Viruses are the smallest known infectious agents and lack cellular organization. They contain either DNA or RNA, but not both, and are obligate intracellular parasites that depend on host cell machinery for replication. Viruses infect host cells through attachment to receptors and are then uncoated inside the cell. They hijack the host cell to synthesize viral components and assemble new viral particles that are then released to infect other cells.
Classifications of Fungi
Characteristics of all Fungi
Structure of Fungi
Reproduction
Classification of Fungi
Basidiomycota
sexual reproduction occur by basidium , will be present spore is called basidiospore .
Asexual by budding ,fragementation, conidiospores.
Ascomycota
microscopic sexual structure in which nonmotile spores, called ascospores.
Mostly the ascomycota is sexual but some asexual it lacks the ascospore.
Zygomycota
Two spore
mitospores ( or) sporangiospore
chlamitospore (or) zygospore
Deuteromycota
Imperfect Fungi referring to our "imperfect" knowledge of their complete life cycles.
sexual life cycle that is either unknown or absent.
Asexual reproduction is by means of conidia or may be lacking.
culture media
SDA medium – sabouraud dextrose agar
Viral classification and Types of Replication in virus Rakshith K, DVM
Precise presentation on Viral classification and Types of replication in Virus.
Entry of virus
Spread of virus
General steps in a virus replication cycle
Attachment, Penetration, Uncoating, Multiplication
Multiplication of Single-Stranded RNA (ss RNA) Viruses
Multiplication of Double-Stranded RNA (ds RNA) Viruses
Multiplication of Single-Stranded DNA (ss DNA) Viruses
Multiplication of Double-Stranded DNA (ds DNA) Viruses
Release of new virions
Common viral diseases of Bovines
When fresh liquid medium is inoculated with a given number of bacteria and incubated for sufficient period of time, it gives a characteristic growth pattern of bacteria.
If the bacterial population is measured periodically and log of number of viable bacteria is plotted in a graph against time, it gives a characteristic growth curve which is known as growth curve or growth cycle.
Viruses that infect bacteria.
Occur widely in nature in close association with bacteria.
Readily isolated from faeces, sewage and other natural sources.
Tadpole shaped, with hexagonal head and a cylindrical tail.
Head consists of a tightly packed core of ds DNA surrounded by a protein coat or capsid.
The tail composed of a contractile sheath surrounding the hollow core
Terminal base plate having prongs or tail fibres attached.
Obligate intracellular, unable to self-replicate.
Once inside living cells, viruses induce the host cell to synthesize virus particles.
The genome is either DNA or RNA (single or double stranded).
Viruses do not have a system to produce ATP.
Viruses range in size from 25 to 270 nm.
Viral tropism!!
The classification of viruses is based on nucleic acid type, size and shape of virion, and presence or absence of an envelope.
Viral Structure
I . Virion is the entire viral particle.
2. Capsid is the protein coat that encloses the genetic material.
3. Capsomer is the protein subunit that makes up the capsid.
4. Nucleocapsid is composed of the capsid and genetic material.
5. The envelope is the outer coating composed of a phospholipid bilayer, which is composed of viral-encoded glycoproteins and sometimes viral encoded matrix proteins. The envelope is derived from a host cell's membrane.
Some viruses use the plasma membrane, whereas others use endoplasmic reticulum, Golgi, or nuclear membranes. Naked nucleocapsids are viruses with no envelopes.
VIRUSES CLASSIFICATION , LIFE CYCLE OF VIRUSES. CHARACTERISTICS OF VIRUSES Shylesh M
VIRUSES
LIFE CYCLE OF BACTERIOPHAGES
The word virus is derived from Latin word venom which means poisonous fluid that causes infection.
The branch of science that deals with the study of viruses is called Virology. It is the branch of Microbiology.
They show living characters inside the host and non living characters outside the host.
They contain either DNA or RNA as genetic material.
They have different size and shape. They cause diseases in plants, animals and micro-organisms .
Not cellular
Cannot carry on metabolic activities independently.
Contain either DNA or RNA, not both ( true cells contain both ).
Lack ribosomes and enzymes necessary for protein synthesis.
Reproduce only within cells they infect.
CLASSIFICATION OF VIRUSES
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Based on the viral envelope
Named after David Baltimore, a noble prize winning biologist n 1971.
1. dsDNA viruses Eg: Adenoviruses, Herpiviruses.
2. ssDNA viruses Eg: Paravoviruses.
3. dsRNA viruses Eg: Reoviruses.
4. (+)ssRNA viruses Eg: Picornaviruses.
5. (-)ssRNA viruses Eg: Orthomyxoviruses.
