| Date | May 2012 | Marks available | 3 | Reference code | 12M.2.SL.TZ2.2 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 2 |
| Command term | Explain | Question number | 2 | Adapted from | N/A |
Question
The diagram (not to scale) shows a cell which contains water and sodium ions. This cell is immersed in a salt solution of water and sodium ions.
State the mode of transport if water moves into the cell.
State the mode of transport if sodium ions move into the cell.
Explain facilitated diffusion.
State the name of the structures formed within a cell by endocytosis.
Markscheme
osmosis
active transport
movement down the concentration gradient / from high to low concentration;
through channel proteins/ion channels;
passive transport / it requires no energy from the cell / no ATP;
for molecules that cannot pass through the phospholipid bilayer;
channel is specific/selective to the ion/molecule being transported;
vesicles / vacuoles / endosome
Examiners report
N/A
Candidates misinterpreted 2a(ii) as diffusion rather than active transport.
N/A
N/A
