what is viruses in biology

What is biological virus and what are its characteristics?

Biological Viruses. Everybody knows the term “virus” and it is often associated with a computer virus. A biological virus is a microscopic infectious agent.First viruses are not life forms.They are not ‘alive’ but they possess some significant characteristic that differentiates them from inert matter as well.

Which is the largest and smallest virus in biology?

The smallest viruses are only 25–30 nm in diameter, while the largest (e.g. mimivirus, an infectious agent of amebae) are 400 nm or more in size. Which is the world's smallest cell? Mycoplasma gallicepticum, a parasitic bacterium which lives in the primate bladder, waste disposal organs, genital, and respiratory tracts, is thought to be the ...

What are the three categories of viruses?

The 3 Most Common Types of PC Virus Infections

• Trojans. RECOMMENDED VIDEOS FOR YOU... ...
• Botnets. The web is also where you risk contracting a drive-by bot infection that will enlist your computer as an agent in a fraudster's arsenal.
• Scareware. Fake antivirus programs, which are often referred to as "scareware," is the third and arguably most irritating leg of the malware stool.

What two things does every virus have?

Viruses generally come in two forms: rods or spheres. However, bacteriophages (viruses that infect bacteria) have a unique shape, with a geometric head and filamentous tail fibers. No matter the shape, all viruses consist of genetic material ( DNA or RNA) and have an outer protein shell, known as a capsid.

What is a simple definition of viruses?

Listen to pronunciation. (VY-rus) In medicine, a very simple microorganism that infects cells and may cause disease. Because viruses can multiply only inside infected cells, they are not considered to be alive.

What is virus in biology class 11?

The viruses are the non- cellular organisms and a small infectious agent that are characterized by having an inert crystalline structure. When they enter the living cell they take over the machinery of the host cell and start replicating themselves and killing the host.

Who discovered virus?

Beijerinck, in 1898, was the first to call 'virus', the incitant of the tobacco mosaic. He showed that the incitant was able to migrate in an agar gel, therefore being an infectious soluble agent, or a 'contagium vivum fluidum' and definitively not a 'contagium fixum' as would be a bacteria.

What are the functions of virus?

The main purpose of a virus is to deliver its genome into the host cell to allow its expression (transcription and translation) by the host cell. A fully assembled infectious virus is called a virion.

What is structure of virus Class 11?

Viruses are mere strands of DNA or RNA surrounded by a protective protein coat called a capsid. They are living, only, when they have invaded some living cell. Outside of a host cell, viruses are completely inert.

What is virus in biology PDF?

Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat. Viruses may be viewed as mobile genetic elements, most probably of cellular origin and characterized by a long co-evolution of virus and host.

What is virus Byjus?

A virus is a small infectious agent reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal. Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.

Are viruses living or non living class 11?

non-livingViruses are considered as something between living and non-living because they do not grow or reproduce by themselves. This makes them non-living.

What is the function of a virus?

The main task of the virus is to carry its DNA or RNA genome to the host cell, which then can be transcribed by the host cell. The viral genome is packed in a capsulated symmetric protein.

What is the genetic material of a virus?

The virus, having RNA as its genetic material. There are two different types of RNA virus

Why can't a virus replicate?

For instance, a virus cannot replicate itself outside the host cell. This is because viruses lack the required cellular machinery. Therefore, it enters and attaches itself to a specific host cell, injects its genetic material, reproduces by using the host genetic material and finally the host cell splits open, releasing the new viruses.

Why can't viruses be found in any kingdom?

These microbes belong to the family viridae and genus virus. Viruses could not be placed in any of the kingdoms because they are practically neither living nor dead. The term virus was coined by the Dutch microbiologist, Martinus Willem Beijerinck in the year 1897. It is derived from Latin, which means poison or venomous substance.

What is the most commonly used classification system for studying the system of virus classification?

The Baltimore classification is the most commonly used for studying the system of virus classification. This system was developed by an American biologist David Baltimore in the 1970s, for which he was awarded the Nobel Prize. The below flowchart describes the classification of viruses based on their different criteria.

How small are viruses?

Viruses are composed of a core of DNA or RNA surrounded by a protein coat. They are very small and their size ranges from 20 nanometers to 250 nanometers. Therefore, they can only be seen with an electron microscope.

What is the name of the virus that infects bacterial cells?

The virus which infects bacterial cells is known as bacteriophage . There are many varieties of bacteriophages, such as DNA virus, MV-11, RNA virus, λ page, etc.

