Appendix 4

Example of critical features identified from students’ interpretation of the diagram.

The following citation from the third-year university student Johanna’s explanation of the still image shows that the image can convey the critical features A and B:

J: It looks like some kind of transport proteins in a cell membrane…

I: And how can you see that it is a cell membrane?

J: You can see it from these small phospholipids here with rings and two lines which constitute a double layer… [I:Mm] It’s like… You have seen it a thousand times… these simple things… a ring with two lines… then you know it right away.

I: Mm, and what is the explanation why they form this kind of structure?

J: It is related to hydrophobic and hydrophilic properties… that these polar, round parts are turned outwards and inwards the cell, where there is water, and then there are the hydrophobic parts, which are turned inwards, towards each other…

The following citation from Jan, a third-year university student, shows that the critical feature C can be identified from the still image:

J: We can see different kinds of transport proteins in the cell membrane.They transport substances in and out of the cell.

I: If you look at these three… you can see that there are some differences. Can you see from the picture what the difference is between these?

J: Yeah… the one to the right demands energy to transport this substance out of the cell, because ATP adds energy… In the case of the one to the left, I think it just flows freely, because it is an open channel.

I: What decides how the substance flows?

J: Well… It can be some kind of pH-gradient or electrical gradient, or electrochemical gradient… I suppose it is because of some kind of attraction force, either the concentration or charge which attracts them. And the one in the middle needs some kind of conformational change to let the substance in.

I: Is that an active or passive transport?

J: It doesn’t seem to require any energy, so it is probably passive.

I: If you look at their direction of movement… can you from the picture see what make them move…?

J: Yes, there is a higher concentration outside the cell, so they are inclined to diffuse into the cell, while it requires energy to transport them in the other direction, against the gradient.

In the following quote from Cecilia, in her third year of upper secondary education, we can identify the critical features 1) Extrapolation between 2D and 3D and 3) The complexity of molecular interaction:

C: […] I think it’s tremendously complex. Sure, I can understand this… but I can’t understand it in relation to the whole.

I: Can you give an example of something that helped to explain?

C: It was that computer thing… that animation you showed […] that it shows 3D… Here something gets in… then the next clings on… Because it’s easy to divide it into smaller parts, so it becomes difficult to see the connections between different things. Maybe the text book could explain better how the different things connect to each other.