The Endoplasmic Reticulum

The Endoplasmic Reticulum (ER) is a very amazing part of the cell! (Well I guess every part of the cell is amazing if you see all of what it does). It is responsible for a wide range of tasks! Including the biosynthesis of: lipids for constructing new membranes, proteins (via ribosomes) and complex carbohydrates. The ER membrane typically makes up more than half of the total membrane in the cell and is located between the nucleus and the cytosol and specifically the golgi apparatus. This means that there are 2 membranes between the nucleus and the Golgi Apparatus, the outside ER membrane and the nuclear membrane (This is because the ER is continuous with the outer nuclear membrane). However, there are 2 membranes between the golgi and the ER and there is a LARGE amount of transfer between the two organelles, which suggests there is probably transport occurring through transport vesicles (shown below).

The ER is a made up of two phospholipid bilayer membranes. The enclosed 'sac' is called the ER lumen, the internal space of the ER. The ER is thought to be a single continuous membrane (Reference). Also there are two types of ER:

Rough ER: Is associated with ribosomes (the dots on its boundaries) and the membranes tend to be in 'sheets' or flatten sacs called cisternae.

Smooth ER: Which lacks ribosomes, and is also more of a mesh of smaller interconnecting tubes.

The Endoplasmic Reticulum:

Go to Chapter 2.2.2: 'Mitochondria/Chloroplasts'

WWW Cell Biology Course Index

Go to: Chapter 2.2 Index: 'Internal Organelles/membranes'.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.