Question

Compare and contrast rates of glycogen metabolism in liver and muscle cells based on hormone stimulation and energy charge of the cell.

Part 1 complete the table by replacing question mark (?) with “high” or “low” as required.

Cell	Blood [insulin] (high/low)	Blood [glucagon] (high/low)	Glycolysis rate1 (high/low)	Glycogen breakdown rate (high/low)	Glycogen synthesis rate (high/low)	Glucose release rate2 (high/low)
Liver	High	Low	Low	?	?	?
Liver	High	Low	High	?	?	?
Liver	Low	High	Low	?	?	?
Liver	Low	High	High	?	?	?
Muscle	High	Low	Low	?	?	?
Muscle	High	Low	High	?	?	?
Muscle	Low	High	Low	?	?	?
Muscle	Low	High	High	?	?	?
Muscle	High	Low	Low	?	?	?
1Rate is high or low based on energy charge of the cell and not owing to [glucose] in cell 2Release means transport from the cell to the blood. Low rate could mean no detectable rate

Part 2. (Each row in the table is a separate condition. Interpret each condition independently)

Explain how the conditions regulate specific enzymes to stimulate or inhibit the rates of glycogen breakdown and glycogen synthesis.

Explain glucose release

Answer 1

For better understanding read the statements given under the table first and then observe the table.

Cells	blood [insulin]	blood [glucagon]	Glycolysis rate1	Glycogen breakdown rate	Glycogen synthesis rate	Glucose release rate2
Liver	High	Low	Low	Low	Low	Low
Liver	High	Low	High	High	Low	High
Liver	low	high	low	Low	Low	Low
Liver	Low	high	high	low	high	low
Muscle	high	low	low	high	low	low
Muscle	high	low	high	low	high	low
Muscle	low	high	low	high	low	low
Muscle	low	high	high	low	high	low
Muscle	high	low	low	high	low	low

2)

When Liver glycolysis rate(1) is low,it means it is less active.Thus all processes in liver happens at low rate.So no effect of hormones on Liver.

When Liver glycolysis rate(1) is high it means it is active enough.It's action depends upon concentration of insulin and glucagon.And it act accordingly.

Insulin acts on both Liver and Muscle,whereas Glucagon acts only on Liver.Thus glucose release by muscle irrespective of inulin and glucagon concentration is negligible.So it will be always low.

When muscle cells are active i.e.glycolysis rate(1)is high and have enough Energy,no need of additional glucose,thus breakdown of glycogen will be low,glycogen synthesis will be high.

When muscle cells are less active i.e.glycolysis rate(1)is low(1),it needs glucose so it breaks glycogen.If insulin is high it starts glycogenesis with inflow of glucose molecules into muscle cells.If insulin levels are low it will breaks glycogen but donot involve in glycogen synthesis,because new glucose molecules are not available to muscle cells.