Question 19M.2.SL.TZ2.6a
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.2.SL.TZ2.6a |
| 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 ✔
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 ✔
mpa, mpb and mpc require reference to concentration.
Active transport requires mention of the use of energy.
Question 6 was the most popular extended response question. It was less common for students to correctly describe endocytosis and exocytosis. A common misconception was for students to describe both types of bulk transport as passive processes when they both require energy. Students also commonly failed to make reference to concentration gradients in their discussions of active and passive transport.
