BRAINCAKEGas Exchange in Unicellular Organisms
Single-celled organisms have a large surface area to volume ratio because they are small. They can therefore exchange substances with their environment by simple diffusion.
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Key terms in this lesson
- prokaryotic cell
- A cell with no nucleus or membrane-bound organelles, found in bacteria.
- diffusion
- The net movement of molecules or ions from a region of higher concentration to a region of lower concentration, down a concentration gradient.
- surface area to volume ratio
- The ratio of an organism's outer surface area to its volume; it decreases as size increases, which limits the rate of exchange achievable by diffusion alone.
More in Exchange Surfaces and Breathing
- The First Breath
- Measuring Lung Capacity
- Lung Volume
- Breathing Rate and Ventilation Rate
- Gas Exchange in Insects
- Diffusion Gradient
- Mass Transport
- Increasing the Rate of Diffusion
All 24 lessons in Exchange Surfaces and Breathing · All OCR AS-level Biology topics