In this article, we will discuss the characteristics of viruses and the structure and role of viruses in life. The word "virus" certainly does not feel strange to us.
How not? We must often or have heard of diseases caused by viruses either through mass media or at school. Viruses are intermediate beings between living things and microscopic non-living things.
Viruses are known as parasites obligate intracellular at living things because they cannot live without being inside the body of a living creature (host) where it will infect its host and then reproduce itself. For further explanation about viruses, let's look at the explanation below.
Characteristics of Viruses
Here are the characteristics of the virus you need to know:
Viruses can only live in the body of other living things as parasites obligate intrasellules. He will infect the body of the living creature that he lives in and then multiply inside.
Viruses are acellular (not cells) which means they do not have cell organelles to carry out their own metabolism or reproduction such as cell membranes, ribosomes, cytoplasm or other organelles. Viruses also do not have metabolic enzymes, but some viruses have enzymes for the process of replication and transcription by combining with host cell enzymes such as the Herpes virus.
3. Microscopic size
Viruses are very small (microscopic) organisms where they only reach 20-300 millimicrons (1 micron = 1000 millimicrons). The smallest virus has a diameter of 20 nm with a number of genes 4.
Meanwhile, the largest viruses have a diameter of 80 nm (such as the Ebola virus ) with a number of genes that are hundreds. Even the most large viruses cannot be observed through a light microscope but with an electron microscope.[1945electronmicroscope” width=”250″ height=”305″/>
4. Can only infect certain types of hosts
Not all viruses can infect all living things. Every virus that exists can only infect certain types of hosts such as the rabies virus infect mammals, swine flu attacks pigs, birds and humans.
This occurs because the type of host that can be infected by a virus or commonly referred to as the "host range" is determined based on the evolution of recognition of the virus using the suitability of "lock and key" between proteins on the outside of the virus with specific receptor (recipient) molecules on the surface of the host cell.
5. Viruses with DNA or RNA[1945CharacteristicsofVirusesandTheirRoles” width=”450″ height=”353″/>
There are DNA viruses and RNA viruses, naming them based on nucleic acids that make up genomes such as DNA or RNA. So, viral capsid is only composed of one type of nucleic acid, only DNA or RNA.
6. Can be crystallized
Viruses are the only creatures that can be crystallized. This is the reason why the virus is classified as a transitional creature (being between living things and non-living things) because it can be crystallized even the simplest cells cannot be crystallized. Viruses are still classified as living things because they still have nucleic acids such as DNA or RNA.
7. Has a capsid
Viruses have proteins that are used as a protective layer to protect the genetic material of a virus called a capsid. There are various forms of capsid based on the type of virus such as round (spherical), polyhedral, helical, or more complex forms. Capsids have protein chains called capomers.
8. Cannot divide themselves
Viruses cannot divide themselves but reproduce themselves by utilizing living cells as their host.
9. Diverse genomes
Viral genomes are proteins that are used to load genetic material or to recycle their lives. Genomes in viruses are more diverse than conventional genomes (single-helical single-strand DNA) found in other living things.
The viral genome forms depend on the type of virus such as double-stranded DNA, double-stranded RNA, single-stranded DNA or single-stranded RNA. Viral reproduction occurs through rearrangement using materials present in the viral genome nucleic acid.
10. Cannot metabolize itself
Viruses only consist of a sheath of proteins and nucleic acids and do not have cell membranes, cytoplasm, and other organelles such as ribosomes, mitochondria, golgi bodies, and others.
This is what causes the virus not to do own metabolism. Because in metabolism requires enzymes to carry out biochemical processes in the body.
To be able to carry out metabolism, the virus uses enzymes and metabolic substances from cells that host it because the virus cannot produce its own energy and synthesizes enzyme proteins.
Below is an explanation of the structure of the virus that you need to know.
1. Head of the virus
Inside the head of the virus there are nucleic acids (DNA or RNA) which are covered by the capsid. Capsid is a protein envelope consisting of one unit of protein, namely capsomer. Capsid is used as a nucleic acid protector from damage and various environmental conditions, giving shape to viruses, providing enzyme proteins so that the virus is able to penetrate the host cell membrane when it will infect.
2. Viral neck
The neck is the link between the head and tail of the virus. Not all types of viruses have a neck, only complex viruses have a neck. The function of the neck of this virus is to support the head of the virus.
3. Virus tail
The tail of the virus is shaped like a tube equipped with tail fibers. The tail of the virus consists of 2 parts, namely the sheath and tail fibers. Tail fibers are fibers at the end of the tail that function as recipients of stimuli (receptors). Meanwhile, the tail sheath is used to infect and destroy the cell layer of the cell so that it can enter RNA / DNA into these cells to reproduce.
The Role of Viruses in Life
Viruses are beneficial and some are harmful in life. The following is below the role of viruses in life both beneficial and detrimental to living things.
A. Favorable virus
We naturally hear how viruses can harm living beings but we rarely hear how viruses can benefit living things. Well, in this section, we will learn to understand how viruses can be useful in life. The following is the explanation below.
1. As a Vaccine
Vaccines are antigenic materials made from weakened pathogens (bacteria, viruses or toxins) that are used to produce immunity to a disease. Pathogens are microorganisms that can cause disease in their hosts such as bacteria, viruses or toxins.
