Question

While feverishly studying for this test, you suddenly realized that it had been over 12 hours since you last ate. You then took a break, drove over to Waffle House (restuarant), and ate a huge breakfast. Please describe the following IN ORDER:

a) your blood glucose and hormonal status, both before and after your meal;

b) what metabolic processes were up-regulated before and after your meal;

c) what metabolic processes were down-regulated before and after you meal;

d) what specific enzymes were affected and in what direction in (b) and (c) above;

e) why your answers to (b) and (c) above make sense for you as a complex, multicellular, energy-conscious organism.

Answer 1

A) The blood-glucose level was low before the well fed state. Also leading to a decrease in insulin secretion and a rise in glucagon secretion.

B)Fasting- Upregulation:

Glycogen breakdown is upregulated upon stimulation of glucagon by triggering the cyclic AMP cascade resulting in inhibition of glycogen synthase.

Gluconeogenesis in the liver.

Fatty acid metabolism upregulated reported higher plasma FFA level.

Well fed state -Upregulated:

Glucose and amino acids are transported from the intestine to the blood..

The dietary lipids are packaged into chylomicrons and transported to the blood by the lymphatic system.

Insulin upregulated.

Glycogen synthesis upregulated.

C) Fasting- Downregulation:

Fatty acid synthesis is downregulated upon glucagon stimulation causes inhibition of fatty acid synthesis by inhibiting the production of pyruvate and inhibiting acetyl CoA carboxylase.  

Glycolysis is downregulated by lowering the level of F-2,6-BP.

Fed state downregulated:

Glucogon downregulated.

D) Insulin decreased during fasting.

Glucagon increased during fasting.

Insulin increases in well fed state.

Glucagon and fatty acid metabolism decreased in well fed state.

E) Even after well fed state, glucose is not absorbed immediately by liver, but rather leaves it for the peripheral tissues leaves to remain in a gluconeogenic mode.

Blood glucose level keeps increasing, the liver completes the replenishment of its glycogen stores and begins to process the remaining excess glucose for fatty acid synthesis.