The appearance, ultrastructure and function of endoplasmic reticulum.

Endoplasmic reticulum (ER) provides a surface for the synthesis of different molecules needed in a cell. It can also store and transport these materials.

The molecules involved depend on the type of ER:

• Rough endoplasmic reticulum (RER) makes and transport proteins and glycoproteins; it has ribosomes on its surface because they are involved in protein synthesis.
• Smooth endoplasmic reticulum (SER) stores, transports and synthesises lipids and carbohydrates.

ER is sometimes continuous with (attached to) the nucleus of a cell.

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ER is made up of 'flattened sacs' called cisternae surrounded by a membrane. Both types are complex structures but SER looks more tubular compared to the 'liney' RER.

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