We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Does "Acellular" Mean?

By Meg Higa
Updated Mar 05, 2024
Our promise to you
AllThingsNature is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At AllThingsNature, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

The Latin prefix a- means “without.” The Latin word cellula means “a small room.” Acellular is a term most recognized in the biological sciences to mean living things without conventional cell structures and functions.

Plant cells were first observed through a microscope in 1665. By 1840, the Cell Theory had established the atomistic principle that the cell is the basic unit of life, the smallest living biological organism. The metabolic functions of a cell — respiration, growth, reproduction — were adopted as the requisite definition of life itself. The egg is the quintessential model of a cell, an ostrich egg being the largest known specimen of a single cell.

Human beings are differentiated multicellular organisms with approximately 100 trillion co-dependent, but individual, cells. Difficult as it is to fathom, by a very large margin, the majority of the Earth's total biomass is unicellular life — organisms such as bacteria consisting of just one cell. By the turn of the 21st century, advances in technology and microbiology had discovered acellular organisms such as viruses without one or more of the defining characteristics of a cell.

As with the ostrich egg, one traditionally indispensable key characteristic of a cell is its enclosure, its shell, the cell membrane. A single complex cell was assumed to have the capacity for life because all of the many functional ingredients necessary were self-contained and accessible. The unicellular protozoa called ciliates furthermore have tiny, vibrating hair-like growths projecting off their cell membranes and enabling them to move. This motility, interpreted as purposeful, represented the deterministic principle of life. The most common substitute meaning of acellular is apparent life not enclosed by a cell membrane.

Most scientists, certainly virologists, have come to believe that viruses are alive, despite being mostly just strands of their particular genetic material sheathed in a protective coat of specific proteins that help them identify and infect other host cells. They had been originally thought to be, in a sense, inert, with their sometimes harmful effects merely the metabolic changes of their living host organisms. In 2003, a class of unusually large viruses called mimivirus was discovered to be capable of creating proteins on their own, without need of a host. This led to the speculative assumption that there might be many other viruses with abilities that had once been reserved for cellular life.

An acellular entity is, by definition, smaller than a cell. Such organisms are difficult to find, much less study, without the help of imaging equipment such as electron microscopes. Nevertheless, science continues to discover not only new viruses, but also other unique acellular entities, such as prions and fosmids, that might be candidates for the moniker “living organism.” An entirely separate classification name for them, Acytota, was proposed. Whether acellular organisms truly constitute life, the long-standing Cell Theory as well as the accepted definitions of life are under scientific challenges.

Frequently Asked Questions

What does the term "acellular" refer to in biology?

"Acellular" in biology describes structures or entities that are not made up of cells. This can include substances like viruses, which consist of genetic material encased in a protein coat, and do not have the cellular machinery necessary for independent life processes that characterize cellular organisms.

How do acellular organisms like viruses reproduce if they are not made of cells?

Viruses, which are acellular, cannot reproduce on their own. Instead, they must infect a host cell and hijack its machinery to replicate their genetic material and produce new virus particles. This process often results in damage or destruction of the host cell.

Are there any medical applications for acellular materials?

Acellular materials have significant medical applications, particularly in tissue engineering and regenerative medicine. Acellular dermal matrices, for example, are used in wound healing and reconstructive surgery to promote tissue regeneration without the risk of immune rejection, as they lack cellular components that can trigger an immune response.

Can acellular components trigger an immune response?

While acellular components generally have a lower risk of provoking an immune response due to the absence of cellular antigens, some acellular substances, like vaccines that contain inactivated viruses or bacterial toxins, are designed to elicit an immune response to confer immunity without causing disease.

What is the difference between acellular and multicellular organisms?

Acellular organisms lack cells entirely, while multicellular organisms are composed of multiple, specialized cells that work together. Multicellular life forms, such as humans, plants, and animals, have complex structures and systems that arise from the organization and interaction of various cell types.

Do acellular entities have any role in ecosystems or the environment?

Acellular entities like viruses play crucial roles in ecosystems by influencing population dynamics and genetic diversity. They can control the population of certain species, thereby maintaining ecological balance, and can also drive evolution through horizontal gene transfer, introducing new genetic material into organisms.

AllThingsNature is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

AllThingsNature, in your inbox

Our latest articles, guides, and more, delivered daily.

AllThingsNature, in your inbox

Our latest articles, guides, and more, delivered daily.