Difference between membranous organelles and nonmembranous organelles

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 either membrane does not enclose any nonmembranous organelles …

Membranous versus nonmembranous organelles

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

Membranous organelles consist of fluid-filled cavities within the organelle; on the other hand, all nonmembranous organelles do not consist of fluid-filled cavities within the organelles. A defined limit is given to the organelles, which are membranous organelles; on the other hand, nonmembranous organelles are incessant with the cytoplasm.

Membranous organelles are only present in eukaryotic cells; on the contrary, nonmembranous organelles are present in both prokaryotic and eukaryotic cells. Several 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, nonmembranous organelles are listed as nucleoids, ribosomes, proteasomes, cilia, flagella, centrioles, and some components of the cytoplasm, such as microfilaments, microtubules, and intermediate filaments.

Comparative chart

Organelles consisting of a surrounding plasma membrane are known as membranous organelles. Some organelles such as the endoplasmic reticulum, Golgi apparatus, nucleus, mitochondria, lysosomes, and plastids are considered membranous organelles.

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

The endoplasmic reticulum has two types, depending on the presence of ribosomes: SER and RER. SER does not contain ribosomes on its surface, while RER contains ribosomes on its surface and participates in the production of proteins. The ‘Golgi apparatus’ is another known unique membranous organelle consisting of a secretory function in the cell.

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

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

Organelles that do not have a defined boundary are known as nonmembranous organelles. Furthermore, these nonmembranous organelles do not consist of fluid-filled cavities. The organelles that are present in prokaryotes are said to be non-membranous.

Organelles such as centrioles, nucleoids, 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 the cytoplasm where the genetic material of prokaryotes is present.

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

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

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

Key differences

1. Organelles that are enclosed by a cell membrane to distinguish them from fluid-filled spaces in the cytoplasm are known as membranous organelles; on the other hand, organelles are not delimited by any cell membrane that separates them from the external cellular environment, they are known as nonmembranous organelles.
2. Prokaryotes generally lack membranous organelles; however, prokaryotes are considered nonmembranous organelles.
3. Membranous organelles consist of fluid-filled cavities inside, while cell organelles, which are not membranous, do not have fluid-filled cavities inside.
4. The membranous organelles consist of a defined boundary around them; on the contrary, the nonmembranous organelles do not have any definite boundary; rather, they are continuous with the cytoplasm of the cell.
5. The cells of eukaryotes consist of membrane-bound organelles, whereas both prokaryotes and eukaryotes contain nonmembranous organelles.
6. The 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 other hand, nucleoids, ribosomes, proteasomes, cilia, flagella, centrioles and some parts of the cytoplasm, such as microfilaments, microtubules and intermediate filaments, are the nonmembranous organelles.

The above discussion concludes that the membranous organelles are surrounded by single or double membranes, which gives them a defined shape and structure and separates them from the outer cell cavities, while the nonmembranous organelles do not consist of any membrane, but are continuous. with the content. in the cytoplasm.