One of the functions of the cell membrane is to act as a 'partition'

• separating the cell contents from the fluctuating external environment 

• compartmentalising various areas within the cell (forming membrane-bound organelles), so that specific environments can be created for processes to occur effectively and efficiently

However, the cell and its organelles cannot work solely on its own, independent of its environment. As such, there must be movement across membranes.

Particularly for a cell, there must be transport across the cell membrane for the following reasons:

• to obtain nutrients

• to excrete waste substances

• to secrete useful substances

• to generate ionic gradients essential for nervous and muscular activity

• to maintain a suitable pH and ionic concentration for enzyme concentration

💡Types of transport across cell membranes

There are four basic mechanisms of transport, some are active (requiring extra energy from the expenditure of ATP) while others are passive (not requiring additional energy use).

The list below shows the mechanisms we will cover. Click on the mechanism to find out more about them.

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