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Glucose Metabolism- correct or is my understanding flawed?

  1. Feb 19, 2015 #1
    I am trying to understand about glucose metabolism! I have been researching this stuff forever! X(
    Would you see if my explanations are right, and if not, tell my why? Thank you SO much!
    That would be a HUGE help!
    1. Is it true that uptake and release of gas/nutrients only occur in the capillaries? (There is no gas or nutrient exchange going on in the veins or arteries, right?)
    2. Capillary uptake and release of gas/nutrients is only powered by diffusion, right?

    3. Do capillaries only use facilitated diffusion to take up or release glucose and simple diffusion for gas exchange?

    4. If facilitated diffusion is used, will there always be a lower concentration of glucose in the capillaries than in the interstitial fluid of villi?

      (That seems like the only way glucose could actually enter capillaries and not stay in the interstitial fluid...)

    5. From the villi capillaries, is glucose then transported by arteries until it ends up in a different capillary, where the interstitial fluid has a lower glucose concentration?

    6. If this is the case, does facilitated diffusion occur so that now the capillary and the interstitial fluid now have equal glucose concentration?

    7. Glucose in the interstitial fluid enters a nearby cell by facilitated diffusion?

    8. Will glucose always enter cells (except for intestinal cells) by facilitated diffusion because as soon as it does enter, glycolysis takes place to convert it to Acetyl-CoA- meaning there is never a build-up of glucose in the cell?

      (If ATP is needed, Acetyl-CoA undergoes TCA and the electron transport chain. If ATP is not needed (sedentary), excess Acetyl-CoA can be converted into adipose tissue.)
     
  2. jcsd
  3. Feb 19, 2015 #2
    Glucose gradients can be maintained via active transport. If facilitated diffusion were the only mechanism for glucose transport, that would mean that glucose would get transported in reverse the moment our intestines are empty of food.

    The biochemistry is more complex than instantaneous consumption (e.g. via glycolysis) maintaining a gradient between the intra- and extracellular environment. For example, the main glucose uptake system in bacteria is the phosphotransferase system (PTS) for active glucose uptake.
     
  4. Feb 19, 2015 #3
    I was saying that active transport does take place in the intestines, which you are confirming is correct? But I'm wondering how 1. glucose gets from interstitial fluid of villi into capillaries and 2. from capillaries to interstitial fluid between cells and 3. from interstitial fluid to cell interior.
    I thought 1, 2, and 3 were all by facilitated diffusion... If that's incorrect, why...?
    Thanks!
     
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