drk1980
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Can anybody gv a detailed account of processes in the LIVER regarding fuel metabolism in the (1)well-fed; (2)fasting and (3)starved state(over days to weeks)?
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| mazinger
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Here's a brief explanation..
Well fed state we have lots of glucose and other nutrients, glucose enters the liver (and pancreas) thorugh Glut-2 receptors, in the liver this glucose is metabolized in atp thorugh aerobic glycolisis and TCA & ETC.. when there is enough ATP in the liver it starts making Fatty acids from ACoa (which was obtained through PDH).. Fatty acids are packed with glycerol in VLDL and are exported to adipose tissue..
In Normal Fasting insulin levels are low wich activates hormone sensitive lipase which starts breaking stored fat in adipose tissue into glycerol and fatty acids. The fatty acids are packed in serum albumin and sent back to the liver. In the liver this fatty acids are broken down (B oxidation of fatty acids) into ACoa which is going to be used for atp syntheis (NOT to make glucose). When atp levels have reached a certain limit the liver "knows" that at this point it can do some work such as GLUCONEOGENESIS from lactate (Cori cycle), glycerol and alanine (alanine is obtained through protein catabolism thx to high glucagon levels). BE AWARE OF ONE THING all the new glucose that liver has synthetized (through glucogenolysis and gluconeogenesis) is NOT for its own metabolism, in fact it is ALL "secreted" to the blood for all the cells that have a TOTAL glucolitic metabolism such as RBCs and neurons.
In Starvation liver makes a similar work as in fasting, but is different in that protein catabolism is still active, but in a slower rate compared to normal fasting. An explanation for this is that we humans don't have a natural deposit of proteins. So protein catabolism is slowed down in order to preserve it. The liver starts making more ketone bodies than in normal fasting which at this point are going to be used not only by muscle, but also by the brain (Brain can switch its metabolism from nearly all glucolytic to one third glucolytic and two thirds from ketone bodies)..
Hope this helps.. If you need more info read kaplan biochem chapter 11
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| drk1980
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this was the brief version??? 
 thanks for this. im gonna read it atleast 5 times w/ short breaks to let it get thru my thick skin. goodluck.
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| mazinger
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Well yeah.. cause I didnt mention how metabolism is affected in deifferent organs and in different states.. according to lionel raymond understanding and integrating general metabolism is the most high yield section of all biochem! so be sure to master this! good luck!
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| STAYfocused
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| STAYfocused
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Hey,
Mazinger did a pretty good job in explaining it to you. I tried to add a rough time scale for you so it will be a little easier to comprehend. I had trouble writing all this in the post, so I just wrote it on a word document and attached it to this post. I hope it helps, and if you have any questions please feel free to ask.
SF
Attached Files:
METABOLISM.doc (35 KB, 21 downloads)
Edited by STAYfocused on 12/31/05 - 08:33 AM
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| drk1980
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thanks a lot for the efforts taken. even ur nickname at the foot end of every page helped a lot.
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