9700 · 7.2
Transport mechanisms
Every living cell needs to control what goes in and out. This lesson breaks down the different ways cells transport substances, from tiny molecules diffusing passively to large particles being actively hauled using energy. Understanding these processes is key to how organisms function.
Need to know
What you need to know
- water moving thorough cells walls – apoplastic pathway.
- suberin deposits increase with age of endodermal cells except for certain passage cells.
- water can pass freely through these passage cells Image: By Dylan W. Schwilk - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=55396563.
- most water travels via the apoplastic pathway (when transpiration rates are high).
- these are the series of spaces running through the cellulose cell walls, dead cells, and the hollow tubes of the xylem.
- the water moves by diffusion as it isn’t crossing a partially permeable membrane.
- the water can move from cell wall to cell wall directly or through the intracellular spaces.
- movement of water via this pathway occurs more quickly than in the symplastic pathway.
Explanation
How cells move stuff around
- Review the structure of the cell surface membrane – it's crucial for understanding transport.
- Categorise transport into passive (no ATP) and active (requires ATP) processes.
- Memorise the key characteristics for each mechanism: gradient, proteins, energy requirement.
- Practise applying concepts to different cell types and scenarios, especially osmosis calculations.