How do viruses infect living organisms?

Viruses are microscopic biological agents that invade living hosts and infect their bodies by reproducing within their cell tissue.

Why are viruses important?

Because some viruses incorporate their DNA into host DNA, they can be genetically modified to carry genes that would benefit the host.

How does the lysogenic cycle work?

Like the lytic cycle, in the lysogenic cycle the virus attaches to the host cell and injects its DNA. From there, the viral DNA gets incorporated into the host’s DNA and the host’s cells. Each time the host’s cells go through replication , the virus’s DNA gets replicated as well, spreading its genetic information throughout the host without having to lyse the infected cells.

How do viruses replicate?

There are two processes used by viruses to replicate: the lytic cycle and lysogenic cycle. Some viruses reproduce using both methods, while others only use the lytic cycle. In the lytic cycle, the virus attaches to the host cell and injects its DNA.

What is a virus that is outside of a host cell called?

A virus that is outside of a host cell is known as a virion. Not only are viruses microscopic, they are smaller than many other microbes, such as bacteria. Most viruses are only 20–400 nanometers in diameter, whereas human egg cells, for example, are about 120 micrometers in diameter, and the E. coli bacteria has a diameter of around 1 micrometer.

What is the definition of parasite?

organism that is home to a parasite. infection. Noun. disease caused by microscopic organisms, such as bacteria. influenza. Noun. contagious disease, characterized by fever, exhaustion, and difficulty breathing.

What is RNA in biology?

ribonucleic acid (RNA) Noun. chemical compound that plays a variety of roles within cells; each molecule of RNA is made up of a string of building blocks that usually are abbreviated as A, C, G and U. virion. Noun. a complete virus with an RNA or DNA core and protein coat existing outside of a host cell. virus.

What is the biological nature of viruses?

Ivanovsky and in 1898 by the Dutch scientist Martinus W. Beijerinck. Beijerinck first surmised that the virus under study was a new kind of infectious agent, which he designated contagium vivum fluidum, meaning that it was a live, reproducing organism that differed from other organisms. Both of these investigators found that a disease of tobacco plants could be transmitted by an agent, later called tobacco mosaic virus, passing through a minute filter that would not allow the passage of bacteria. This virus and those subsequently isolated would not grow on an artificial medium and were not visible under the light microscope. In independent studies in 1915 by the British investigator Frederick W. Twort and in 1917 by the French Canadian scientist Félix H. d’Hérelle, lesions in cultures of bacteria were discovered and attributed to an agent called bacteriophage (“eater of bacteria”), now known to be viruses that specifically infect bacteria.

What is a virus made of?

A virus particle is made up of genetic material housed inside a protein shell, or capsid. The genetic material, or genome, of a virus may consist of single-stranded or double-stranded DNA or RNA and may be linear or circular in form.

Why can't viruses synthesize proteins?

Unlike true organisms, viruses cannot synthesize proteins, because they lack ribosomes (cell organelles) for the translation of viral messenger RNA (mRNA; a complementary copy of the nucleic acid of the nucleus that associates with ribosomes and directs protein synthesis) into proteins .

How do viruses use their energy?

Viruses must use the ribosomes of their host cells to translate viral mRNA into viral proteins. Viruses are also energy parasites; unlike cells, they cannot generate or store energy in the form of adenosine triphosphate (ATP). The virus derives energy, as well as all other metabolic functions, from the host cell.

Why are viruses dangerous?

Why are some viruses dangerous? When some disease-causing viruses enter host cells, they start making new copies of themselves very quickly, often outpacing the immune system’s production of protective antibodies. Rapid virus production can result in cell death and spread of the virus to nearby cells.

What are the two types of shapes that viruses have?

Shapes of viruses are predominantly of two kinds: rods (or filaments), so called because of the linear array of the nucleic acid and the protein subunits, and spheres, which are actually 20-sided (icosahedral) polygons.

How are viruses transmitted?

Virtually all plant viruses are transmitted by insects or other organisms (vectors) that feed on plants. The hosts of animal viruses vary from protozoans (single-celled animal organisms) to humans. Many viruses infect either invertebrate animals or vertebrates, and some infect both. Certain viruses that cause serious diseases of animals and humans are carried by arthropods. These vector-borne viruses multiply in both the invertebrate vector and the vertebrate host.

What are the components of a virus?

