Question 19M.2.SL.TZ2.5a
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.2.SL.TZ2.5a |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Outline | Question number | a | Adapted from | N/A |
Outline four types of membrane transport, including their use of energy.
[4]
a. simple diffusion is passive movement of molecules/ions along a concentration gradient ✔
b. facilitated diffusion is passive movement of molecules/ions along a concentration gradient through a protein channel «without use of energy» ✔
c. osmosis is the passage of water through a membrane from lower solute concentration to higher ✔ OWTTE
d. active transport is movement of molecules/ions against the concentration gradient«through membrane pumps» with the use of ATP/energy ✔ Active transport requires mention of the use of energy.
e. endocytosis is the infolding of membrane/formation of vesicles to bring molecules into cell with use of energy
OR
exocytosis is the infolding of membrane/formation of vesicles to release molecules from cell with use of energy ✔
f. chemiosmosis occurs when protons diffuse through ATP synthase «in membrane» to produce ATP ✔
The description of each type of transport should include the name and brief description.
mpa, mpb and mpc require reference to concentration.
Membrane transport – In spite of the question asking about energy, many lost easy marks by forgetting to refer to it. Others did not mention the gradients. In osmosis, please stress to the students which concentration they are talking about. They should be talking clearly about water potential or solute concentration.
