Integration of Metabolic Pathways Flashcards
What is the preferred fuel for resting muscle?
FA
What is the preferred fuel for active skeletal muscle?
glucose (has no reservoirs)
Why can’t the liver use ketone bodies?
it doesn’t have acetoacetate succinyl CoA transferase
What are the three ketone bodies?
acetone, acetoacetate, and B-hydroxybutyrate
When would urea excretion be the higher?
urea is a by-product of protein breakdown. Proteins in skeletal muscle is broken down only in response to low blood glucose levels when the reserve of glycogen has run out (aka when gluconeogenesis is needed). So around 12 hours of fasting, you will see high urea excretion
What is unique about metabolism in a re-fed state?
When a fasted or starved person is refed, it takes time for the normal “fed state” to be re-established.
Fat is metabolized as in the fed state.
The liver takes up little glucose, so most glucose goes to muscle, where it is converted to lactate. The liver takes up lactate and makes glucose via gluconeogenesis. It takes several hours for “normal” metabolism to become reestablished
What is a possible consequence of feeding someone who has been starving for a long time long amount of carbs?
Since the body cannot perform normal glycolysis yet (because its receptors have been down regulated during starvation), the liver will perform gluconeogenesis with lactate broken down from skeletal muscle (** represent a unique process), so too many carbs could lead to lactic acidosis. The key is to slowly bring them back to normal metabolism
What is the food source of the liver in the starving state? why?
fatty acids. glucose is gone, AAs are being conserved by muscle.
What is the principle export of the liver in the fed state?
TAG (as VLDLs)
What is the principle export of muscle in the fed state?
nothing
What is the principle export of muscle in the fasting state?
AAs and lactate (anaerobic)
What is the principle export of muscle in the starving state?
lactate (anaerobic)
What is the preferred fuel source of adipose in the fed state? fasting state? starved state?
fed- glucose, FA
fasting- none
starved- none
Does the brain ever export anything at any feeding stage?
No
When do RBCs use ketone bodies?
Never, they only use glucose in all three feeding stages
