HELP!

[panicatthelunchbar]

Hi Guys,

does anyone have the activity manual for NoB? I can pm you or email you for it, please! it would be greatly appreciated

Also, how does glucose, starch, protein (albumin) travel through the plasma membrane? do they require energy or not?

Thanks

[shinny]

Hi Guys,

does anyone have the activity manual for NoB? I can pm you or email you for it, please! it would be greatly appreciated

Also, how does glucose, starch, protein (albumin) travel through the plasma membrane? do they require energy or not?

Thanks

Glucose goes through passive protein channels (no energy required) as well as active carrier proteins (energy required). As far as I'm aware, starch and albumin aren't transported through cell membranes. Quick Google searches seem to confirm this. They're both MASSIVE proteins molecules so I don't think it's possible. There isn't any need for cells to move them around really either. Starch is a storage protein molecule, so if other cells need energy, it'd get catabolised into glucose and shipped around accordingly. As for albumin, it's two purposes are basically to transport things within the blood (it's a universal carrier protein really which ships things around the body) as well as maintaining oncotic pressure within the blood (ignore this at your level - but basically it's a 'heavy-weight' solute which retains water within the blood). As such, there's no reason why albumin would go into a cell.

[panicatthelunchbar]

Starch is a protein?

[shinny]

Starch is a protein?

Whoops, polysaccharide I mean

[panicatthelunchbar]

And shinny, do you know where I can find the activity manual? I really need it!!

[shinny]

Would've helped if I did. I don't even know what it is, but I'm pretty sure the Biozone book is better.

[panicatthelunchbar]

Thank you so very much!

[panicatthelunchbar]

SHINNY! what do you mean by the albumin regulating the osmotic pressure?

[shinny]

SHINNY! what do you mean by the albumin regulating the osmotic pressure?

Ahah I said ignore it. Not worth explaining it since it'd probably confuse you slightly more if I gave a proper explanation.

[panicatthelunchbar]

Ok, thanks. Also if you could help me out with this too:

We put 5% albumin solution in a dialysis tube and sealed it. Then we put in a beaker with water solution. Albumin didn't move into the water, as predicted, but water didn't travel into the albumin solution either. Why is that?

Sorry, im bombarding you with questions :/

[shinny]

Ok, thanks. Also if you could help me out with this too:

We put 5% albumin solution in a dialysis tube and sealed it. Then we put in a beaker with water solution. Albumin didn't move into the water, as predicted, but water didn't travel into the albumin solution either. Why is that?

Sorry, im bombarding you with questions :/

Depends on the quantities of water. If you put just the right amount, the hydrostatic pressure (i.e. effect of the weight of water itself) could balance things out. This obviously isn't something you're meant to know in unit 3 though.

From a unit 3 point of view, we know that water can pass through the semi-permeable membrane (dialysis tubing) but albumin can't. This means that the albumin solution (5%) is hypertonic to the beaker solution (distilled water 0% I imagine), meaning that water should flow from the beaker into the dialysis tube. Since this hasn't happened, you could blame experimental errors and such. Has your teacher said that this is the expected result as of yet? Otherwise hydrostatic pressure is all I can think of. I'll need more specific details about the set up of the experiment to get a good idea really..

[panicatthelunchbar]

well we used 4 solutions to put inside the tubing: water, starch, glucose, and albumin.
glucose was the only solution that was transported through the tubing into the solution of water outside- as you said earlier this is justifies as glucose only needs passive transport to travel through a membrane and maybe thats why it leaked out into the surrounding solution.

Although albumin wouldn't be expected to come out into the water in the beaker, wouldn't the water in the beaker be expected to move into the albumin solution in the dialysis tubing? because of osmosis, there is high solute concentration inside the tubing than there is outside, so water should've moved in, but there was no change! the teacher said our results were perfect :/

[shinny]

But how was the actual tubes and beaker set up? For example, in something like this, you'd expect gravity to do something. If there was no solutes for example, obviously you expect water from the right side to go to the left and equalise the water level on both sides. However, since there are solutes and water is trying to go to the left side to dilute the solutes that are there, both sides are going to be uneven. There's a pushing force to the left due to osmotic forces, but a pushing force to the right due to hydrostatic pressures (gravity). That's the only explanation I can think of for your scenario, but it's way outside the scope of unit 3. Plus, if your's is set up the way that I think it is (a tube just floating inside a beaker of water), I'm not sure how the whole gravity thing works actually.

[panicatthelunchbar]

we used a rhetort stand and clamp set-up. so the dialysis bag was tied to the clamp on the stand and hung down into a beaker full of water. the water covered the entire dialysis tube thing.