Courses for Kids
Free study material
Offline Centres

Endomembrane System

share icon
share icon

Endomembrane System : An Introduction

IVSAT 2024

The endomembrane system divides the cell into various organelles or compartments, including the nucleus, the endoplasmic reticulum (ER), the Golgi apparatus, and lysosomes. The ER gives rise to the endomembrane system, which then travels to the Golgi apparatus, where lysosomes develop. The ER is a continuous system of tubules and flattened membrane sacs that is designed specifically for lipid production and protein processing. For the compartmental arrangement of the cell to operate autonomously and correctly, the endomembrane system is critical. Consider yourself a pancreatic cell. It's your responsibility to release digestive enzymes, which enter the small intestine and aid in the breakdown of food's components.

Endomembrane System

Although the structure and function of each membranous organelle vary, they are all distinct from one another. Since their functions are coordinated, many of them are regarded as being part of an endomembrane system. Endoplasmic reticulum (ER), Golgi complex, lysosomes, and vacuoles are components of the endomembrane system. The mitochondria, chloroplast, and peroxisomes are not regarded as components of the endomembrane system because their functions do not overlap with those of the components mentioned above.

Endoplasmic Reticulum

A membranous structure called the endoplasmic reticulum is an important component of the endomembrane system of a eukaryotic cell that divides the intracellular space into luminal and additional luminal (cytoplasm) compartments.

Endoplasmic Reticulum Structure

Endoplasmic Reticulum

Endoplasmic Reticulum (ER)

Endoplasmic reticulum structure comes in two varieties: smooth endoplasmic reticulum and rough endoplasmic reticulum.

Rough Endoplasmic Reticulum Structure

  • Ribosomes are affixed to the cytoplasmic side of the membrane in rough ER. A collection of flattened sacs make up the rough ER. The lumen is the name of the area inside the ER.

  • The name comes from the fact that it is an attached flattened sac with a few ribosomes on its exterior.

  • It produces and releases chemicals, various compounds, and proteins in the liver and glands.

  • In cells that synthesize protein, rough ER is noticeable.

Functions of Rough Endoplasmic Reticulum

  • The majority of the rough ER components are involved in protein synthesis.

  • Additionally, the rough endoplasmic reticulum plays a significant role in protein folding.

  • Makes quality control in addition.

  • After protein synthesis and protein folding, protein organizing is the third most important ability.

Structure of the Smooth Endoplasmic Reticulum

  • On the other hand, ribosomes are absent from the smooth endoplasmic reticulum.

  • The tubular structure of the smooth endoplasmic reticulum is present.

  • It takes part in the production of phospholipids, which are the primary lipids in cell membranes and are necessary for digestion.

  • The Golgi apparatus, in particular, receives the outcomes of the rough ER's work from the smooth ER.

Function of the Smooth Endoplasmic Reticulum

  • The creation of vital lipids like cholesterol and phospholipids depends on smooth ER.

  • The release of steroid hormones is another function of smooth ER.

  • It is also in charge of glucose metabolism.

  • Calcium ions are stored and released by the smooth ER. Both the neurological system and the muscular systems depend on them.

Golgi Complex

Golgi complex

Golgi Complex

It is one of the endomembrane system's single membrane-bound organelles. The Golgi complex is mostly located in the cytoplasm of the cisternae, or membrane sacs, of eukaryotic cells. A Golgi stack has four to eight cisternae. The cis face and the trans face are the two faces of each Golgi stack. The entry face and exit face are additional names for both faces. Protein packaging and secretion are two of the Golgi apparatus' primary roles.


It is an organelle with a single membrane that houses hydrolytic catalysts for the disintegration of various biomolecules. Nucleases, proteases, lipases, glycosidases, phosphatases, phospholipases, and sulfatases are among the hydrolytic proteins included in this group. The molecule needs an acidic environment inside the lysosomes with a pH of roughly 5.0 for optimal action. There stays present a proton siphon inside the lysosomal layer. This proton siphon ships the proton from inside the film involving ATP as a wellspring of energy. Lysosomes are responsible for absorbing both intracellular and external materials because they can distinguish between infection particles or microorganisms during macrophage phagocytosis.




A vacuole is a membrane-bound structure that can be found in a cell's cytoplasmic membrane. Tonoplast is the name for the membrane that encases the vacuole. The vacuole's constituents, referred to as the cell sap, are distinct from the cytoplasm around it. Phospholipids are used to create layers. Proteins are injected into the layers to aid in the movement of molecules across the membrane. These proteins come in different combinations that help the vacuoles hold different matter.

Key Features

  • A membranous element of the eukaryotic cell is the endomembrane system.

  • A system of suspended membranous organelles is present in the cell's cytoplasm. Despite having various forms and activities, the organelles are referred to as a system since they are necessary for the proper operation of the cell.

  • The cell membrane, vacuoles, the nuclear membrane, lysosomes, the Golgi complex, vesicles, and the endoplasmic reticulum are all organelles that collaborate (ER).

Want to read offline? download full PDF here
Download full PDF
Is this page helpful?

FAQs on Endomembrane System

1. In the absence of lysosomes, how do plants protect themselves from bacteria? Or perhaps germs just don't harm plants?

  • In spite of the fact that plant cells have a separate defense mechanism, bacteria do assault plants. 

  • They include proteins that protect the plant from infection. 

  • When a pathogen infects a plant cell, the proteins attempt to stop it from entering the cell in the first place. 

  • The cell (or cells) must sacrifice itself, i.e., they must die and stop the infection from spreading deeper into the plant if that technique is unsuccessful and the pathogen is able to enter the cell.

2. What function does the endomembrane system serve?

  • The endomembrane system is what distinguishes eukaryotic cells from other types of cells. 

  • This system comprises four single membrane-bound organelles working in unison to package and transport things inside and outside. 

  • The endomembrane system enables a higher degree of cell specialization by allowing various components of the eukaryotic cell to be compartmentalized (for example, protein corruption occurs in the lysosome). 

  • The system depends on certain interactions between separate compartments, which are handled by trading between them via vehicles.

3. Why is there no endoplasmic reticulum in mature RBCs?

The most prevalent form of blood cells, red blood cells absorb oxygen from the lungs and release it as they pass through the body's capillaries. It helps the RBCs to hold more hemoglobin, which carries oxygen. The red blood cell can now carry more oxygen thanks to this. RBCs are responsible for delivering oxygen to every cell in the body, hence they must have a flexible shape that allows them to pass through capillaries with an extremely small diameter. As a result, they lose the ER, which other eukaryotic cells use as a skeletal structure. These cells can carry more oxygen more effectively because of the increased surface area caused by ER deficiency.

Competitive Exams after 12th Science