Structures and Functions in Living Organisms · 7 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 18% of your exam marks.
Aerobic and anaerobic respiration equations and comparisons are consistently tested.
Gas exchange and respiration are easy to confuse. To keep them separate:
A single-celled organism like Amoeba has a huge surface-area-to-volume ratio. Oxygen from the water can simply diffuse through its cell membrane straight into the cytoplasm fast enough to keep every part of the cell supplied. No special apparatus needed.
For a multicellular animal like a human, the inner cells of the body are far too deep for diffusion alone to supply them with oxygen at a useful rate. The body solves this by having:
Any good gas exchange surface, in any animal, has the same four adaptations: