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A Venture into Viruses



Due to the COVID-19 pandemic, scientists had to revisit their prior knowledge and conduct studies and experiments to be able to discover new aspects of the coronavirus. This resulted in spreading accurate information to answer the public’s pressing concerns and formulating effective treatment strategies aimed to boost the world’s resistance to the virus and decrease mortality rates.


For this article, we will be tackling some questions about viruses, more specifically the different types, viral structure, and life cycle. This will provide you with a crash course about the topic and help prepare you for this portion of the MCAT.



1. What are the components of a virus?


Although a virus has genetic material in the form of DNA or RNA, it does not have a nucleus. It has a protein coat or envelope called capsid which serves as protection for the viral genome. Some viruses may have an envelope external to the capsid which is composed of glycoprotein and phospholipids. The envelope contains proteins that aid in the adherence and binding of the viral particles to the host cell. These viruses do not survive external to the environment of the host and are weak against heat and some cleaning properties which makes it easier to eradicate such.


2. How are viruses classified by shape?


First, helical viruses have a structure that resembles an elongated tube or hollow cylinder as well as capsomers that surround the genome in a spiral arrangement. Second, icosahedral viruses are spherical with twenty triangular sides. Third, complex viruses do not adhere to the aforementioned shapes; rather, these have irregular and abnormal shapes as well as other additional structures.


3. What are the five steps that are involved in allowing the virus to spread in an organism?


  1. Attachment: Through the spike protein, the virus binds to the receptor protein located on the surface of the host cell.

  2. Entry or Penetration: The genetic material of the virus passes through the cell membrane and into the cell.

  3. Genome Replication and Gene Expression: There is the creation of a copy of the viral genome which would be utilized in the expression and translation to produce viral proteins.

  4. Assembly: New viral particles are formed and assembled. The RNA and protein combine to create a capsid.

  5. Release: There is the exit of completed viral particles to contaminate other cells.


4. What is a bacteriophage? What are the two types of life cycles for bacteriophages?


A bacteriophage is a kind of virus that only infects and affects bacteria. It has a head that stores genetic material, a tail that allows the genetic material to enter the host bacteria, and tail fibers that help in the attachment of the bacteriophage to the host cell.


The first type is the lytic cycle which pertains to the fast and continuous genome replication in a host bacterium until this reaches its maximum capacity, bursts, and releases the viral particles to the environment.


The second type is the lysogenic cycle in which the viral genetic material is integrated into the bacteria’s genome. It results in a prophage or a provirus. This prophage only replicates the viral DNA and does not translate such into proteins.


5. What are subviral particles?


The first subviral particle is the prion which forms when a protein is folded in an abnormal manner and shape. This is infectious because it influences other normally-folded proteins to become the same way also. What makes the prion so dangerous is that it disrupts cell functioning and processes, resulting in a variety of serious illnesses including Bovine Spongiform Encephalopathy (Mad Cow Disease), Chronic Wasting Disease, and Gerstmann-Straussler-Scheinker Syndrome.


The second subviral particle is the viroid which is composed of single-stranded, circular RNA and lacks a protective protein coating. This is capable of interrupting the translation process and is found to only affect plants.



I hope that these questions can guide you in your MCAT preparation processes! Remember that studying viruses serves as the foundation for your future endeavors as a member of the medical community because you need to understand how a virus enters a cell and subsequently infects other cells. Through such, you may be able to plot the patterns and take part in groundbreaking projects that battle against such viral infections and discover treatments/cures to existing related concerns.



Thank you for reading!

Oriana Tolentino



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