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img089 - Click the Postabsorptive State Button 3—4 hours...

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Unformatted text preview: Click the Postabsorptive State Button: 3—4 hours after eating absorption of nutrients stops. The body now enters the postabsorptive state that is primarily a catabolic state. Energy needs are met by catabolizing stored glycogen, proteins and fats. ennui-mummy Pom-m m“ "d “M 5%” } Remember that the CNS relies on glucose as the energy 1 I l 1 source. The CNS can also use ketone bodies for energy W4: """"’ "‘" L” M” during extreme conditions (e.g. Starvation) but glucose is the preferred energy source. Primary function of the postabsorptive state is to maintain plasma glucose levels. W ,m be...“ A reduction in plasma glucose can impair brain function, '“V ”"'m “W” W” "‘ “'"W and result in loss of consciousness and death. Here are the main storage locations -— protein in muscle and other mom 1 cells (but remember that existing protein is functional :mfiwm and not actually stored); Glycogen is stored in muscle PRIORITY 2 and the liver; Triglycerides are stored in adipose tissue. rmnmmmmzmhwm mmammmm minion- bode. [E 3 Go to the next screen: So given the importance ofa continual supply of glucose to the CNS glucose must be made available for during the postabsorptive phase. The body synthesizes new glucose (gluconeogaiesis ) fi‘om breakdown products of catabolism. As well, most cells will switch their fuel preference to other energy sources, primarily fatty acids conserving the available glucose for the CNS; (called glucose sparing). Amino acids can be used by non-nervous tissue but is not a large source of fuel due to reasons we have already discussed. As is true in the absorptive state, cellular metabolism during the postabsorptive state differs among the types of cells. Adipocytes: In the postabsorptive state, triglycerides in adipose tissue are catabolized into glycerol and free fatty acids. Free fatty acids are released into the bloodstream as an energy sources for body cells. Glycerol is released into the bloodstream, travels to the liver where it is catabolized by glycolysis. mam m“ Cliek on the Liver Button: During the M um. min-I, mom-um mam postabsorptive state liver glycogen stores are Wm broken down by glycogcnolysis to glucose-6-P that is then catalyzed into glucose. Glucose is released am into the bloodstream for use by other cells. 1 ”in" a em” The liver can also make new glucose ”Mg (gluconeogenesis) from lactate that is transported w i mm W into the bloodstream for use by other cells in the \ body. Forty adds who ”my Some of the fatty acids are converted to ketone if“? bodies, released into the bloodstream and eventually catabolized by most tissues. Production I mm «m of ketones during prolonged fasting, frees the CNS reliance on glucose because it can acquires the ability to use ketones for energy. Click the Back Button Finally skeletal muscle cells: Glucose formed from glycogen during glycogenolysis here is used for energy only within that muscle cell. Glycogen is catabolized to glucose-6P but skeletal muscle cells lack the enzyme that catalyzes glucose—6—P to glucose. Glucose must be in its unphosphorylated form to be transported out of the cell. Thus the glucose formed by glycogenolysis in skeletal muscle cells remains in the cell and is catabolized by glycolysis to form pyruvate or lactate. Any lactate produced then travels to the liver for processing into glucose. Skeletal muscle cells can also catabolize proteins to amino acids, which are then transported into the bloodstream and carried to the liver for further processing. Click the Home Menu Button Page 3 of6 ...
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