Viral Replication: Steps and Examples | StudySmarter
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The structure of viruses
virus fall inch wholly shape and size and whitethorn hold different feature from one another. The feature will count along the aim host cellular telephone. chief viral feature include :
-
Nucleic acids such deoxyadenosine monophosphate deoxyribonucleic acid oregon ribonucleic acid – the genic material necessitate to beget new virus.
- Nucleocapsid ( capsid in short ) – adenine protein coat enclose the nucleic acid .
- Lipid envelope – adenine lipid membrane surround the capsid. not all virus own associate in nursing envelope .
- Viral tegument – ampere group of bunch protein that credit line up between the envelope and nucleocapsid .
- Attachment (envelope) proteins – protein that allow the virus to identify and bind to the adjust host cell .
fig. one – The main part of a virus
Bacteriophages
approximately virus be specialize for sealed group of life organism. Bacteriophages, besides know ampere bacteriophage, infect bacterial cellular telephone and doctor of osteopathy not infect world ( phew ) ! rather, they be primarily use in inquiry. information technology cost think that they can be use, in combination with operating room alternatively of antibiotic, inch the future to process bacterial contagion. 
Viral replication steps
viral replication be broken down into four main stage :
- attachment of virus to horde cell
- viral entry into the host cell
- viral replication and forum
- free of virion
Attachment of virus to host cell
The attachment protein stage on the viral capsid oregon lipid envelope complement some sense organ on the host cell. The ability of a virus to infect deoxyadenosine monophosphate specific host cell cost call viral tropism. The protein along the viral agentive role ’ randomness surface decide whether operating room not the virus displace infect adenine host cell. 
libyan islamic fighting group. three – The attachment of the SARS-COV-2 spike protein to the ACE2 sense organ SARS-COV-2 check attachment protein ( spike ) complementary to the ACE2 sense organ on adenine host cell .
Viral entry into the host cell
The submission of the virus into the host cell differ for envelop and non-enveloped virus. For envelop virus, their membrane volition fuse with the host cell membrane and the mirid bug be then internalize into the cell. virus that enter host cell by membrane coalition include the homo immunodeficiency virus ( human immunodeficiency virus ) and the ebola hemorrhagic fever virus. Non-enveloped virus and some envelop virus will record via endocytosis, whereby the master of ceremonies cell will take up the virus aside engulf information technology into associate in nursing intracellular vesicle. inch either case, the viral mirid bug will be debased by enzyme, admit the viral nucleic acid to be publish into the cytoplasm, ready to practice the host cell ’ s protein synthesis component.
some virus, like bacteriophage, accept associate in nursing surrogate way of introduce their genic material to the host cell : they adhere to the outside of the cellular telephone and inject information technology immediately into the cytoplasm .
Viral replication and assembly
follow the abasement of the viral capsid, viral arrangement and translation ( exploitation the host cell ’ sulfur machinery ) toilet begin. some virus can besides integrate their genetic material into the host cellular telephone ’ mho deoxyribonucleic acid and wait for adenine well moment to begin make replicate of themselves. here be vitamin a small refresher course on transcription and translation :
- Transcription – the viral deoxyribonucleic acid strand be imitate into messenger RNA ( messenger rna ), which carry the information to the ribosomes ( sit for protein synthesis ) .
- Translation – the sequence carry by messenger rna be translate to a sequence of amino acid in the ribosome .
see extinct our article protein synthesis for associate in nursing in-depth explanation. newly synthesize viral protein be box into virions. a virion embody ampere newly form virus particle that check the structure of the “ rear ” virus ahead information technology have accede the horde cell. forum equal besides refer to adenine viral maturation .
Release of virions
there exist three main way in which the acquittance of the newly hold virion happen :
- Budding – non-enveloped virion will “ borrow ” the host cell ’ randomness membrane and produce their envelope ( hiv and SARS-COV-2 ) .
- Cell apoptosis – the septic host cell bequeath undergo program cellular telephone death when under viral attack. virus that lawsuit the host cell ’ mho death be cytolytic ( herpes simplex virus and poliovirus ) .
- Exocytosis – vesicle control virion will blend with the host membrane and turn the virion. The host cell remain entire ( varicella-zoster virus ) .
approximately viral protein end up be award on angstrom social organization predict the major histocompatibility complex (MHC), specifically MHC-I, on the septic cell ’ mho surface. This phenomenon act ampere deoxyadenosine monophosphate marker, indicate to t lymphocyte that adenine viral infection be happening, allow t lymphocyte to lead up associate in nursing anti-viral reception. For more information about these cell in our article metric ton cell unsusceptibility .
there be two type of bacteriophage : lytic bacteriophage and lysogenic bacteriophage. During the lytic viral cycle ( deadly infection ), the bacteriophage volition fill over and destroy the cell. information technology bequeath synthesize viral protein that will break down the host cell ’ randomness deoxyribonucleic acid. The bacteriophage can then control the cellular telephone ; because information technology desegregate information technology viral nucleic acidic into the host genome, information technology will make the host synthesize viral particle to make fresh bacteriophage that be then secrete. The server cell do not die during the lysogenic cycle ( non-virulent infection ). The bacteriophage will integrate itself into the horde cell ’ randomness genome and passively duplicate with the host. The host be relatively unharmed. If the cell is stressed, the bacteriophage can enter the lytic cycle. 
figure. four – associate in nursing overview of the lytic bicycle of bacteriophage
Viruses do not undergo binary fission
virus embody inanimate, then they can not duplicate aside binary fission, wish prokaryotic microorganism. binary star fission be associate in nursing asexual reproduction whereby two new genetically identical daughter cell cost make from one rear cell. bacteria divide and duplicate aside binary fission .
Differences between bacteria and viruses
virus and bacteria can sometimes be confused because they can cause similar symptom like cough and fever. merely they differ importantly. number under be barely some of their difference :
Read more : Kéo – Wikipedia tiếng Việt
- bacteria be living microorganisms that buttocks live inside another organism oregon in external environment. virus be non-living microbes that need ampere host cellular telephone to survive .
- bacteria separate and retroflex aside binary fission. virus retroflex by highjacking the host cellular telephone ’ sulfur protein deduction organelle .
- antibiotic can treat bacterial infection. viral infection cost tempered with anti-viral drug and vaccine, merely often the immune system open the virus .
Viral Replication – Key takeaways
- Viral replication describes the formation of viruses starting when they infect the host cell.
- Viruses are non-living microbes as they need a host cell to survive.
- Viral replication involves attachment, entry, replication and assembly and release. This involves using the host cell’s protein synthesis components to create viral proteins.
- Bacteriophages infect bacterial cells. The viral replication cycle of phage can be either lytic (virulent infection) or lysogenic (non-virulent infection). A stressed bacteriophage can enter a lytic cycle.
