Diffusion is the random movement of particles from areas of high concentration to areas of lower concentration. This happens because the particles in a liquid, solution or gas are able to move freely. The following video explains it quite nicely with a sugar lump dissolving in water as the example.
.
I will write about osmosis at some future point, which is the diffusion of water molecules across a semi-permeable membrane (that allows small molecules to pass through). It is powered by the same mechanism but is exclusively water molecules.
Cell membranes are selectively permeable – this means that they allow some materials through and not others. This nice video from Twig World about the role of the cell membrane ties these different points together. You will need to be logged into Twig to see this – ask if you don’t know how to do this.
Questions…
- In the sugar solution depicted in the first video, what is the solvent and what is the solute?
- What word means changing from a gas to a liquid?
- How would you describe the movement of particles in a solid?
- Apart from a cell membrane, suggest one other feature shared by plant and animal cells.
- What feature distinguishes eukaryotic cells from prokaryotic cells?
- Suggest a structure that you would expect to find in a typical plant cell that you would never find in a typical animal cell.
- Give one example of (a) a specialised plant cell (b) a specialised animal cell.
- Name a specific molecule that can cross a cell membrane by diffusion.
1. The solvent is the water and the solute is the sugar.
2. Condensation.
3. In constant motion close to each other. They move less than liquids and gases.
4. They both have a nucleus.
5. Prokaryotic cells such as bacteria do not have a nucleus.
6. Vacuole.
7. A) xylem cells.
B) fat cells.
8. Oxygen.
Thanks for another great post today!
Q1 – fantastic
Q2 – splendid
Q3 – hmm. We normally describe them as being in fixed positions so I don’t think we can say “constant motion” which implies that their location changes.
Q4 – indeed
Q5 – well done – they don’t have any organelles
Q6 – excellent
Q7 – good choices
Q8 – good
Nicely done! Check out tomorrow afternoon’s post for a reminder on particle behaviour in different states of matter.
1. solvent : water | solute : Sugar
2. Condensation
3. In motion
4. cytoplasm
5. One has no nucleus
6. chloroplasts
7. Specialised animal cell : Red blood cell | Specialised plant cells : root hair cell
8. Oxygen
Pictures of cat will come through email
Q1 – splendid
Q2 – indeed
Q3 – did you read the question correctly? This is about particles in a solid.
Q4 – well done
Q5 – if asked a question like this, make it very clear that you know which one has no nucleus (nor other organelles for that matter)
Q6 – terrific
Q7 – good work
Q8 – excellent
I am looking forward to seeing Feather – a lovely name! Can I post her picture on here?
Of course you may sir, at the moment she is hiding under the chair, so when she makes an appearance I will take a selfie with the “queen” of the house.