Pathogens that have been weakened are certainly not harmful to humans or other living things. By giving a vaccine to the human body, antibodies to pathogens that invade the body will be produced. That is, the vaccine becomes a protector of the attack of the pathogen. Here are some examples of vaccines.
- OPV (Oral Polio Vaccine) – vaccines for polio pain
- MMR ( Measles, Mumps, Rubella ) – vaccines for chickenpox , mumps, German measles
- HBV  (Hepatitis B Vaccine) – vaccine for jaundice
- HZV (Varicella Zoster Vaccine) – vaccine for chickenpox
2 . Weakening Bacteria
DNA from lysogenic viruses can enter and damage the DNA of pathogenic bacteria (parasitic bacteria that cause disease in living things). This is certainly very beneficial because the virus can be used to weaken the bacteria that enter the body and make it harmless.
3. Supporting Medical Sciences
Viruses can be used in making chromosome maps in the medical world so as to help medical experts analyze and make new breakthroughs in the field of medicine.
4. As Anti-toxin
The incorporation of viral DNA with other DNA such as human DNA that can control the production of anti-toxins, would certainly be very beneficial. Why? Because when a virus whose DNA has been combined with human DNA, it is connected to bacterial DNA to produce bacteria that contain human anti-toxin. These bacteria will divide themselves and produce other bacteria that have anti-toxins in their bodies.
B. Harmful virus
Viruses include microorganisms that can cause disease in hosts such as humans, animals and plants (pathogens). The types of diseases caused by viruses include:
Viruses that Harm Humans
 Harmful virus ” width=”600″ height=”285″/>
Influenza better known as "flu" is an infectious disease caused by influenza virus (the RNA virus from the Orthomyxoviridae family) that attacks birds and mammals such as humans. Usually, the symptoms experienced by sufferers are fever, chills, muscle aches, cough, runny nose, headache, and fatigue.
2. Hepatitis [1945-1945]
Hepatitis, commonly known as jaundice, is inflammation of the liver due to toxins such as chemicals / drugs or pathogens. Usually, hepatitis is caused by viruses such as hepatitis A virus (cause of hepatitis A), hepatitis B virus (cause of hepatitis B), hepatitis C virus (cause of hepatitis C), hepatitis D virus (cause of hepatitis D), and hepatitis E virus (cause of hepatitis E).
This disease causes the sufferer's eyes and skin to turn yellow. This is because the virus makes the liver swell so that bile flows and circulates to all parts of the body.
Rabies is a deadly virus originating from saliva or the bite of an infected animal that attacks parts of the brain and nervous system. Animals that can be infected by this virus are warm-blooded animals such as dogs, bats, cats, apes, and others. The symptoms of this virus are fever, headache, excess saliva, muscle spasms, paralysis, and mental confusion.
4. Ebola 
Ebola virus can cause severe bleeding, organ failure, and even death. This virus is found in mainland Africa precisely in the Zaire area (Ebola river). Spread occurs through skin contact and body fluids of the sufferer. The initial symptoms of this virus are fever, headache, muscle aches, and chills. In fact, at a later stage, the sufferer can experience internal bleeding resulting in vomiting or coughing up blood.
Besides the four types of diseases above, the virus also causes measles, polio, swollen eyes, mumps, dengue fever, herpes simplex, AIDS, bird flu , swine flu, SARS, and chickenpox.
1. Nail and Mouth Disease (Foot and Mouth Disease)
Nail and mouth viruses attack buffalo, cattle, or other livestock resulting in they are unable to walk or eat (paralysis).
2. Tetelo Disease
Tetelo disease (Chicken Sampar) usually attacks chickens and causes acute diarrhea in chickens so the chicken will weaken, cough, diarrhea, lose balance and die. This disease is caused by a virus New Castle Disease 
3. Rabies [1945-1914]
This disease is caused by the rabies virus [r900d7rus] which attacks warm-blooded animals such as dogs, cats, bats, apes, and others.
4. Poultry Tumors / Cancer
[RousSarcomaVirus(RSV) can cause tumors or cancers in chickens and other poultry.
Harmful Viruses Plants
1. [Mosaic 9007]
Mosaic virus attacks plants such as tobacco, tomatoes and pumpkins, causing patches of fruit or the leaves. Examples of this type of virus are:
-  Cucumber Mosaic Virus, the cause of damage to cucumber fruit.
- Tobacco Mosaic Virus (TMV), the cause of yellow spots on tobacco leaves.  The Wheat Mosaic Virus, the cause of damage to wheat.
- Bean Mosaic Virus, the cause of damage to beans.
-  Sugarcane Mosaic Virus, the cause of damage on sugar cane.
- Turnip the Yellow Mosaic Virus, the cause of damage to cotton leaves so that the leaves roll up.
2. Citrus Vetn Phloem Degeneration
Citrus Vetn Phloem Degeneration was the cause of the death of citrus plants where the pathogens were transmitted through insect vectors
Well, hopefully the discussion of the characteristics of viruses, the structure and role of viruses in life as explained above is useful. Thank you!
"If you're doing your best, you don't have any time to worry about failure." H. Jackson Brown, Jr.