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SingaporeCombined ScienceQuick questions
Biology: Cells and Human Physiology
Quick questions on Movement of substances: N(A)-Level Combined Science Biology
4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is diffusion?Show answer
Diffusion is the net movement of particles from a region where they are more concentrated to a region where they are less concentrated, down a concentration gradient. It happens because particles are always moving randomly, so over time they spread out evenly. Diffusion does not need energy from the cell. It is how oxygen enters cells and carbon dioxide leaves them.
What is osmosis?Show answer
Osmosis is a special case of diffusion that involves water. It is the net movement of water molecules from a dilute solution (lots of water) to a more concentrated solution (less water) through a partially permeable membrane. The membrane lets water through but not larger dissolved particles. Like diffusion, osmosis needs no energy from the cell.
What is the cell membrane?Show answer
The cell membrane is partially permeable: it allows some substances through while holding others back. This control lets the cell take in what it needs (such as oxygen and water) and remove waste, while keeping important contents inside.
What are effect of osmosis on cells?Show answer
What happens to a cell depends on the solution it is in:
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