidney and intestine, by the action of glucose-6-phosphatase does not occur in skeletal muscle as these cells lack this enzyme.
Edited by Julia N.G. on 11/16/05 - 12:36 PM
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| mildus
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