Difference WikiBiology

Difference Between Membranous Organelles and Nonmembranous Organelles

Main Difference

The main difference between Membranous Organelles and Nonmembranous Organelles is that Membranous Organelles are generally enclosed by single or double membranes that are structurally similar to the plasma membrane, whereas any membrane does not enclose any Nonmembranous Organelles.

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Membranous Organelles vs. Nonmembranous Organelles

Membranous organelles are those organelles which normally bounded by a single or double plasma membrane to separate the organelles’ fluid-filled spaces; on the other hand, nonmembranous organelles are those organelles which do not consist of any bounded plasma membrane for separating the organelles from the cell cytoplasm. All prokaryotes do not consist of any membranous organelles, while all prokaryotic organelles are nonmembranous organelles.

The membranous organelles consist of fluid-filled cavities inside the organelle; on the other hand, all nonmembranous organelles do not consist of any fluid-filled cavities inside the organelles. A definite boundary is given to the organelles, which are membranous organelles; on the flip side, the nonmembranous organelles are incessant with the cytoplasm.

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The membranous organelles are only present in eukaryotic cells; on the contrary, the nonmembranous organelles are present in both prokaryotic and eukaryotic cells. Various examples of membranous organelles are endoplasmic reticulum, mitochondria, nucleus, Golgi apparatus, Golgi complex, Golgi vesicles, secretory vesicles, plastids, peroxisomes, phagosomes, pinocytotic vesicles, and lysosomes; on the other hand, the nonmembranous organelles listed as nucleoid, ribosomes, proteasomes, cilia, flagella, centrioles, and some components of the cytoplasm such asmMicrofilaments, microtubules, and intermediate filaments.

Comparison Chart

Membranous OrganellesNonmembranous Organelles
The membranous organelles are considered as one of the two types of organelles of the cell, which are surrounded by a unit membraneThe second type of organelles are nonmembranous organelles in which cell organelles do not consist of a membrane that encloses them
Function
To separate the organelles’ fluid-filled spacesDo not consist of any bounded plasma membrane for separating the organelles from the cell cytoplasm
In Prokaryotes
Prokaryotes do not consist of any membranous organellesThe prokaryotic organelles are nonmembranous
Fluid-Filled Organelles
Consist of fluid-filled cavities inside the organelleDo not consist of any fluid-filled cavities inside the organelles
Definite Boundary
A definite boundary is given to the membranous organellesThe nonmembranous organelles are incessant with the cytoplasm
Presence
Only present in eukaryotic cellsPresent in both prokaryotic and eukaryotic cells
Enclosed by a Membrane
Organelles surrounded by a single membrane and a double membraneAny unit membrane does not enclose the organelles
Examples
Various examples are endoplasmic reticulum, mitochondria, nucleus, Golgi apparatus, Golgi complex, Golgi vesicles, secretory vesicles, plastids, peroxisomes, phagosomes, pinocytotic vesicles, and lysosomesSome examples are nucleoid, ribosomes, proteasomes, cilia, flagella, centrioles, and some components of the cytoplasm such as microfilaments, microtubules, and intermediate filaments
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What are Membranous Organelles?

The organelles which consist of a plasma membrane all around them are known as membranous organelles. Some organelles like endoplasmic reticulum, Golgi apparatus, nucleus, mitochondria, lysosomes, and plastids are considered as membranous organelles.

The membranous organelles are said to be fluid-filled and are generally separated from the contents of the cytoplasm through the defined membrane. The organelle ‘Endoplasmic Reticulum’ is referred to as a double membrane-bounded structure, which considered to be involved in the transferring of substances from one part of the organelle to the other part of the cell.

Endoplasmic Reticulum has two types, depending on the presence of the ribosomes: SER and RER. SER does not contain ribosomes on its surface, while RER contains ribosomes on its surface and involve in the production of proteins. ‘Golgi Apparatus’ is another known single membranous organelle that consists of a secretory function in the cell.

‘Lysosomes’ are also membranous organelles that formed from the Golgi apparatus. Lysosomes consist of digestive enzymes. ‘Mitochondria’ is known as the powerhouse of the cell, which is also a membrane-bounded organelle involved in cellular respiration. Mitochondria is present in different shapes such as spherical, rod-shaped, or oval.

‘Chloroplasts’ are the double membranous organelles that consist of both smooth membranes. It also consists of a matrix called stroma, the complex layers of disk-like structures, which are known as thylakoids. The green color of the leaves is because of the presence of the chloroplast, which consists of a green chlorophyll pigment inside the leaf.

What are Nonmembranous Organelles?

The organelles which do not consist of any definite boundary are known as nonmembranous organelles. Furthermore, these nonmembranous organelles do not consist of any fluid-filled cavities. The organelles which are present in prokaryotes are said to be nonmembranous.

Organelles like centrioles, nucleoid, ribosomes, flagella, cilia, and parts of the cytoplasm such as microfilaments, intermediate filaments, and microtubules are nonmembranous organelles. ‘Nucleoid’ is a nonmembranous organelle and is considered a region of cytoplasm where the genetic material of prokaryotes is present.

‘Ribosomes’ are also nonmembranous organelles and are responsible for the synthesis of proteins from mRNA (messenger RNA). Ribosomes are made of RNA with bound proteins. Two types of ribosomes are the 70S and 80S. Prokaryotes contain 70S ribosomes, and 80S is present in eukaryotes.

The ‘Cytoskeleton’ is also known as nonmembranous organelle and which functions in providing the support and shape to the cell. It has two types of nonmembranous components; Microfilaments and Microtubules. Microfilaments are known to be unbranched hard rod-like structures, which are protein fibers and made up of a tubulin protein, Microtubules, which are hollow and have a cylindrical structure. They are tubes of protein that made up of tubulin protein.

‘Centrioles’ are considered as nonmembranous organelles which are made up of triplets of microtubules, usually arranged around a cavity, but there is no central microtubule. Therefore, they show the microtubules in an arrangement of 9+0.

Key Differences

  1. The organelles which are enclosed by a cell membrane to distinguish them from the fluid-filled spaces of the cytoplasm are known as the membranous organelles; on the other hand, the organelles are not bounded by any cell membrane which separates them from the outer cellular environment are known as nonmembranous organelles.
  2. Prokaryotes usually lack membranous organelles; however, prokaryotes are considered as nonmembranous organelles.
  3. The organelles which are membranous consist of fluid-filled cavities inside them, while the organelles of the cell, which are nonmembranous, do not consist of any fluid-filled cavities inside them.
  4. The membranous organelles consist of a defined boundary around them; on the contrary, the nonmembranous organelles do not consist of any defined boundary; rather, they are continuous with the cytoplasm of the cell.
  5. The cells of eukaryotes consist of membranous bound organelles, whereas both prokaryotes and eukaryotes contain nonmembranous organelles.
  6. Endoplasmic reticulum, mitochondria, nucleus, Golgi apparatus, Golgi complex, Golgi vesicles, secretory vesicles, plastids, peroxisomes, phagosomes, pinocytotic vesicles, and lysosomes are known examples of membranous organelles; on the flip side, nucleoid, ribosomes, proteasomes, cilia, flagella, centrioles, and some parts of the cytoplasm such as microfilaments, microtubules, and intermediate filaments are the nonmembranous organelles.

Conclusion

The above discussion concludes that the membranous organelles are surrounded by single or double membranes, which gives them a definite shape and structure and separates them from the outer cellular cavities, while the nonmembranous organelles do no consist of any membrane rather they are continuous with the contents in the cytoplasm.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White