M3c L32-33

Question 1

Compare the pathways, their products, and roles, that operate in the fed state with those that operate in the fasting state

Answer 1

Fed State (soon after a meal)
Storage of glycogen and fat
ATP production
Signaled by insulin
Starved state (>24 hours since a meal)
No glycogen left
Fat hydrolysis and fatty acid oxidation
Liver producing ketone bodies, metabolic state goes up
Small amounts of glucose from fat (from glycerol, odd chain Fatty acids)
Breakdown of muscle protein
Liver producing glucose and ketone bodies
Signaled by glucagon

Question 2

Briefly describe the synthesis and use of ketone bodies

Answer 2

when there is a lot of Acetyl-CoA, the liver will convert that to ketone bodies and send them to the bloodstream to go to
other tissues in other organs
there is a lot of A-CoA in the liver because there is not enough pyruvate to convert oxaloacetate to enter TCA cycle

Question 3

Explain (using examples from carbohydrate metabolism) the roles of phosphorylation and dephosphorylation of enzymes and how this relates to glucose homeostasis

Answer 3

Insulin stimulates a phosphatase that takes off the phospho group from PFK2 (fed state)
Increases [F-2,6-bisP]
PFK1 is more active
Glycolysis is active
Glucagon activates the kinase to attach a phospho group to make PFK2 (starved state)
Decreases [F-2,6 bisP]
PFK1 is less active
Gluconeogenesis is active
Insulin and glucagon stimulate enzymes that determine whether PFK2 is phosphorylated or not and whether PFK2 is active or not, influences level of fructose 2,6 bisphosphate to determine level of glycolysis or gluconeogenesis

Question 4

Explain reciprocal hormonal regulation of glycolysis and gluconeogenesis

Answer 4

a kinase stimulated by glucagon, phosphorylates PFK2, glycolysis is active
a phosphatase dephosphorylates it, stimulated by insulin, gluconeogenesis is active
same with LPK, when LPK is less active, phosphorylated, gluconeogenesis is active
when LPK is more active, dephosphorylated, glycolysis is active

Question 5

Describe the roles of glucagon and insulin on glucose homeostasis

Answer 5

glucagon stimulates glycogen breakdown so the body can have more glucose
insulin stimulates the formation of glycogen to store the glucose and glucose uptake from the blood

Question 6

Briefly explain why type I diabetes causes the production of ketone bodies

Answer 6

there is a loss of glucose homeostasis
Body thinks it’s in a starved state, not enough insulin, liver does gluconeogenesis, puts even more glucose into the bloodstream
glucose not taken up by the liver
liver is gluconeogenic and ketogenic even with high blood glucose
protein and fat are being broken down, meaning there is a high amount of triglycerides and free FA in the body, leading to ketoacidosis