Integration of Metabolism Flashcards
what is the fed state metabolism controlled by?
- insulin
- pancreas sends insulin to liver, brain, and adipose tissue
how is glucose transferred between blood and tissue
- facilitated diffusion
where does glucose go first after it enters bloodstream and how (2)
- liver
- via portal vein
glycolysis
glucose -> pyruvate -> acetyl-CoA
what tissues pick up glucose (4)
- liver, brain, adipose tissue, muscle
how happens to extra glucose (2)
- stored in muscle and liver as glycogen
- converted to acetyl-CoA in liver for FA synthesis
where do proteins go first from the bloodstream and how? (2)
- liver
- via portal vein
what are amino acids used for in liver and other tissues
- protein synthesis
what happens to extra amino acids in liver?
- broken down to alpha-ketoacids and NH3
what happens to NH3 in the liver
- converted to urea in urea cycle
what happens to carbon skeletons (alpha-ketoacids) in the liver
- eventually converted to acetyl-CoA and used in FA synthesis
what happens to some AA if carbs are low
- some AA used for gluconeogenesis
gluconeogenesis
pyruvate -> glucose
what is the first step in digesting lipids
- emulsify them using bile to form micelles
what happens to emulsified lipids (TAG)
- broken down by intestinal lipases into MAG and 2FA to be absorbed by intestinal cells
chylomicron (3)
- lipoprotein particles made up of TAG, apolipoproteins, and some cholesterol esters
- transports dietary TAG to adipose tissue
- remnants containing cholesterol are delivered to liver
what happens to MAG and 2 FA in the intestinal cells?
- reassembly into TAG and then into chylomicrons
fate of chylomicrons (2)
- released from intestinal cells to lymphatic system
2. eventually merge into bloodstream and is distributed among tissues to be used for energy or stored
lipoprotein lipase function
- breaks down TAG into MAG and 2 FA in tissues
very low density lipoprotein (VLDL)
- transport of endogenous TAGs to adipose tissue via circulation
how is cholesterol synthesized and where
- liver synthesizes cholesterol from acetyl-CoA
low density lipoprotein (LDL) (3)
- used to deliver cholesterol to tissue
- picked up by tissue via receptor mediated endocytosis
- high LDL = atherosclerosis
high density lipoprotein (HDL) (3)
- carried extra cholesterol from tissues back to liver
- known as good cholesterol: high HDL = lower risk of atherosclerosis
- pick up by liver via endocytosis
what is the fasting state metabolism controlled by (2)
- glucagon
- pancreas releases glucagon to the liver
what is the order of molecules used during fasting state?
- free glucose, glycogen, FAs stored in adipose tissue
how is glycogen used during fasting state
- converted to free glucose in bloodstream
what does hormone sensitive lipase released by glucagon do
- break down TAG completely into glycerol and 3 fatty acids
what happens to free FAs during fasting state
- complexed with albumin and delivered to tissues (excluding brain)
how is glucose synthesized during fasting state
- gluconeogenesis in liver from glucogenic AAs and propionyl-CoA
what happens during prolonged fasting (2)
- acetyle-CoA cannot enter TCA cycle because OAA is being used for gluconeogenesis
- acetyl-CoA converted to ketone bodies and released to bloodstream to be used for energy by brain and heart
