Energy source Q

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Energy source Q

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drk1980
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01/14/06 - 12:35 PM

At what point does the body switch from predominantly protein metabolism to using fat as a primary energy source?
1. 24 hours
2. 72 hours
3. 1 week
4. 2 weeks

msyamp
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01/14/06 - 01:19 PM

4?

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anjushree
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01/14/06 - 01:21 PM

1 week

drk1980
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01/15/06 - 12:32 AM

24 hrs- glycogenolysis exhausted, gluconeogenesis
72hrs- gluconeogensesis continues
1week- switches to ketogenesis

anjushree, u got the answer to this Q! btw whats ur reference? i thot the timescale ws a lil ambiguous.

msyamp
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01/15/06 - 01:05 AM

thanks drk

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STAYfocused
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01/16/06 - 01:01 PM

drk1980 wrote:
At what point does the body switch from predominantly protein metabolism to using fat as a primary energy source?
1. 24 hours
2. 72 hours
3. 1 week
4. 2 weeks

Was this an actual question from a book?

I don't understand why it would take fat so long to become the primary energy source. I'm looking at the lippincott graph, and gluconeogensis peaks around 36 hours and begins to decline after that. After 72 hours it has really dropped, so wouldn't fat begin to take over then?

Maybe it has something to do with the amount of glucose our body utilizes in an hour. Does anyone know the total amount of glucose in grams our body needs to carry out normal functions?

msyamp
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01/16/06 - 01:08 PM

yes it takes long to switch to ketogenesis. because before aweek it is gluconeogenesis. but later after excess protein is sent. then liver will totally depend on fatty acids to produce ketones. BTW brain depends purely on ketones after several weeks. that means till several (4) weeks there some source of glucose that is gluconeogenesis. or odd carbon chain fatty acids producing propionyl co A. it think the rbc mass which is not stong enough to make energy from ketones wil get energy soley from oddcarbon fatty acid and gluconeo from their genie servant the liver

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drk1980
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01/16/06 - 01:20 PM

yea it is an actual Q. The explanation to it i hv given above. It had me wondering too abt the timescale. Altho for different reasons.
The Q asks abt the time when energy source SWITCHES to PRIMARILY fat metabolism. So at 72 hours fat has probably begun to be used but at 1 week(as this Q says) it is entirely dependant on fats.
i used to think it was 2-3weeks.

Iam not aware of any one value for the normal funcational blood glucose level...IMO its a range. anyway below 60mg/dl there will be appearance of signs of hypoglycemia. The value for hypoglycemia is 40mg/dl though.

STAYfocused
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01/16/06 - 01:45 PM

drk1980 wrote:
yea it is an actual Q. The explanation to it i hv given above. It had me wondering too abt the timescale. Altho for different reasons.
The Q asks abt the time when energy source SWITCHES to PRIMARILY fat metabolism. So at 72 hours fat has probably begun to be used but at 1 week(as this Q says) it is entirely dependant on fats.
i used to think it was 2-3weeks.

Iam not aware of any one value for the normal funcational blood glucose level...IMO its a range. anyway below 60mg/dl there will be appearance of signs of hypoglycemia. The value for hypoglycemia is 40mg/dl though.

Thanks for the replies - Mysamp and Drk1980.

This whole time scale is pretty confusing for me, I don't know any book that really does a good job in explaing it, but I think I pretty much have it down now.

Good question BTW! 1 Less error I will make on the boards. LOL

anjushree
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01/17/06 - 12:27 PM

#10

kaplan graph in lipid metabolism chap

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