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Biology 2nd Baccalaureate

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6.9.1. Membrane systems

Endomembrane system

The eukaryotic cells have a endomembrane system of internal membrane which divides the cell into functional and structural compartments, called organellesThe prokaryotes have no endomembrane system and lack most organelles.

The endomembrane system also provides a transport system for mobile molecules through the interior of the cell, as well as interactive surfaces for lipid and protein synthesis. The membranes that make up the endomembrane system are built from a lipid bilayer, with proteins attached to each side or across them.

Fundamental Ideas About the Membrane System

The nucleus contains DNA and is transcribed into RNA, which is translated by ribosomes attached to the rough endoplasmic reticulum.

Proteins are synthesized by ribosomes located on the rough endoplasmic reticulum. As they are synthesized, they pass into the rough endoplasmic reticulum where the carbohydrate part will be added and a glycoprotein will begin to be synthesized.

The proteins synthesized are carried in vesicles to reach the cis face of the Golgi apparatus. Here, these proteins are transformed throughout their passage through the Golgi apparatus, depending on the role they are going to play, until they exit, through vesicles formed on the trans face of the Golgi apparatus, towards the plasma membrane, where the membranes and proteins exit the cell by secretion or exocytosis.


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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.