ENDOPLASMIC RETICULUM
Endoplasmic reticulum is a single-membrane-bound organelle. The endoplasmic reticulum is a network of highly branched tubular and microsomal vesicular structures that are interconnected.
One end is connected to the nuclear membrane whereas the other end connects to the plasma membrane. It is often termed the ‘system of membranes.’ It is covered by a limiting membrane formed by bilayered lipids and proteins. The endoplasmic matrix is a fluid material found in the lumen of the endoplasmic reticulum. The diameter of the lumen is between 400 to 700A. The endoplasmic reticulum maintains the link between the nucleus and cell membrane.2.4.1 Types of Endoplasmic Reticulum
There are two types of endoplasmic reticulum: rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). Both the types are interconnected and continuous with each other. The rough endoplasmic reticulum transitions to smooth endoplasmic reticulum and vice versa depending upon the activities of the cells,
This roughness is why it is referred to as the granular endoplasmic reticulum. Additionally,
Rough endoplasmic reticulum or RER
Ribophorins (glycoproteins) aid in the attachment of ribosomes to their surface, resulting in a rough appearance.
This roughness is why it is referred to as the granular endoplasmic reticulum.
It plays a crucial role in the active synthesis of proteins and secretion processes, such as in the goblet cell of the liver.
It is extensively connected and continuous with the outer membrane of the nucleus.
Eg: Adipose tissue, Muscle
Smooth endoplasmic reticulum or SER
In the absence of ribosomes, they exhibit a smooth surface.
The smooth endoplasmic reticulum displays a sleek appearance and is alternatively known as agranular reticulum.
SER is responsible for producing lipids, visual pigments, and steroids, as well as storing them. Additionally, it plays a role in detoxifying harmful drugs.
Smooth muscles contain a specialized structure of SER known as the sarcoplasmic reticulum, which plays a crucial role in muscle contraction.
Eg. Liver, Pancreas
2.4.1.2 Functions
1. The endoplasmic reticulum (ER) functions as the cytoskeleton, offering structural support and maintaining the shape of the cell.
2. The RER supplies precursor molecules of lysosomal enzymes to the Golgi apparatus.
3. The smooth endoplasmic reticulum is involved in the production of lipids and steroid hormones.
4. RER are actively participating in protein synthesis and secretion.
• Intracellular exchange - The endoplasmic reticulum (ER) forms an intracellular conducting system. Material transport within the cytoplasm can take place through the ER.
• Detoxification - The Smooth ER is primarily responsible for the detoxification of drugs, pollutants, and steroids.
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