BIOL 100 Smith

Biology 100 Angelina Smith

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Viruses living or not?

What is life?

Definition: the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death. ("Life", Oxford English Dictionary, 2023)

Life is...

1. Made up of one or more cells.2. Chemical reactions called metabolism. 3. Internal regulation or homeostasis. 4. Regulated growth. 5. Asexual or sexual reproduction. 6. Response to stimuli. 7. Adaptation and evolution. (What Is Life? (Article) | Intro to Biology, n.d.)

Properties of life ...

Viruses have been historically categorized as non-living because they are not made up of cells, they are incapable of homeostasis, they are not capable of growth, development, nor energy processing. (Khan Academy, n.d.)

Why historically have viruses been categorized as non-living?

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Why is the controversy surrounding viruses still not completely resolved?

There has been some argument that viruses are infact microorganisms and that it is possible that they even evolved away from celled organisms to become the simple organism they are today. Also, no living organism can survive completely independently which is one of the arguments that viruses are not alive. So there is room to argue that viruses are in fact alive. (Society, n.d.)

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What are viruses?

Viruses are...

Tiny acellular parasite
Vary in size, shape, method of replication, and host
Carry RNA or DNA within a protective capsid
Depend on a specialized host cell to replicate
Unknown evolution and origin
Usually damage or destroy host cell during replication
Can infect hosts vertically (offspring) and horizontally (host to host)
Infection symptoms vary from chronic to intermittent to asymptomatic
Some have the ability to cause cancer (Clark et al., 2018)

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How does the structure of a virus differ from the structure of Prokaryotes?

In a way viruses and prokaryotes are structured similarly. Prokaryotes are larger and are a single-celled organism, they have a cell wall. Whereas, viruses are enveloped in a protein coat and some have a lipid membrane called an envelope. Prokaryote DNA is located in cell cytoplasm. In a virus DNA/RNA is located within a capsid. Prokaryotes have their own ribosomes whereas viruses must hijack host ribosomes to reproduce their genetic material. (Fowler et al., 2013)

The argument that viruses are living stems from the fact that it is believed that viruses evolved from a single-celled organism. However, they have evolved to the point where they no longer meet the criteria to be classified as a living thing. The fact that they are incapable of homeostasis, they cannot reproduce without hijacking their hosts ribosomes, and they cannot survive outside a host all lends to the argument that viruses are not living. (Society, n.d.)

How does this information provide evidence for or against the argument that viruses should be classified as living?

How does a cell get energy?

Cells rely on outside substances to convert into energy. Humans need food and plants need sun and water. Most cellular energy is derived from sugars, proteins, and fats. Cells get energy through a process called cellular respiration which, through an oxidation process, breaks down glucose in order to produce ATP which is capable of being used throughout the body. The molecules are put through an oxidation process that breaks them into smaller energy rich molecules that can be used throughout the cell. (Tarantino, 2023)

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The fact that viruses are not capable of creating their own energy or even really utilizing energy bolsters the argument that viruses are not living. Viruses hijack the host cell forcing the cell to make copies of the viruses genetic material. The virus never actually uses energy itself.

How does a virus get energy? How does this affect the argument whether viruses are living or not?

Most viruses do not necessarily need energy, they force the host cell to utilize its own energy stores in the production of new viral genetic material. The virus takes over the cell and all of its processes. (Elitsa, 2023)

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(ScienceFacts, 2020)

Prokaryotes, however, reproduce through an a-sexual process called binary fission. The process occurs fairly quickly, first the genetic material is copied, the cell doubles in size, the cell develops a septum in the middle where the split will occur resulting in two daughter cells that can each individually repeat the process over and over again.

How does a cell reproduce?

Eukaryotic cells have several phases within which its existence, division, and reproduction occur. During the Interphase the cell grows, rests, and synthesizes or replicates both strands of the DNA helix in preparation for division. Next the cell enters a second growth phase where the organelles are also duplicated and the microtubules in the mitotic spindle begin pulling the separated chromosomes apart into two complete cells.

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Does this information argue for or against viruses being classified as living? Because viruses are unable to replicate outside the use of a host cell's processes I believe that it argues against a virus being classified as living.

How does a virus reproduce?

Viruses cannot replicate on their own. They all need a host cell to reproduce, however their method of reproduction varies, but they all follow a similar process. Using very specialized proteins a virus will attach itself to a host cell, during attachment the virus is able to enter the cell by merging their capsid with the cell membrane. Once inside the capsid coating degrades and allows for the release of viral genetic code and the virus begins to replicate its genetic material. Next the pieces are assembled where the proteins and genomes are synthesized into new virions. Finally comes the release of the newly assembled virions. This happens in two different ways, they can bud from the cell without causing the death of the cell or through lysis where the cell bursts to release the virions. (Louten, 2016)

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How and why does a cell mutate?

The most common cause of cell mutation is disfunction during meiosis, when the chromosomes within a cell is splitting in half. Nondisjunction is when chromosomes split abnormally which results in too many or not enough chromosomes. A person with the correct number of chromosomes is an euploid, too many is trisomy, and not enough chromosomes is an aneuploid. Whereas chromosome inversion occurs when bits of information detach and rearange incorrectly, it is unknow what exactly causes this. ( Fowler et al., 2013)

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While, the mutation of viruses and the mutation of cells is quite similar in nature there are still some fairly vast differences. Sometimes the virus must mutate to survive while the cell mutation is unintentional. The virus can mutate itself into extinction as a cell can mutate in a way that it can no longer support life. Does this similarity argue that the virus is alive? I think viral mutation is the closest thing to life the virus experiences and very well could go into the virus is alive argument.

How and why does a virus mutate?

Viruses mutate for the same reason cells do, a virus must reproduce to survive, and mutation occurs during reproduction. Viruses multiply quickly and that leaves a lot of room for error during the process. Viruses also mutate easily if two or more viruses infect the same host at the same time. A virus will often mutate as the host becomes immune to the virus. (Best, n.d.) Viruses can mutate quickly or slowly. Antigenic drift is a slow process of viral antigen mutation. Antigenic shift is when a virus rapid. (CDC, 2021)

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Why are some people resistant/naturally immune to diseases and viruses?

Due to their genes, some people are naturally more immune to some pathogens. During Covid it was discovered that some people, even when exposed, were naturally resistant and never got sick. Scientists at the University of Sheffield, UK found that over 1300 different genes play a part in our immunity. This information is not particularly new though as scientists have known for years that about 1 in 100 people of European descent are naturally immune to HIV. (Wilson, 2023)

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Using the language live and dead in relation to virus material within vaccines gives strength to the argument that viruses should be classified as living, however I believe inert is a more appropriate term.

How do vaccines provide immunity?

Vaccines help the body to provide immunity to viruses by causing the body's immune system to produce antibodies to a known pathogen. Vaccines use antigens, or substances that are known to cause immune responses. Examples are dead or weakened pathogens, pieces of their genetic material, or bacterial toxin made innert. While vaccines are known to be effective and safe vaccines often need to be administered over time to remain effective. Live-attenuated vaccines are known to provide much longer and stronger immunity compared to non-live vaccines. (CDC, 2023)

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What is the purpose of DNA/RNA in a cell?

DNA is a double-strand helix whose structure allows for it to make a copy of itself during cell division. It carries all of the genetic material within a cell and plays a vital role in each organism. Within that genetic material are the instructions for an organism to function. (Minchin & Lodge, 2019) While DNA carries the genetic material, the role of RNA is to carry the information to ribosomes to be translated into proteins the cell can use. (Wang & Farhana, 2023)

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How does this affect my opinion on viruses categorized as living? If replication of and consisting of genetic material was a factor this information would argue for classifying viruses as living. The fact that viruses contain genetic material alone gives credence to it being classified as living.

What is the purpose for DNA/RNA in a virus?

DNA and RNA have very similar roles in viruses as they do in cells. Some viruses carry RNA, some DNA, DNA carrying viruses can be single strand or double helix. Because viruses do not have ribosomes to transmit their genetic material, they rely on polymerases. These polymerases are specific to DNA or RNA and are responsible for copying the material to produce a daughter strand. (Choi, 2011)

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Are viruses subject to evolution?

Viruses actually evolve rapidly and often, this allows for them to adapt and survive ever changing environments. We have seen this in our lifetime watching the genetic mutation of Covid in real time. Like other species, virus mutations create genetic diversity. Since viruses have particularly high mutation rates it means there is considerable genetic diversity. Creating the opportunity for vaccine and drug resistance. Because viruses are so diverse there is opportunity to survive. (Stern & Andino, 2016) To survive a virus must evolve, to evolve a virus must be replicating within a host cell. While undergoing such rapid replication errors are bound to result. These errors can either be beneficial or the end of that virus. These mutations are what allow viruses to evade immune systems and even jump species. (Holmes, 2020) Viral evolution does argue heavily for viruses to be classified as living, however, a virus can only mutate while replicating within a host cell. Without the host the virus remains inert. In a way viral evolution is dependent upon the host and it's response to the virus, or multiple viruses infecting the same host as opposed to the virus itself.

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Bacteria vs. Virus

Bacteria are a single celled prokaryote and viruses lack organelles and cytoplasm. The majority of bacteri have some for of a cell wall whereas viruses do not. The majority of bacteria are also much larger than viruses, however, there have been monster viruses found. Bacteria do not need a host to exist or reproduce whereas viruses can only exist outside a host for a short time and can only reproduce within a host. Bacteria reproduce asexually through binary fission and viruses must insert their genetic code into a host genome to make copies of itself. Bacteria have riboosomes and viruses do not. Bacteria have DNA/RNA located in the cytoplasm and viruses contain DNA/RNA within a capsid. Bacteria generally cause localized infections whereas viruses cause systemic infections. Bacterial infections can be treated with antibiotics while viral infections cannot. (The University of Queensland, 2020) Comparing an organism of similar characteristic to viruses makes clear how different viruses are from living organisms. While the infections may be difficult to distinguish at first glance, there are clear differences upon investigation. Viruses do mirror life, but that is the extent.

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Reflection

The best argument, for viruses are alive, I have seen so far is that if a virus can be killed, then clearly it is inherently alive. (Koonin & Starokadomskyy, 2016) However most antivirals work by stopping a virus from reproducing not actually by killing it like antibiotics do to bacteria. Hand sanitizer breaks down the outer capsid of the virus leaving it inert, what we would call dead to simplify the process. (Does Hand Sanitizer Kill Viruses? What Else Is It Effective Against? | Steroplast Healthcare, n.d.) The argument of what defines life will vary from person to person and some aspects will hold more weight for one person than another. I think science is the ability and process of constantly questioning information and investigation without end. I don't think we should try to end the argument, but be open to all possibilities through research. Maybe just agree to disagree for now.

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Resources

CDC. (2021, September 21). How Flu Viruses Can Change. Centers for Disease Control and Prevention.https://www.cdc.gov/flu/about/viruses/change.htm#:~:text=Another%20type%20of%20change%20is
CDC. (2023, May 24). Understanding How Vaccines Work. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/hcp/conversations/understanding-vacc-work.html
Choi, K. H. (2011). Viral Polymerases. Viral Molecular Machines, 267–304. https://doi.org/10.1007/978-1-4614-0980-9_12

Clark, M. A., Douglas, M., & Choi, J. (2018). Biology 2e. OpenStax.
Does Hand Sanitizer Kill Viruses? What Else is it Effective Against? | Steroplast Healthcare. (n.d.). Www.steroplast.co.uk. https://www.steroplast.co.uk/knowledge-base/does-hand-sanitizer-kill-viruses.html#question-four

Elitsa. (2023, October 16). How do viruses trick their hosts into feeding them? Science Journal for Kids and Teens. https://www.sciencejournalforkids.org/articles/how-do-viruses-trick-their-hosts-into-feeding-them/#:~:text=All%20organisms%20need%20energy%2C%20but

Fowler, S., Roush, R., & Wise, J. (2013, April 25). Introduction - Concepts of Biology - OpenStax. Openstax.org. https://openstax.org/books/concepts-biology/pages/1-introduction
Holmes, B. (2020, July 17). How Viruses Evolve. Smithsonian Magazine. https://www.smithsonianmag.com/science-nature/how-viruses-evolve-180975343/

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Khan Academy. (n.d.). Are viruses dead or alive? (article) | Cells. Khan Academy. https://www.khanacademy.org/test-prep/mcat/cells/viruses/a/are-viruses-dead-or-alive#:~:text=Most%20biologists%20say%20no.
Koonin, E. V., & Starokadomskyy, P. (2016). Are viruses alive? The replicator paradigm sheds decisive light on an old but misguided question. Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences, 59(59), 125–134. https://doi.org/10.1016/j.shpsc.2016.02.016

Louten, J. (2016). Virus Replication. Essential Human Virology, 1(1), 49–70. https://doi.org/10.1016/B978-0-12-800947-5.00004-1
Minchin, S., & Lodge, J. (2019). Understanding biochemistry: structure and function of nucleic acids. Essays in Biochemistry, 63(4), 433–456. https://doi.org/10.1042/EBC20180038
Oxford Dictionary. (2023). Oxford Languages. Oxford Languages; Oxford University Press. https://languages.oup.com/google-dictionary-en/

ScienceFacts. (2020, July 13). Binary Fission: Definition with Examples & Diagram. Science Facts. https://www.sciencefacts.net/binary-fission.html
Society, M. (n.d.). Are viruses alive? Microbiologysociety.org. https://microbiologysociety.org/publication/past-issues/what-is-life/article/are-viruses-alive-what-is-life.html#:~:text=The%20authors%20concluded%20that%20viruses
Stern, A., & Andino, R. (2016). Viral Evolution. Viral Pathogenesis, 233–240. https://doi.org/10.1016/B978-0-12-800964-2.00017-3

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Tarantino, C. (2023). Cellular Respiration: What Is It, Its Purpose, and More | Osmosis. Www.osmosis.org. https://www.osmosis.org/answers/cellular-respiration#:~:text=Cellular%20respiration%20is%20a%20series
The University of Queensland. (2020, April 20). What’s the difference between bacteria and viruses? Imb.uq.edu.au; The University of Queensland. https://imb.uq.edu.au/article/2020/04/difference-between-bacteria-and-viruses

Wang, D., & Farhana, A. (2023, July 29). Biochemistry, RNA Structure. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK558999/#:~:text=The%20primary%20function%20of%20RNA
What is life? (article) | Intro to biology. (n.d.). Khan Academy. https://www.khanacademy.org/science/biology/intro-to-biology/what-is-biology/a/what-is-life
Wilson, C. (2023). DO SOME PEOPLE HAVE NATURALLY STRONGER IMMUNE SYSTEMS? New Scientist, 257(3424), 40–41. https://doi.org/10.1016/s0262-4079(23)00215-4

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Biology 100 Angelina Smith

Viruses living or not?

What is life?

Life is...

Properties of life ...

Viruses have been historically categorized as non-living because they are not made up of cells, they are incapable of homeostasis, they are not capable of growth, development, nor energy processing. (Khan Academy, n.d.)

Why historically have viruses been categorized as non-living?

Why is the controversy surrounding viruses still not completely resolved?

What are viruses?

Viruses are...

How does the structure of a virus differ from the structure of Prokaryotes?

How does this information provide evidence for or against the argument that viruses should be classified as living?

How does a cell get energy?

How does a virus get energy? How does this affect the argument whether viruses are living or not?

How does a cell reproduce?

How does a virus reproduce?

How and why does a cell mutate?

How and why does a virus mutate?

Why are some people resistant/naturally immune to diseases and viruses?

How do vaccines provide immunity?

What is the purpose of DNA/RNA in a cell?

What is the purpose for DNA/RNA in a virus?

Are viruses subject to evolution?

Bacteria vs. Virus

Reflection

Resources

Do you have an idea?

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Got an idea?

Let the communication flow!

Do you have an idea?

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Do you have an idea?

Do you have an idea?

Got an idea?

Let the communication flow!

Do you have an idea?

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Do you have an idea?