What is the pupose of phosphorylating glucose in cytosol?

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    • #1422
      bratwurst
      Participant

      hello !

      … there are tree possibilities:

      1) to trap glucose in cell
      2) destabilize glucose
      3) converts it into a better soluble form…

      who knows the answer ???
      for me all answerst sound great! … but which one is right?

      thx 😉

      bratwurst

    • #26363
      victor
      Participant

      I think the answer is (3).
      Glucose is phosphorylated become:
      Glucose-6-phosphate
      Fructose-6-phosphate
      Fructose-1,6-diphosphate
      then it converted into two molecules of:
      Phosphoglyseraldehyde
      1,3-diphosphogliserate
      3-phosphoglyserate
      2-phosphoglyserate
      Phosphoenole piruvic
      Piruvic acid——(2 molecules)

      then these two molecules of piruvic acid get in to oxidative decarbocillation and then Krebs.
      Hope this helps. 🙂

    • #26368
      bratwurst
      Participant

      biochemistry 5th stryer…

      (1) glucose 6-phosphate cannot diffuse through the membrane, because of its negative charge
      —> trapping glucose in cell

      (2) the addition of phosphoryl group begins to destabilize glucose…

      seems that the first two answers are right…

      but as you said the last answer seems
      to be right too:

      because it has a negative charge = polar ===> more soluble in aquaous environment???? is that right… so maybe all answers are right… LOL ….

      greetings 😉

    • #26371
      victor
      Participant

      Um…Glucose-6-phosphate doesn’t diffuse??well, I think that the phosphorilation of Glucose is changing glucose into 2 molecules of piruvic acid that have a smaller structure so they can diffuse through membrane..not making the glucose-6-phosphate and diffuse it right into membrane…I think the membrane that you’re talking about is the membrane of mitochondria right??

    • #26375
      bratwurst
      Participant

      hmm…. so only the 2 pyruvat molecules diffuse into the mitochondria… the glucose-6-phophate is trapped in cytosol….

      ok thx….

    • #26376
      Jelanen
      Participant

      The answer is 1. Glucose doesn’t diffuse through cell membranes, its transported. There is a transmembrane transporter for glucose, but not for glucose-1-P. Phosphorylating glucose locks it into the cell, preventing it from escaping. Adding a phosphate does nothing to help the solubility of glucose. A carboxyl group and 4 alcohol groups does that nicely. Yes, it does begin to destabilize the glucose, but its secondary to the locking it in the cell function.
      -Jelanen

    • #26389
      Poison
      Participant

      Answer: 1
      If you do not phosphorylate glucose, it can go out of the cell, but if you do it can not. Means you trap glucose.
      It seems that Jelanen gave a better answer. I promise I will read the posts before posting mine 🙂

    • #26440
      bratwurst
      Participant

      yes… lets say answer 1 is right 😉 ….

    • #26831
      MrMistery
      Participant

      Defiinetly answer no 1. The permease which transports glucose is so specific, that not only it can tell the difference between glucose and glucose-6-phosphate, but it can tell the difference between the optical izomers of glucose: D-glucose can pass, L-glucose can not pass…
      A little off-topic, but never the less very interesting

    • #28096
      xand_3r
      Participant

      Nice one MrMistery, but you can also say Please UGA of Please UAA. Glucose is actively transported everywhere in the organism, only pentoses (carbohydrates with 5 C atoms, eg ribose) are absorbed passively. Glucose absorbtion in the intestin is coupled with the Na transport , and it’s also totally reabsorbed in the proximal region of the urinifer tube. Phosphorilating glucose increases in a small way its solubility in polar solvents like water but it doesn’t have any effects on its solubility in the cell membrane wich is composed by phospholipids and its permeable only for liposoluble substances like cortisol and other cholesterol based hormones. Hidrosoluble substances like glucose can only pass through special protein tunnels, when they couple with specific receptors. So, like Jelanen said, phosphorilating doesn’t have any effects on the glucose solubility through the membrane, on the contrary it makes glucose unrecognizable for the specific receptors on the surface of plasmalema.

    • #28099
      sdekivit
      Participant

      another important thing to hold in mind is the before catabolism can occur, you must put energy in the to metabolizing molecule. This is done by converting glucose to fructose – 1,6 – bisphoshate. The the catabloism can occur, because the phosphate contains energy that can be stored for ATP-synthesis in the last step of the glycolysis. And what is the efficacy when you put some energy in converting a molecule if it’s wasted by simple diffusion out of the cell?

      Bt the answer to this question is, it can’t be said enough, answer 1.

    • #28100
      sdekivit
      Participant
      quote bratwurst:

      biochemistry 5th stryer…

      great book 😀

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