What is the Difference Between Cisternae and Tubules

The key difference between cisternae and tubules is that cisternae are present in the rough endoplasmic reticulum (RER) while tubules are present in the smooth endoplasmic reticulum (SER).

The endoplasmic reticulum is a network of membranes present inside the cell. ER carries out different functions in the cell, including modification and movement of molecules like proteins. There are two types of ER depending on the presence of ribosomes. Rough endoplasmic reticulum is the type that contains ribosomes. ER without any ribosomes is called the smooth endoplasmic reticulum. Cisternae and tubules are the two distinct regions in the rough endoplasmic reticulum and smooth endoplasmic reticulum, respectively.

CONTENTS

1. Overview and Key Difference
2. What are Cisternae 
3. What are Tubules
4. Similarities – Cisternae and Tubules
5. Cisternae vs Tubules in Tabular Form
6. Summary – Cisternae vs Tubules

What are Cisternae?

Cisternae are membrane-bound sacs present in both the endoplasmic reticulum and Golgi apparatus, which participate in the packaging and modification of proteins. Cisternae appear in two different formats in the endoplasmic reticulum and Golgi apparatus. In the rough endoplasmic reticulum, cisternae appear as flattened sacs on the branch, and in the Golgi apparatus, they appear as curved sacs. The cytoskeleton of the cell provides the shape for the cisternae. Protein modification and packaging is the main function of cisternae due to the presence of ribosomes in the rough endoplasmic reticulum. The number of cisternae stacked in the Golgi apparatus depends on the cell type and the organism.

Cisternae vary by function, structure, and composition within each Golgi stack. Hence, they are categorized into three groups: cis Golgi network, medial, and Trans Golgi network. When proteins move through the cisternae, modifications such as phosphorylation, glycosylation, and cleavage occur, creating different functional channels. Cisternae possess different enzymes to facilitate protein modifications and guide the modified proteins to their final destinations.

What are Tubules?

Tubule is the main unit present in the smooth endoplasmic reticulum, which forms fine disc-like tubular membrane vesicles. Tubules present in the smooth endoplasmic reticulum are involved in the synthesis and storage of lipids (phospholipids and cholesterol) that involve in the synthesis of new cell membranes.

Depending on the type of cell, these tubules possess different functions. In some cell types, such as in adrenal glands, the tubules of the smooth endoplasmic reticulum involve in the synthesis of steroid hormones from cholesterol. Similarly, in the liver, enzymes present in the tubules catalyse detoxification processes of metabolic waste and chemical water-soluble waster through drug rendering. The tubules present in the skeletal muscle present as a specialized membrane structure known as sarcoplasmic reticulum, which acts as a storage site for calcium ions.

What are the Similarities Between Cisternae and Tubules?

• Cisternae and tubules are present within eukaryotic cells.
• Moreover, both are located in association with the endoplasmic reticulum.
• They are involved in the synthesis of different molecules.
• Both cisternae and tubules provide passage for the movement of different molecules to their pre-defined destinations.
• Both are involved in the packaging of synthesized or modified molecules.

What is the Difference Between Cisternae and Tubules?

The key difference between cisternae and tubules is that cisternae are present in the rough endoplasmic reticulum (RER) while tubules are present in the smooth endoplasmic reticulum (SER). Moreover, cisternae are involved in the packaging and modification of proteins, while tubules are involved in the synthesis and storage of lipids.

The below infographic presents the differences between cisternae and tubules in tabular form for side by side comparison.

Summary – Cisternae vs Tubules

Endoplasmic reticulum is an important organelle involved in different functions in eukaryotic cells. Cisternae and tubules are the two distinct regions in the rough endoplasmic reticulum and smooth endoplasmic reticulum, respectively. The key difference between cisternae and tubules is that cisternae are found in the rough endoplasmic reticulum (RER) while tubules are found in the smooth endoplasmic reticulum (SER).

Reference:

1. “Smooth Endoplasmic Reticulum: Definition, Function & Structure.” Biology Dictionary, 5 Oct. 2019.
2. “Rough Endoplasmic Reticulum Definition & Meaning.” Merriam-Webster, Merriam-Webster.

Image Courtesy:

1. “0314 Golgi Apparatus a en” By OpenStax – from the Textbook OpenStax Anatomy and PhysiologyPublished May 18, 2016 (CC BY 3.0) via Commons Wikimedia
2. “Figure 04 04 02” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia