Main Difference – Cell Membrane vs Plasma Membrane
Cell membrane and plasma membrane are two terms which are used interchangeably to describe different boundaries of the cell. The main difference between cell membrane and plasma membrane is that cell membrane is the boundary of the cell whereas plasma membrane can be the boundary of a cell or an organelle. Both cell membrane and plasma membrane are selectively permeable to molecules. In animal cells, the cell membrane is the outermost layer which separates the cellular contents from the external environment. Plant, fungal, and bacterial cells consist of a cell wall, surrounding the cell membrane.
Key Areas Covered
1. What is Cell Membrane
– Definition, Composition, Function
2. What is Plasma Membrane
– Definition, Composition, Function
3. What are the Similarities Between Cell Membrane and Plasma Membrane
– Outline of Common Features
4. What is the Difference Between Cell Membrane and Plasma Membrane
– Comparison of Common Features
Key Terms: Cell, Cell Membrane, Cytoplasm, Lipids, Organelles, Phospholipid Bilayer, Plasma Membrane, Proteins
What is Cell Membrane
Cell membrane is a semipermeable membrane which surrounds the cytoplasm of the cell. It provides support and helps to maintain the shape of the cell. The main function of the cell membrane is to maintain the integrity of the cell interior. Cell membrane allows only selected molecules to pass through it.
Figure 1: Cell Membrane
The cell membrane is mainly composed of lipids and proteins. Lipids give flexibility to the membrane while proteins serve as transporters and receptors. Phospholipids are the major lipid component of the cell membrane. They form a lipid bilayer where hydrophilic parts of the lipid molecules are arranged towards the cytosolic and extracellular parts of the cell. The hydrophobic parts are arranged inside the bilayer, forming the hydrophobic core. Due to the amphipathic nature (containing both hydrophilic and hydrophobic parts in the bilayer) of the lipid bilayer, only small, hydrophobic molecules are allowed to pass through the cell membrane. Other large hydrophilic molecules and ions are transported by proteins in the cell membrane. Integral proteins and peripheral proteins are the two protein components of the cell membrane.
What is Plasma Membrane
Plasma membrane refers to a semipermeable barrier which surrounds cellular compartments. The plasma membrane which surrounds the cell is called the cell membrane. Plasma membrane also surrounds the organelles of eukaryotes. Typically, an organelle is a dynamic structure which performs a certain function inside the cell. Therefore, in order to perform their functions, the interior of the organelle should be a defined environment. The intracellular spaces of different organelles may also differ from each other. The maintenance of the homeostasis of the extracellular spaces inside the organelles is the function of the plasma membrane. Based on the function of the organelle, the structure of the plasma membrane that surrounds the organelle is also changed. Mitochondrial membrane is shown in figure 2.
Figure 2: Mitochondrial Membrane
Some plasma membranes are specialized to perform functions of the organelles. For example, mitochondrium is the organelle that performs cellular respiration in eukaryotes. Thereby, the mitochondrial membrane is specialized to perform electron transport chain. Chloroplast membrane is also specialized to perform photosynthesis. The plant cell vacuoles are also enclosed by the plasma membrane.
Similarities Between Cell Membrane and Plasma Membrane
- Both cell membrane and plasma membrane are two types of boundaries in the cell.
- Both cell membrane and plasma membrane are made up of a phospholipid bilayer.
- Both cell membrane and plasma membrane are selectively permeable to molecules.
- Both cell membrane and plasma membrane create a specific environment inside the compartment, independently from the external environment.
- Both cell membrane and plasma membrane allow cellular communication.
- Both cell membrane and plasma membrane may contain enzymes.
Difference Between Cell Membrane and Plasma Membrane
Definition
Cell Membrane: Cell membrane is a semipermeable membrane that surrounds the cytoplasm of the cell.
Plasma Membrane: Plasma membrane is a semipermeable barrier that surrounds the cellular compartments.
Correspondence
Cell Membrane: Cell membrane encloses the entire cell.
Plasma Membrane: Plasma membrane encloses cells or organelles.
Composition
Cell Membrane: Cell membrane is made up of a phospholipid bilayer with embedded proteins.
Plasma Membrane: The composition of the plasma membrane may change based on the requirements of the cellular compartment, which is enclosed by the plasma membrane.
Conclusion
Cell membrane and plasma membrane are two types of boundaries which surround the cell and cellular compartments. Both types of membranes are made of a phospholipid bilayer. Cell membrane surrounds the cell while plasma membrane surrounds the cellular compartments. The structure of the plasma membrane may change based on the requirements of the type of cellular compartment. The main difference between cell membrane and plasma membrane is the type of compartments surrounded by each type of membrane.
Reference:
1. Bailey, Regina. “Function, Structure, and Composition of the Cell Membrane.” ThoughtCo, Available here.
2. Cooper, Geoffrey M. “Structure of the Plasma Membrane.” The Cell: A Molecular Approach. 2nd edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
Image Courtesy:
1. “Cell membrane detailed diagram 4” – derivative work: Dhatfield Cell_membrane_detailed_diagram_3.svg: *derivative work: Dhatfield (talk)Cell_membrane_detailed_diagram.svg: LadyofHats Mariana Ruiz – Cell_membrane_detailed_diagram_3.svg, (CC BY-SA 3.0) via Commons Wikimedia
2. “2508 The Electron Transport Chain” By OpenStax College – Anatomy & Physiology, Connexions Web site. , Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
Leave a Reply