6. ssRNA-RT viruses Eg: Retroviruses.
7. dsDNA-RT viruses Eg: Hepadnaviruses.
Tobacco mosaic:
Causative agent: Tobacco mosaic virus (TMV)
Symptoms: The leaves of infected plants develop mosaic patches ,it is due to destruction of chlorophyll or due to production of abnormal chlorophyll .blisters appear in the region of dark green spots these may be regular or irregular in advanced stages leaves curl and get distorted.
Adsorption of the virion to the bacterial cell.
Penetration and decoating of the nucleic acid .
Protein synthesis.
Breakdown of bacterial DNA.
Arrest of host cell development.
Replication of phage DNA.
Maturation of infective progeny.
Lysis and release of newly formed phages.
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Classifications of Fungi
Characteristics of all Fungi
Structure of Fungi
Reproduction
Classification of Fungi
Basidiomycota
sexual reproduction occur by basidium , will be present spore is called basidiospore .
Asexual by budding ,fragementation, conidiospores.
Ascomycota
microscopic sexual structure in which nonmotile spores, called ascospores.
Mostly the ascomycota is sexual but some asexual it lacks the ascospore.
Zygomycota
Two spore
mitospores ( or) sporangiospore
chlamitospore (or) zygospore
Deuteromycota
Imperfect Fungi referring to our "imperfect" knowledge of their complete life cycles.
sexual life cycle that is either unknown or absent.
Asexual reproduction is by means of conidia or may be lacking.
culture media
SDA medium – sabouraud dextrose agar
Viral classification and Types of Replication in virus Rakshith K, DVM
Precise presentation on Viral classification and Types of replication in Virus.
Entry of virus
Spread of virus
General steps in a virus replication cycle
Attachment, Penetration, Uncoating, Multiplication
Multiplication of Single-Stranded RNA (ss RNA) Viruses
Multiplication of Double-Stranded RNA (ds RNA) Viruses
Multiplication of Single-Stranded DNA (ss DNA) Viruses
Multiplication of Double-Stranded DNA (ds DNA) Viruses
Release of new virions
Common viral diseases of Bovines
When fresh liquid medium is inoculated with a given number of bacteria and incubated for sufficient period of time, it gives a characteristic growth pattern of bacteria.
If the bacterial population is measured periodically and log of number of viable bacteria is plotted in a graph against time, it gives a characteristic growth curve which is known as growth curve or growth cycle.
Viruses that infect bacteria.
Occur widely in nature in close association with bacteria.
Readily isolated from faeces, sewage and other natural sources.
Tadpole shaped, with hexagonal head and a cylindrical tail.
Head consists of a tightly packed core of ds DNA surrounded by a protein coat or capsid.
The tail composed of a contractile sheath surrounding the hollow core
Terminal base plate having prongs or tail fibres attached.
Obligate intracellular, unable to self-replicate.
Once inside living cells, viruses induce the host cell to synthesize virus particles.
The genome is either DNA or RNA (single or double stranded).
Viruses do not have a system to produce ATP.
Viruses range in size from 25 to 270 nm.
Viral tropism!!
The classification of viruses is based on nucleic acid type, size and shape of virion, and presence or absence of an envelope.
Viral Structure
I . Virion is the entire viral particle.
2. Capsid is the protein coat that encloses the genetic material.
3. Capsomer is the protein subunit that makes up the capsid.
4. Nucleocapsid is composed of the capsid and genetic material.
5. The envelope is the outer coating composed of a phospholipid bilayer, which is composed of viral-encoded glycoproteins and sometimes viral encoded matrix proteins. The envelope is derived from a host cell's membrane.
Some viruses use the plasma membrane, whereas others use endoplasmic reticulum, Golgi, or nuclear membranes. Naked nucleocapsids are viruses with no envelopes.
VIRUSES CLASSIFICATION , LIFE CYCLE OF VIRUSES. CHARACTERISTICS OF VIRUSES Shylesh M
VIRUSES
LIFE CYCLE OF BACTERIOPHAGES
The word virus is derived from Latin word venom which means poisonous fluid that causes infection.
The branch of science that deals with the study of viruses is called Virology. It is the branch of Microbiology.
They show living characters inside the host and non living characters outside the host.
They contain either DNA or RNA as genetic material.
They have different size and shape. They cause diseases in plants, animals and micro-organisms .
Not cellular
Cannot carry on metabolic activities independently.
Contain either DNA or RNA, not both ( true cells contain both ).
Lack ribosomes and enzymes necessary for protein synthesis.
Reproduce only within cells they infect.
