Acellular Meaning - Types & Functions

There is a life which exists on the Earth which is supported by various living and non living things. When we talk about which thing this living and the non living things are made up of. So the answer is non living things are made up of the fundamental unit of matter which is the “atom”. The atom was first explained by John Dalton. Since, the living things are made up of cells or they are also referred to as the cellular organisms which can be divided into various cells. But the term which is used to describe a single unit of cell which exists in a single unit is known as the acellular organisms.

Acellular also refers to the substances which are not considered as completely living or cells like the viruses and various vaccines.

Some Examples of Acellular Organisms :

Viroids are small, circular, single-stranded RNA molecules that lack a protein coat. They infect plants and cause diseases such as potato spindle tuber disease and citrus exocortis. Viroids replicate by using host cell machinery to make copies of themselves, but do not encode for any proteins.

Prions are abnormal, infectious proteins that cause a variety of neurodegenerative diseases in animals, such as scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle, and Creutzfeldt-Jakob disease (CJD) in humans. Prions are able to induce conformational changes in normal cellular proteins, leading to the accumulation of abnormal aggregates in the brain and eventually causing cell death.

Viroids and prions are called acellular because they do not have a cell membrane or any other cellular structures. Viroids are simply small, circular RNA molecules that lack a protein coat, and prions are abnormal, infectious proteins. They both rely on the host cell's machinery to replicate and cause disease. They are not considered as a living organisms because they lack the fundamental cellular structures, metabolic pathways and genetic material (DNA/RNA) required for independent life. In contrast, cellular organisms, such as bacteria and viruses, have a cell membrane and other cellular structures, and are able to carry out all the processes necessary for life on their own.

Image : Viroids virus (self made)

Image : prions (self made)

Cell Definition

When we say that the thing is living or not? The answer to the question is the activity the thing performs and it is able to respire and perform the various metabolic activities needed. All the basic things that take place in a living body are performed in the fundamental unit of the living system known as the ‘Cell’. Cell was first discovered by Robert Hook.

Cell is the place where all the metabolic and chemical reactions take place. The food we eat or the air we breathe all of these functions are performed by the cell. The cell has cell organelles which have specific function. Like plasma membrane allows the entry and exit of food and waste.

Cells produce some compounds that are also known as acellular components.

Cellular and Acellular

Cellular organisms are the organisms which are living and have the characteristics of a cell and it can have minimum one cell also it can be thousands of cells. Cellular organisms may vary from a single cell amoeba to a combination of lakhs of cells in a peel of skin of a human.

Acellular things are the substances that are not enough complete to say that they are made up of cells. For example, viruses are acellular because they are not viable in the environment and they are made up of only protein and the genetic material. Also the organic compounds produced by the cells are referred to as the acellular like the lactic acid produced by the LAB (Lactic Acid Bacteria) from lactose in the milk is also an acellular substance as it is produced by the living cell by performing the metabolic reaction.

Unicellular and Multicellular

As we know, the protist is called the Euglena which exists in freshwater bodies as a single cell. The microorganisms which exist as single cells in the environment and perform their activities. It is not necessary that only protists come under this category; there are a large number of bacteria that come under these categories like Halophiles and Bacillus species of the Monera kingdom. All these microorganisms are known as the unicellular microorganisms.

When we talk about humans they are the most advanced living beings present on this planet. So, now try to make the concept clear that all living things are made up of cells, now the cells in a group perform certain functions to form a tissue, also certain tissues combine to form organs and the organs work in coordination to form an organ system. Each and every part of the human body is made up of cells dead or living, so the cells are present in more than one in number so they are known as multicellular organisms.