Question 19M.3.SL.TZ1.1c
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.SL.TZ1.1c |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Membrane structure can be investigated using a technique known as freeze fracture.
Cells are frozen and then split. Fracturing often occurs between the two phospholipid layers of membranes in the cell. An electron micrograph of such a fractured membrane is shown.
[Source: © Science Photo Library]
Explain how the amphipathic nature of phospholipids allows them to form bilayers.
[2]
a. amphipathic means that they are both hydrophilic and hydrophobic ✔
b. the outside hydrophilic parts are exposed to water ✔
c. hydrophobic parts are away from water in the inside ✔
Water or lack of needs to be mentioned for mpb
The terms hydrophilic and hydrophobic were commonly stated, although sometimes assigned to heads and tails incorrectly; however this was not penalised. Orientation towards or away from water was less often explained.