What's interesting about viruses is that they have two or three components. Starting from the inside, you will have a nucleic acid, which can be either RNA or DNA, and in both cases the nucleic acid can be either single-stranded or double-stranded. Then surrounding the nucleic acid will be a protein coat that's in the form of capsid, or little small units that are assembled in a certain way. That is what all viruses have. Now, some viruses will also have an envelope which they obtain as they emerge from the cell. Viruses are very interesting in that they can only survive inside a living cell. So they must have a living cell in order to survive and replicate. Antibiotics are not effective against viruses, but vaccines are, as well as some antivirals.

How do viruses work?

Viruses must infect cells and use components of the host cell to make copies of themselves. Often, they kill the host cell in the process, and cause damage to the host organism. Viruses have been found everywhere on Earth. Researchers estimate that viruses outnumber bacteria by 10 to 1. Because viruses don’t have the same components as bacteria, they cannot be killed by antibiotics; only antiviral medications or vaccines can eliminate or reduce the severity of viral diseases, including AIDS, COVID-19, measles and smallpox.

How many viruses outnumber bacteria?

Researchers estimate that viruses outnumber bacteria by 10 to 1. Because viruses don’t have the same components as bacteria, they cannot be killed by antibiotics; only antiviral medications or vaccines can eliminate or reduce the severity of viral diseases, including AIDS, COVID-19, measles and smallpox.

Do viruses have an envelope?

Now, some viruses will also have an envelope which they obtain as they emerge from the cell. Viruses are very interesting in that they can only survive inside a living cell. So they must have a living cell in order to survive and replicate.

How are viruses classified?

The 400 known viruses are classified in several ways: by genome core (RNA or DNA), host (animals, plants, or bacteria), method of reproduction (such as retrovirus), mode of transmission (such as enterovirus), and disease produced (such as hepatitis virus). Treatment.

What is a defective virus?

defective virusone that cannot be completely replicated or cannot form a protein coat; in some cases replication can proceed if missing gene functions are supplied by other viruses; see also helper virus.

What is the term for the time between a virus and a host?

This carrier state can take any of several different forms. The term latencyis used to denote the interval from infection to clinical manifestations. In the lentiviruses, it was formerly mistakenly believed that virus was inactive during this period. The true situation is that lentivirusesare rapidly replicating and spawning dozens of quasi-species until a particularly effective one overruns the ability of the host's immune systemto defeat it. Other viruses, however, such as the herpesviruses, actually enter a time known as “viral latency,” when little or no replication is taking place until further replication is initiated by a specific trigger. For many years all forms of latency were thought to be identical, but now it has been discovered that there are different types with basic and important distinctions.

How big are viruses?

They range in size from 15 to several hundred nanometers. Classification of viruses depends on physiochemical characteristics of virions as well as on mode of transmission, host range, symptomatology, and other factors. For viruses not listed below, see the specific name. Synonym(s): filtrable virus. 3.

How are viruses replicated?

Within the host cell the genetic material of a DNA virus is replicated and transcribed into messenger RNA by host cell enzymes, and proteins coded for by viral genes are synthesized by host cell ribosomes. These are the proteins that form the capsid(protein coat); there may also be a few enzymes or regulatory proteins involved in assembling the capsid around newly synthesized viral nucleic acid, in controlling the biochemical mechanisms of the host cell, and in lysing the host cell when new virions have been assembled. Some of these may already have been present within the initial virus, and others may be coded for by the viral genome for production within the host cell.

What is the role of lymphocytes in viral latency?

In viral latency, most of the host cells may be protected from infection by immune mechanisms involving antibodies to the viral particles or interferon. Cell-mediated immunity is essential, especially in dealing with infected host cells. Cytotoxic lymphocytesmay also act as antigen-presenting cellsto better coordinate the immune response. Containment of virus in mucosal tissues is far more complex, involving follicular dendritic cells and Langerhans cells.

Which virus primarily affects the liver?

hepatotropic virusa virus that primarily affects the liver, such as the hepatitis viruses.

What is a virus made of?

A virus is made up of a DNA or RNA genome inside a protein shell called a capsid. Some viruses have an external membrane envelope.

What is the genetic material of a virus?

All viruses have genetic material (a genome) made of nucleic acid. You, like all other cell-based life, use DNA as your genetic material. Viruses, on the other hand, may use either RNA or DNA, both of which are types of nucleic acid.

What is a viral infection?

In everyday life, we tend to think of a viral infection as the nasty collection of symptoms we get when catch a virus, such as the flu or the chicken pox. But what's actually happening in your body when you have a virus?

