What is the Difference Between Cell Membrane and Nuclear Membrane

The main difference between cell membrane and nuclear membrane is that cell membrane is the biological membrane that separates the interior of all cells from the outside environment whereas nuclear membrane is the biological membrane which surrounds the nucleus, encasing the genetic material. Furthermore, the cell membrane is made up of a single lipid bilayer structure while the nuclear membrane is made up of two lipid bilayer structures.

Cell membrane and nuclear membrane are two types of biological membranes present in eukaryotic cells. Their main function is to regulate the flow of materials through them.

Key Areas Covered

1. What is Cell Membrane
     – Definition, Structure, Importance
2. What is Nuclear Membrane
     – Definition, Structure, Importance
3. What are the Similarities Between Cell Membrane and Nuclear Membrane
     – Outline of Common Features
4. What is the Difference Between Cell Membrane and Nuclear Membrane
     – Comparison of Key Differences

Key Terms

Cell Division, Cell Membrane, Cytoplasm, Lipid Bilayer, Nuclear Envelope, Nuclear Membrane, Plasma Membrane

What is Cell Membrane

The cell membrane is the biological membrane which surrounds the cytoplasm of all types of cells. In eukaryotic cells, there are two types of cell membranes. They are the plasma membrane, which surrounds the cytoplasm, and internal membranes, which surrounds the matrix of different organelles including mitochondria, chloroplast, etc. Also, the cell membrane that surrounds the nucleus is known as the nuclear membrane. Additionally, some organelles such as endoplasmic reticulum and Golgi apparatus are completely membranous organelles. On the other hand, the other organelles such as lysosomes contain a fluid-filled matrix enclosed by the cell membrane.

Furthermore, the cell membrane is made up of a lipid bilayer with embedded proteins. Lipids including phospholipids, glycolipids, and sterols, glycolipids, and proteins including transmembrane proteins, lipid-anchored proteins, and peripheral proteins are the main biological molecules involved in the formation of the cell membrane. Moreover, the main function of the cell membrane is to physically separate the content of the cytoplasm from its extracellular environment. In addition, it serves as a selectively permeable membrane facilitating the transport of substances in and out of the cell.

What is Nuclear Membrane

The nuclear membrane is the biological membrane that surrounds the nucleus. Therefore, nuclear membrane only occurs in eukaryotic cells. The main feature of the nuclear membrane is the presence of two lipid bilayer structures in the membrane. We call these inner and outer membranes. The outer membrane is continuous with the endoplasmic reticulum while the inner nuclear membrane encloses the nucleoplasm. The space between the two lipid bilayers is known as the perinuclear space, which is about 20 to 40 nm wide.

Furthermore, the inner and outer nuclear membranes are connected by nuclear pores. Generally, nuclear pores are large protein complexes which are hollow. Their diameter is about 120 nm and the inner channel is about 40 nm in diameter. Moreover, the main function of the nuclear membrane is to regulate the passage of molecules responsible for all aspects of genome structure and function. In addition, it has a function during cell division. Generally, the nuclear envelope disappears during the prophase, releasing condensed chromosomes to the cytoplasm. It reforms after the formation of daughter nuclei during the anaphase.

Similarities Between Cell Membrane and Nuclear Membrane

• These are two types of biological membranes in a eukaryotic cell.
• They are made up of lipid bilayers.
• Furthermore, their main function is to enclose different structures of the cell regulating the passage of molecules through the membrane.
• Also, they act as semi-permeable membranes.

Difference Between Cell Membrane and Nuclear Membrane

Definition

Cell membrane refers to the semipermeable membrane surrounding the cytoplasm of a cell while nuclear membrane refers to a double membrane, enclosing a cell nucleus and having its outer part continuous with the endoplasmic reticulum. Thus, this is the main difference between cell membrane and nuclear membrane.

Also Known as

Moreover, the cell membrane is also known as the plasma membrane while the nuclear membrane is also known as the nuclear envelope.

Occurrence

Also, another difference between cell membrane and nuclear membrane is that the former occurs in both prokaryotes and eukaryotes while the latter only occurs in eukaryotes.

Enclosure

Moreover, while cell membrane encloses the cytoplasm of the cell, nuclear membrane encloses the nucleoplasm.

Number of Lipid Bilayers

Number of lipid bilayers is also a difference between cell membrane and nuclear membrane. Cell membrane comprises a single lipid bilayer structure while nuclear membrane comprises two lipid bilayer structures.

Persistence

Furthermore, cell membrane persists throughout the lifetime of a cell while the nuclear membrane disappears and reforms during the nuclear division.

Role

Their role is also an important difference between cell membrane and nuclear membrane. The former is responsible for regulating the flow of materials in and out of the cell while the latter is responsible for regulating the flow of materials in and out of the nucleus.

Conclusion

The cell membrane is the biological membrane which encloses the cytoplasm of the cell. It is made up of a lipid bilayer. The main function of the cell membrane is to regulate the flow of molecules in and out of the cell. On the other hand, the nuclear membrane is the biological membrane which encloses the nucleus. Moreover, it contains two lipid bilayer structures. While regulating the flow of materials in and out of the nucleus, the outer nuclear membrane is continuous with the endoplasmic reticulum. Therefore, the main difference between cell membrane and nuclear membrane is the lipid bilayer structure and function.

Reference:

1. Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. Cell Membranes. Available Here. 
2. Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. The Nuclear Envelope and Traffic between the Nucleus and Cytoplasm. Available Here. 

Image Courtesy:

1. “Cell membrane detailed diagram 4” By derivative work: Dhatfield (talk)Cell_membrane_detailed_diagram_3.svg (CC BY-SA 3.0) via Commons Wikimedia   
2. “Endomembrane system diagram en” By Mariana Ruiz LadyofHats (Public Domain) via Commons Wikimedia