When glucose is transported into liver cells, it is modified. A. Name the type of modification...

When glucose is transported into liver cells, it is modified.

A. Name the type of modification to glucose. ________________________________________________________________________

B. In which part of liver cell does this modification occur? ________________________________________________________________________

C. Name the enzyme in liver cells responsible for this modification. ________________________________________________________________________

D. Name the enzyme in brain and muscle cells with the same activity. ________________________________________________________________________

E. What is the significance of this type of modification? ______________________________________________________

Expert Solution

A. When glucose is transported into liver it is modified ( phosphorylated into glucose 6 phosphate ). It is phoshorylated so that it does not come out from the hepatocyte along with the concentration gradient. The negative charge of the phosphate group at 6th position of glucose does not allow the glucose to come out of the cell. Also Glucose 6 phosphate serves as a precursor for glycolytic intermediates. Now the glucose will be oxidised to pyruvate via glycolysis.

B. This modification occurs in the cytosol of liver cell As the all the glycolytic enzymes (glucokinase, isomerase, etc.) Are present in the cytosol of liver cell .

C. Glucokinase is responsible for the phosohorylation of glucose in the liver. It attatches phosphate group at 6th position of glucose converting it into glucose 6 phosphate.

D. Hexokinase is the enzyme present in brain and muscle for the same activity.

E. Significance of this modification:

1.A soon as glucose enters the liver cell it is phosphorylated because the negative charge of the phosphate prevents the glucose from lekaing out of the cell.

2. The glucose 6 phosphate is an important precursor of the intermediates of glycolysis. To give ATP ( which is the energy currency of the cell) glucose needs to be oxidised into pyruvate , and it is not possible without the first step of glycolysis( which is phosphorylation).

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gladiator answered 2 years ago

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