How does a virus enter a cell?

Entry. Virus enters cell by endocytosis. In the cytoplasm, the capsid comes apart, releasing the RNA genome.

How do viruses reproduce?

Viruses reproduce by infecting their host cells and reprogramming them to become virus-making "factories."

How are viruses and bacteria different?

Even though they can both make us sick, bacteria and viruses are very different at the biological level. Bacteria are small and single-celled, but they are living organisms that do not depend on a host cell to reproduce. Because of these differences, bacterial and viral infections are treated very differently. For instance, antibiotics are only helpful against bacteria, not viruses.

What is the protein shell of a virus?

The capsid, or protein shell, of a virus is made up of many protein molecules (not just one big, hollow one). The proteins join to make units called capsomers, which together make up the capsid. Capsid proteins are always encoded by the virus genome, meaning that it’s the virus (not the host cell) that provides instructions for making them.

What is the term for viruses that have a layer or envelope of lipids?

Wrapping . Viruses that have a layer or envelope of lipids , which they obtain from the cell membrane of their host cells, and that is used to inject the genetic material into the cell.

How long have viruses been around?

In any case they are very primitive organisms, with an enormous capacity of mutation that allows them to adapt and change constantly, and of which there is no fossil record: the known virus species date back no more than 90 years .

What is the name of the virus that causes skin lesions?

Herpes simplex virus (HSV) . An extremely common human virus that generates skin lesions (known as herpes) and of which there are two variants: one genital and another that prefers the tongue, mouth, eyes and pharynx.

What is the RNA virus that attacks tobacco plants?

Tobacco mosaic virus . It is an RNA virus that attacks plants (it was discovered in the tobacco plant) and produces whitish or yellowish spots on its leaves. It was the first virus discovered.

Why are viral diseases recurrent?

In some cases, the outer part of their bodies has specialized proteins in the disguise, which allow them to change their chemical appearance and not be recognized by the cells of the immune system . That is why viral diseases are recurrent and do not have more treatment, except for certain retroviral drugs, such as those used to fight AIDS.

Is papilloma a virus?

Human Papilloma Virus . It is a family of extremely common viruses in man, some sexually transmitted (HPV) and others by touch, which usually cause warts and are mildly harmless, except for certain strains that have been linked to cancer.

Can viruses survive on their own?

Viruses can infect different life forms: animals, plants, bacteria and even other viruses (so-called virophages ), since they cannot survive on their own. There are in almost all existing ecosystems , they are the most abundant biological form on the planet: more than 5 thousand species have been known since the discovery of their existence in 1899, and it is believed that there could be millions of species.

How does a virus reproduce?

A virus has a shell that contains it's RNA, and reproduces by hi-jacking a normal cell's mechanisms. A prion is a protein, with no shell, that catalyzes (encourages) other proteins to fold the same way as the prion, without using RNA or a cell's reproductive mechanisms. 3 comments.

Who said viruses are with you?

Posted 9 years ago. Direct link to Leah Joy Savage's post “So, viruses are with you ...”

Is a virus alive?

Though viruses are not considered "dead" per se, they are similarly not considered alive. Of the eight characteristics of life (cells, homeostasis, adapt, respond, reproduce, grow, energy, grow), viruses only meet one: reproduction. This is not enough for scientists to consider them "alive.".

Do white blood cells attack viruses?

In a way, yes. White blood cells and other good body substances are specially made to attack the viruses. The attacked cells become weaker, but white blood cells prevent further attack.

Can a mutation cause a protein to be identical to a virus?

I think it is rather unlikely that a spontaneous mutation would just so happen to produce a protein that would be identical to a protein produced by a virus. That would be just too specific.

Is RNA ambisense or negative?

RNA viruses can be further classified according to the sense or polarity of their RNA into negative-sense and positive-sense, or ambisense RNA viruses. Positive-sense viral RNA is similar to mRNA and thus can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA-dependent RNA polymerase before translation.

Recommended Video

Bacteriophage and HIV

• These microbes belong to the family viridae and genus virus. Viruses could not be placed in any of the kingdoms because they are practically neither living nor dead. The term virus was coined by the Dutch microbiologist, Martinus Willem Beijerinck in the year 1897. It is derived from Latin, which means poison or venomous substance. Once a susceptib...

See more on byjus.com

Classification Based on The Presence of Nucleic Acid

Classification Based on The Structure Or Symmetry

Classification Based on The Replication Properties and Site of Replication

Classification Based on The Mode of Transmission