Question

1(a) The complete metabolic oxidation of glucose to CO2 and O2 yields 38 ATPs. What is the yield of ATP
from Glc if it is first added to a glycogen polymer before being converted to CO2 and O2? What is the
FRACTIONAL energetic cost in terms of ATP (eg., 1%, 2%, 10%, etc.) of storing glucose as glycogen and
later metabolizing the glycogen rather than directly metabolizing the glucose? Be sure to show your work
and state any assumptions being made. Briefly explain whether this is a big loss of energy due to storage of
glycogen. (Recall that the breakdown of glycogen yields more than one product.)
(b) Glycogen metabolism is heavily regulated, and phosphorylase kinase plays an important role in this
regulation. An individual has a defective liver phosphorylase kinase. Describe what effect this defect will
have on glycogen metabolism in the liver. Describe what effect this defect will have on the ability of this
individual to buffer blood glucose under HIGH and LOW blood glucose conditions.

Answer 1

During glycogensis 2 molecules of ATP used to incorporate one molecule of glucose in glycogen. While during glycogenolysis , there is production of glucose 6 phosphate which enter in to glycolysis. Thus omit requirement of one ATP molecule required in glucose activation.

Total energy produced by glucose , released from glycogen after storage = energy spent in storage -  glucose 6 phosphate energy production in glycolysis

= 39-2

= 37

Total 37 molecule of ATP will be produced. From this glucose released from glycogen.

All the calculations has been shown in digramatic way for easy understanding

B)glycogen phosphorylase is regulatory enzyme of glycogenolytic pathway. Help in degradation of glycogen and releasing of glucose when required like to maintain blood glucose or during exercise in muscle. So in defect in PhK , glucose is not released even in decrese blood glucose level , lead to hypoglycemia which in long run lead to ketone body formation ( ketosis) . In muscle, during exercise, glucose will not release lead to cramps , exercise intolerance , progressive muscle weakness.

Phosphorylase kinase ( PhK) deficiency cause glycogen storage duseas type IX. Phosphorylase kinase is involved in activation of phosphorylase enzyme meiated by hormones. Two firms of PhK deficiency is found -

1) liver PhK deficiency- early childhood hepatomegaly, hypoglycemia, ketosis and growth restriction.

2) muscle PhK deficiency- kind of rare. Exercose in tolerance, myalgia , muscle cramps ,myoglobinuria, progressive muscle weakness.

Even though blood glucose is low ---' stimulation of release of glucagon--- but to decetive PhK , -----, glycogen phosphorylase in not activated------ no release of glucose----- hypoglycemia