VCE Biology Question Thread

[Gogo14]

I have my Bio SAC tomorrow on the plasma membrane. We did an experiment with dialysis tubing. We put a dialysis tube filled with Solution A (containing glucose, starch, Na+ and Cl-, and proteins) into a beaker of distilled water and let it sit for 30 minutes. Before that, we tested the concentration of the glucose, starch, Na+ and Cl-, and protein both inside and outside the tube. After 30 minutes we tested it again.
So this was the experiment we did.
Anyone have any idea what sort of questions could be asked about this?

Thanks so much

EDIT: Also, I'm pretty sure "write a conclusion" will be a question asked tomorrow, does anyone know how to structure a good conclusion? It's the one part of a prac report I find the hardest!

My school is doing the exact same prac lol. I' m the same boat, but I think they will ask a lot about diffusion and osmosis. For a conclusion, you say whether the aim have been achieved or not, what the results show, and if it supports the hypothesis or not.

[Photon]

I have my Bio SAC tomorrow on the plasma membrane. We did an experiment with dialysis tubing. We put a dialysis tube filled with Solution A (containing glucose, starch, Na+ and Cl-, and proteins) into a beaker of distilled water and let it sit for 30 minutes. Before that, we tested the concentration of the glucose, starch, Na+ and Cl-, and protein both inside and outside the tube. After 30 minutes we tested it again.
So this was the experiment we did.
Anyone have any idea what sort of questions could be asked about this?

Thanks so much

EDIT: Also, I'm pretty sure "write a conclusion" will be a question asked tomorrow, does anyone know how to structure a good conclusion? It's the one part of a prac report I find the hardest!

Do you think that the Na+ and Cl- would form salt? considering they are left there without energy being added.

[Arithmetic]

Hi all!

Why does adding methylene blue stain allow us to view cells more clearly?

Thank you.

[geminii]

Do you think that the Na+ and Cl- would form salt? considering they are left there without energy being added.

I did ask my teacher this, she said they diffuse through the membrane separately.

Another question... Can anyone lost what substances diffuse into and out of human cells through: a) active transport b) simple diffusion and c) facilitated diffusion.
Thanks again guys!!! 😊

[Photon]

I did ask my teacher this, she said they diffuse through the membrane separately.

Wait what, how would they diffuse through if they are ions? Doesn't a dialysis tubing act like a phospholipid bilayer?

[sunshine98]

I have my Bio SAC tomorrow on the plasma membrane. We did an experiment with dialysis tubing. We put a dialysis tube filled with Solution A (containing glucose, starch, Na+ and Cl-, and proteins) into a beaker of distilled water and let it sit for 30 minutes. Before that, we tested the concentration of the glucose, starch, Na+ and Cl-, and protein both inside and outside the tube. After 30 minutes we tested it again.
So this was the experiment we did.
Anyone have any idea what sort of questions could be asked about this?

When I had a similar SAC back last year there were questions about :
-hypothesis
-explaining  the results (that is , using words such as osmosis etc)
- Variables (controlled, independent and dependent)
- Which is the controlled group and which is the experimental?
Basically things like that

Another question... Can anyone lost what substances diffuse into and out of human cells through: a) active transport b) simple diffusion and c) facilitated diffusion.
Thanks again guys!!! 😊

I cant really list every substances that goes through using these methods because I don't know  , but if a question were to come up it would hint to you something about the structure that you could use to decide which method.
Eg: if it were saying that the substance is large and hydrophilic and it was going along the concentration gradient , you would know that it must undergo facilitated diffusion.
But nonetheless I will tell you the main things with some examples
-Simple diffusion : small molecules , hydrophobic/lipophilic, uncharged, nonpolar (eg: O2 , urea)
- Facilitated diffusion: large molecules , hydrophilic/ lipophobic , charged , polar
-Active transport :for this one , it is ANYTHING going against the concentration gradient

Why does adding methylene blue stain allow us to view cells more clearly?
Thank you.

Idk if you mean how stains work, in which case  am pretty sure that you don't need to know . But if you mean why we stain things it mainly cause  most organelles are colourless/ transparent so you need to stain them to actually see them and make them distinct from the rest of the cell.

[geminii]

I cant really list every substances that goes through using these methods because I don't know  , but if a question were to come up it would hint to you something about the structure that you could use to decide which method.
Eg: if it were saying that the substance is large and hydrophilic and it was going along the concentration gradient , you would know that it must undergo facilitated diffusion.
But nonetheless I will tell you the main things with some examples
-Simple diffusion : small molecules , hydrophobic/lipophilic, uncharged, nonpolar (eg: O2 , urea)
- Facilitated diffusion: large molecules , hydrophilic/ lipophobic , charged , polar
-Active transport :for this one , it is ANYTHING going against the concentration gradient

Thanks so much! But do you have any examples for facilitated diffusion and active transport? That would be really helpful!! Thanks heaps again!!

[sunshine98]

Thanks so much! But do you have any examples for facilitated diffusion and active transport? That would be really helpful!! Thanks heaps again!!

Sorry , didn't realise that I didn't give example for facilitated. An example could be glucose (its very large and very polar)
As I said for active transport it can be anything. If glucose needs to be taken in against the concentration gradient it will undergo active transport so  it could technically work as an example. If Na needed to be taken in against the concentration gradient it would be active transport so it would also work as an example. That's why I'm saying it could be anything , as long as its against the concentration gradient.

[poppingsoda]

Link the structure of the membrane with its function:
The plasma membrane is composed of a phospholipid bilayer with various proteins embedded into it. The plasma membrane holds the cell together and provides a semi-permeble barrier.

Would this be a sufficient response?

[cosine]

Link the structure of the membrane with its function:
The plasma membrane is composed of a phospholipid bilayer with various proteins embedded into it. The plasma membrane holds the cell together and provides a semi-permeble barrier.

Would this be a sufficient response?

Wonderful answer, but the cellular membrane does not hold the cell together, the cytoplasm and cytoskeleton do. The cell membrane is indeed a phospholipid bilayer, which separates the internal environment from the extracellular fluids. Because it says structure and not chemical nature, I think this would be the best answer.

[sunshine98]

Link the structure of the membrane with its function:
The plasma membrane is composed of a phospholipid bilayer with various proteins embedded into it. The plasma membrane holds the cell together and provides a semi-permeble barrier.

Would this be a sufficient response?

Idk if I'm interpreting the question a bit differently but wouldn't it be better if you explained how the structure enables it to effectively accomplish its function. Like how the phospholipid molecules act as effective barriers due to their amphipathic-ness etc

[vox nihili]

Idk if I'm interpreting the question a bit differently but wouldn't it be better if you explained how the structure enables it to effectively accomplish its function. Like how the phospholipid molecules act as effective barriers due to their amphipathic-ness etc

I'm inclined to agree

[poppingsoda]

Idk if I'm interpreting the question a bit differently but wouldn't it be better if you explained how the structure enables it to effectively accomplish its function. Like how the phospholipid molecules act as effective barriers due to their amphipathic-ness etc

Thanks for your response, I was actually unsure what the question was asking.

[vox nihili]

Thanks for your response, I was actually unsure what the question was asking.

As sunshine98 said, this question is a really clear invitation to describe the structure of the membrane as a phospholipid bilayer and explain that, by virtue of its chemical structure, the bilayer acts as a semi-permeable barrier.

[gameboy99]

Hey could somebody give an explanation of what is osmotic pressure and give a definition of it as well???