Glucose Metabolism- correct or is my understanding flawed?

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SUMMARY

The discussion centers on glucose metabolism, specifically the mechanisms of glucose uptake and release in the human body. It is established that nutrient exchange occurs exclusively in capillaries, utilizing diffusion processes. Facilitated diffusion is the primary method for glucose transport from the interstitial fluid into capillaries, while active transport mechanisms also play a role in maintaining glucose gradients. The phosphotransferase system (PTS) is highlighted as a key active transport system in bacteria, contrasting with human glucose transport mechanisms.

PREREQUISITES
  • Understanding of glucose metabolism and its biochemical pathways
  • Knowledge of diffusion mechanisms, including facilitated diffusion and active transport
  • Familiarity with the structure and function of capillaries in nutrient exchange
  • Basic concepts of glycolysis and the TCA cycle
NEXT STEPS
  • Research the role of facilitated diffusion in glucose transport in human physiology
  • Explore active transport mechanisms in the intestines and their implications for glucose metabolism
  • Learn about the phosphotransferase system (PTS) in bacteria and its comparison to human glucose transport
  • Investigate the biochemical pathways of glycolysis and the conversion of Acetyl-CoA in energy metabolism
USEFUL FOR

Students of biochemistry, healthcare professionals, and anyone interested in understanding the complexities of glucose metabolism and its transport mechanisms in the human body.

Lo.Lee.Ta.
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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.)
 
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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.
 
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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