Explanation:
The endomembrane system (endo- = “within”) is a group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins. It includes a variety of organelles, such as the nuclear envelope and lysosomes, which you may already know, and the endoplasmic reticulum and Golgi apparatus, which we will cover shortly.
Although it's not technically inside the cell, the plasma membrane is also part of the endomembrane system. As we'll see, the plasma membrane interacts with the other endomembrane organelles, and it's the site where secreted proteins (like the pancreatic enzymes in the intro) are exported. Important note: the endomembrane system does not include mitochondria, chloroplasts, or peroxisomes.
Let's take a closer look at the different parts of the endomembrane system and how they function in the shipping of proteins and lipids.
