Rough Endoplasmic Reticulum (RER) — Structure & Function

Ballad of the Rough ER

The endoplasmic reticulum has folded membrane stuff

That can be smooth or can be rough.

While both can take part in similar things

The rough ER has ribosomes that cling

To the membrane, looking like bumpy lumps.

The ribosomes on the membrane make new proteins in loose clumps

That are folded in the smooth ER, made neat instead of shoddy

And those proteins are shipped to the Golgi body.

What Is the RER?

The rough endoplasmic reticulum (also called the RER), is an organelle found in both animal and plant cells. It is made up of interconnected, flattened membrane sacs. It's also attached to the nuclear membrane, which contains the nucleus. This connection lets important molecules travel directly from the nucleus to the RER.

What Does It Do?

The RER is responsible for protein synthesis, modification, packaging, and quality control.

We say that the RER makes proteins, but actually most of this is done by the ribosomes attached to its surface. These are called membrane-bound ribosomes.

One key point to remember is that the RER makes secretory proteins only. These are the proteins that will be shipped out of the cell once they are complete. Proteins that will remain in the cell after synthesis are made by free ribosomes—those that are not attached to the RER.

Protein Synthesis

The process of protein synthesis begins when the information in DNA is read and transcribed. Short strands of messenger RNA (mRNA) carry the information from the nucleus to the ribosomes on the RER, where it can be used to synthesize proteins. At the ribosome, different amino acids which correspond to the mRNA sequence are connected together to form long chains. These chains are pushed into the RER, where they can be modified, folded, and checked for errors before becoming functional proteins.

After this, a part of the RER membrane which contains the complete protein will pinch off, forming a vesicle. The vesicle can take the protein to wherever it's needed.

Function of the Rough ER

The rough endoplasmic reticulum (better known as the rough ER or the RER) is a bunch of connected, flattened sacs that help fold up the proteins made by ribosomes during protein synthesis.

This is convenient because the surface of the RER is studded with ribosomes. In fact, that's what makes it rough.

The RER is found in eukaryotic cells. It receives proteins made by the ribosomes. These proteins aren't quite finished though. At this point, they are just chains of amino acids. As these chains pass through the connected, flat sacs of the RER, they are folded up and modified.

The RER then passes the folded proteins on to the Golgi body. The Golgi body finishes things by shipping the completed proteins around the cell.

Key Vocabulary:

1. Rough endoplasmic reticulum
2. Ribosome
3. Protein
4. Protein synthesis

The rough endoplasmic reticulum is a network of membranes called cisternae, which are held together by the cytoskeleton. The membranes are covered in ribosomes, much like those studded belts from the early 2000s.

As proteins leave the ribosomes after translation, the rough ER (RER) takes them and modifies them. These proteins are then moved to another organelle, called the Golgi apparatus, which exports them to a specific location in the cell or even outside of the cell via the cell membrane.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Vacuole}}$ : Organelle that contains water and nutrients. Refrigerator of the cell

$\color{#8925AE}{\text{Golgi Apparatus}}$ : Stores, sorts, and modifies proteins and lipids. Post office of the cell

$\color{#8925AE}{\text{Cytoskeleton}}$ : Helps the cell maintain its shape and assists with movement. Skeleton of the cell

$\color{#8925AE}{\text{Mitochondria}}$ : Makes ATP (energy). Powerhouse of the cell

$\color{#8925AE}{\text{Ribosome}}$ : Creates polypeptide chains and proteins. Factory of the cell

$\color{#8925AE}{\text{Endoplasmic Reticulum}}$ : The smooth ER makes lipids for the cellular membrane. The rough ER assembles proteins and transports them into and out of the cell

$\color{#8925AE}{\text{Nucleus}}$ : Contains the genetic material, DNA, of the cell. Brain of the cell

(Video) Intracellular Organelles – Rough Endoplasmic Reticulum

by Medic Tutorials

This video explains what the rough endoplasmic reticulum does, what parts it has, and how it interacts with the rest of the cell.