fed and fasted states Flashcards
how long does the fed/post-prandial state last?
2-3 hours
major storage form of fuel
triacylglycerol
major source of energy for overnight fast
fat
fates of glucose (3)
1- used for energy
2- stored as glycogen
3- converted to fat and stored
where is excess glucose converted to fat?
mainly liver, adipocytes are also able
how is fat exported from the liver?
TAG is exported from the liver as VLDL
what stimulates protein synthesis in mm?
insulin
fates of amino acids (3)
- used for protein synthesis (induced by insulin)
- catabolized for energy
- excess aa are token down- urea excreted and carbon skeletons used to make fat
how does the liver “trap” glucose?
glucose is trapped in the liver by phosphorylation- glucokinase phosphorylates
what increases the activity of glucokinase? (2)
- increased glucose concentration (bc of high km)
- insulin
amount of glucose used by the brain/day in the fed state
150 g/day
which tissues do not use insulin for glucose uptake?
CNS, liver, RBCs
why do RBCs require glucose for energy?
they lack mitochondria, must use glucose for glycolysis
site of amino acid catabolism? exception?
liver is the main site of amino acid catabolism, exception is branched chain aa (isoleucine, leucine and valine) that can be oxidized by muscle
how long after a meal does gluconeogenesis begin?
4 hours
steps in glycogenolysis (7)
- glucagon causes increase in cAMP
- cAMP stimulates PKA
- PKA phosphorylates/activates glycogen phosphorylase
- glycogen phosphorylase breaks down glycogen into glucose-1-phosphate
- g-1-p is converted to g-6-p
- g-6-p is dephosphorylated by glucose-6-dephosphorylase
- glucose is released into the blood
major fuel of the body during fasting
fatty acids
what are the breakdown products of TAG?
glycerol- used in glucoeogenesis
fatty acids- feed into TCA cycle for ATP synthesis
what transports free fatty acids in the blood?
albumin
substrates for gluconeogenesis (3)
amino acids (alanine and glutamine)
lactate- from RBC glycolysis
glycerol - from TAG
sites of gluconeogenesis
liver and kidney
2 aa used most in gluconeogenesis
alanine and glutamine
role of glutamine in kidney gluconeogenesis
buffers ketoacidosis
site of ketone body production
liver
when during a fast does ketone body levels increase? large increase?
18-24 hrs
large increase at 3-5 days
how are ketone bodies made?
partial oxidation of fatty acids in liver
which tissues primarily uses ketone bodies for fuel?
1*= muscle
can also be used by brain
main fuel during starvation
fatty acids and ketone bodies
what happens to glucose use by brain after ketone bodies available?
once ketone bodies available, glucose use by the brain decreases from 150 g/day to 40 g/day
what is “adaptation” during starvation?
when use of ketone bodies increases, demand for glucose decreases thus gluconeogenesis decreases and protein breakdown in decreased, ultimately increases survival
what factor will increase the use of ketones for fuel?
increased length of fast
what can be used as an index for protein catabolism? exception?
urea excretion, exception is GI losses or wounds
preferred fuel of mm in fasted, resting state
fatty acids
type of exercise that increases use of glucose
high intensity
type of exercise that increases use of fatty acids
sustained exercise
what will accumulate with very intense exercise?
lactate
