fed and fasted states Flashcards

1
Q

how long does the fed/post-prandial state last?

A

2-3 hours

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2
Q

major storage form of fuel

A

triacylglycerol

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3
Q

major source of energy for overnight fast

A

fat

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4
Q

fates of glucose (3)

A

1- used for energy
2- stored as glycogen
3- converted to fat and stored

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5
Q

where is excess glucose converted to fat?

A

mainly liver, adipocytes are also able

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6
Q

how is fat exported from the liver?

A

TAG is exported from the liver as VLDL

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7
Q

what stimulates protein synthesis in mm?

A

insulin

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8
Q

fates of amino acids (3)

A
  • used for protein synthesis (induced by insulin)
  • catabolized for energy
  • excess aa are token down- urea excreted and carbon skeletons used to make fat
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9
Q

how does the liver “trap” glucose?

A

glucose is trapped in the liver by phosphorylation- glucokinase phosphorylates

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10
Q

what increases the activity of glucokinase? (2)

A
  • increased glucose concentration (bc of high km)

- insulin

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11
Q

amount of glucose used by the brain/day in the fed state

A

150 g/day

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12
Q

which tissues do not use insulin for glucose uptake?

A

CNS, liver, RBCs

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13
Q

why do RBCs require glucose for energy?

A

they lack mitochondria, must use glucose for glycolysis

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14
Q

site of amino acid catabolism? exception?

A

liver is the main site of amino acid catabolism, exception is branched chain aa (isoleucine, leucine and valine) that can be oxidized by muscle

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15
Q

how long after a meal does gluconeogenesis begin?

A

4 hours

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16
Q

steps in glycogenolysis (7)

A
  • 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
17
Q

major fuel of the body during fasting

A

fatty acids

18
Q

what are the breakdown products of TAG?

A

glycerol- used in glucoeogenesis

fatty acids- feed into TCA cycle for ATP synthesis

19
Q

what transports free fatty acids in the blood?

20
Q

substrates for gluconeogenesis (3)

A

amino acids (alanine and glutamine)
lactate- from RBC glycolysis
glycerol - from TAG

21
Q

sites of gluconeogenesis

A

liver and kidney

22
Q

2 aa used most in gluconeogenesis

A

alanine and glutamine

23
Q

role of glutamine in kidney gluconeogenesis

A

buffers ketoacidosis

24
Q

site of ketone body production

25
when during a fast does ketone body levels increase? large increase?
18-24 hrs | large increase at 3-5 days
26
how are ketone bodies made?
partial oxidation of fatty acids in liver
27
which tissues primarily uses ketone bodies for fuel?
1*= muscle | can also be used by brain
28
main fuel during starvation
fatty acids and ketone bodies
29
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
30
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
31
what factor will increase the use of ketones for fuel?
increased length of fast
32
what can be used as an index for protein catabolism? exception?
urea excretion, exception is GI losses or wounds
33
preferred fuel of mm in fasted, resting state
fatty acids
34
type of exercise that increases use of glucose
high intensity
35
type of exercise that increases use of fatty acids
sustained exercise
36
what will accumulate with very intense exercise?
lactate