DP Biology (first assessment 2025)

Test builder »

Question 22M.2.SL.TZ2.a

Select a Test
Date May 2022 Marks available [Maximum mark: 4] Reference code 22M.2.SL.TZ2.a
Level SL Paper 2 Time zone TZ2
Command term Outline Question number a Adapted from N/A
a.
[Maximum mark: 4]
22M.2.SL.TZ2.a

Outline four different processes, with examples, that allow substances to pass through the plasma membrane.

[4]

Markscheme
  1. simple/passive diffusion down a concentration gradient / from high concentration to low concentration (without the use of channels/proteins); (e.g., CO2 / O2 / H2O / steroid hormones)
  2. osmosis is the diffusion of water from an area of high water potential / low solute concentration to low water potential / high solute concentration;
  3. facilitated diffusion is passive transport/diffusion through a protein channel; (e.g., glucose)
  4. active transport requires energy/ATP to move the molecules through a protein channel (e.g., Na-K pump / sodium potassium pump) against a concentration gradient/from low solute concentration to high concentration;
  5. endocytosis is the infolding of membranes to form a vesicle and take in a large molecule; (e.g., macrophages engulfing pathogens)
  6. exocytosis is the fusion of vesicles with membranes to release a large molecule; (e.g. neurotransmitters)
Examiners report

This question in section B was the second most commonly selected, but in performance, tended to do more poorly than the other questions.

Most candidates could list the processes that allow passage across the plasma membrane, but many answers lacked some of the necessary elements, most commonly leaving out examples (e.g. an example for gradient).

Syllabus sections