Yet another important cell organelle, the Endoplasmic Reticulum is really fascinating. We often talk about nucleus of a cell, the DNA, the RNA and ribosomes, the cell membrane and more. The attention that the Endoplasmic Reticulum gets is somewhat less that the other organelles of a cell. This isn’t fair because the Endoplasmic Reticulum is a highly specialized and complex organelle. It has a wide range of functions. In this article on Endoplasmic Reticulum facts, we are going to talk about its structure, its types and eventually read about its functions. We promise, it is going to be an interesting read. So, have some patience and read on…
Before You Read This: Consider Reading Our Article on Ribosomes. Understanding of Ribosomes Will Help You to Understand the Functions of Rough Endoplasmic Reticulum Properly. HERE IS THE LIST OF RIBOSOME FACTS.
Before we start, a quick look at this table will allow you to get some handy information that you can refer to whenever needed:
|True membrane bound||Yes|
|Present in||Eukaryotic cells (both plants and animals) except Red Blood Cells in mammals and spermatozoa|
|Absent in||Prokaryotic cells|
|Types||Smooth and Rough|
|Observed by||Albert Claude, Ernest Fullam and Keith Porter|
Now, let’s start…
Endoplasmic Reticulum Facts: 1-5 | What is Endoplasmic Reticulum?
1. It is an organelle of a cell. It is found only in Eukaryotic Cells. Eukaryotic Cells are types of cells that have a nucleus. So, Endoplasmic Reticulum is found in both animal and plant cells. In mammals however, this organelle is not present in Red Blood Cells and Spermatozoa.
2. Why such a name for the organelle? The name Endoplasmic Reticulum has two parts. The first part is derived from the term Endoplasm, which is the inner part of the Cytoplasm of a cell.
3. The second part, that is, Reticulum actually means ‘a fine network’. So, Endoplasmic Reticulum actually means a fine network present in the inner part of the Cytoplasm. The question is, ‘network of what?’
4. It is basically a network of Cisternae, vesicles and tubules. Cisternae are flattened sac-like structures that are enclosed in double membranes. Vesicles are transport sacs that operate inside a cell (intracellular). Tubules are minute or very small tubes.
5. Nearly 50% of the total Eukaryotic Cell surface is made of this particular organelle. It is the largest organelle in the cell.
High Suggest Read: 20 Cytoplasm Facts You Should Learn Today
Endoplasmic Reticulum Facts: 6-10 | Types and Structure of Endoplasmic Reticulum
6. When we speak of the structure of Endoplasmic Reticulum, we speak about the types first. However, if we are to speak about general structure then the Endoplasmic Reticulum is a network of Cisternae, Vesicles and Tubules.
7. This intricate network is very close to the nuclear membrane and from there, the network spreads out into the cytoplasm. The Endoplasmic Reticulum is sheathed in a membrane, which is a phospholipid membrane.
8. The double-membraned sac-like structures called Cisternae have tiny spaces (just like space inside a sac). These spaces are referred to as Cisternal Space or Endoplasmic Reticulum Lumen. This Cisternal Space or Endoplasmic Reticulum Lumen is continuous with the Perinuclear Space. (The Perinuclear Space in turn is the space between two lipid bilayers of the nuclear membrane. The two layers are called the Inner Nuclear Membrane and the Outer Nuclear Membrane. The space between the Inner and Outer Nuclear Membranes is called the Perinuclear Space.)
9. Points 6 to 8 give the general structure of the Endoplasmic Reticulum. However, in order to understand the structure of the organelle in details, we need to know that there are two morphological variants or forms of this organelle. They are:
- Smooth Endoplasmic Reticulum (often referred to as sER)
- Rough Endoplasmic Reticulum (often referred to as rER)
10. Both the sER and rER have the Cisternal Space or Endoplasmic Reticulum Lumen (ER Lumen). The ER Lumen is filled with a fluid, which makes up 10% of the total cell volume. The ER Lumen is kept separate from the Cytoplasm by the phospholipid membrane.
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