CLASSIFICATION OF VIRUSES
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Based on the viral envelope
Named after David Baltimore, a noble prize winning biologist n 1971.
1. dsDNA viruses Eg: Adenoviruses, Herpiviruses.
2. ssDNA viruses Eg: Paravoviruses.
3. dsRNA viruses Eg: Reoviruses.
4. (+)ssRNA viruses Eg: Picornaviruses.
5. (-)ssRNA viruses Eg: Orthomyxoviruses.
6. ssRNA-RT viruses Eg: Retroviruses.
7. dsDNA-RT viruses Eg: Hepadnaviruses.
Tobacco mosaic:
Causative agent: Tobacco mosaic virus (TMV)
Symptoms: The leaves of infected plants develop mosaic patches ,it is due to destruction of chlorophyll or due to production of abnormal chlorophyll .blisters appear in the region of dark green spots these may be regular or irregular in advanced stages leaves curl and get distorted.
Adsorption of the virion to the bacterial cell.
Penetration and decoating of the nucleic acid .
Protein synthesis.
Breakdown of bacterial DNA.
Arrest of host cell development.
Replication of phage DNA.
Maturation of infective progeny.
Lysis and release of newly formed phages.
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Morphology, Classification, Cultivation and Replication of VirusKrutika Pardeshi
This presentation is Useful for B. Pharmacy SEM III Students to study the Topic Fungi According to PCI Syllabus.
It Consist of Morpholoy of Fungi, Cultivation , Replication and Classification of Virud
Virology is the scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
2. Viruses are the smallest known infective
agents and perhaps the simplest form of life.
Viruses do not posses cellular organization
and they do not fall strictly in to the category
of unicellular microorganism.
3. They do not have cellular organization.
They contain only one type of nucleic acid either
DNA or RNA but never both.
They are obligate intracellular parasites.
They lack the enzymes necessary for protein and
nucleic acid synthesis and are dependent for
replication on the machinery of host cells.
They multiply by a complex process and not by
binary fission.
They are unaffected by antibacterial antibiotics.
4.
5. Extracellular infectious viral particle is called ‘Virion’
Viruses are much smaller than bacteria
For a time, they were known as ‘filterable agents’ as they
can pass through filters that can hold back bacteria.
They can not be seen under light microscope hence called
as ‘ultramicroscopic’.
The virus particles seen in this manner are known as
‘elementary bodies’.
Size range: 20-300 nm
Parvovirus: 20 nm (smallest virus)
Pox virus: 300 nm (biggest virus and can be seen under
light microscope)
6. Passing them through collodion membrane
Electron microscopy
Sedimentation in the ultracentrifuge
Comparatative measurements
Shape of the Virus
The overall shape of the virus particle varies in
different groups of viruses.
Most of the animal virus are roughly spherical,
irregular and pleomorphic.
Eg. Pox virus are brick shaped, rabies virus are
bullet shaped, tobacco mosiac virus is rod shaped
7.
8. A. Viral Capsid
Viruses consists of nucleic acid
core surrounded by a protein
called capsid.
Capsid is composed of large
number of capsomer which is
made up of polypeptide
molecules.
The capsid with the
enclosed nucleic acid is known as
nucleocapsid.
9. It protects the viral genome from physical
destruction and enzymatic inactivation by
nucleases in biological material.
It provides the binding site which enable the virus
to attach to specific site on the host cell.
It facilitates the assembly and packaging of viral
genetic informataion.
It serves as a vehicle of transmission from host to
another.
It is antigenic and specific for each viruses
It provides the structural symmetry to the virus
particle.
10. Viral architecture can be grouped into three types based
on the arrangement of morphological subunits.
1. Icosahedral Symmetry
An icosahedral (icosa, meaning 20 in greek) is a polgon
with 12 vertices or corners and 20 facets or sides.
Each facet is in the shape of an equilateral triangle.
Pentagonal capsomers at the
vertices (pentons) and hexagonal
capsomers making up the facets
(hexons)
Eg. Adeno viruses
11. 2. Helical Symmetry
The nucleic acid and capsomers are wound
together in the form of helix or spiral.
Eg. Influenza virus, parainfluenz virus,
rabies virus.
3. Complex Symmetry
Viruses which don not show either icoshedral or
helical symmetry
due to complexity of their
structure are referred to
have complex symmetry.
Eg. Pox viruses
12. Virions may be enveloped and nonenveloped
(naked).
1. Enveloped Virus
The envelop or outer covering of virus containing
lipid is derived from the plasma membrane of the
host cell during the release by budding from the
cell surface.
The envelop is glycoprotein in nature.
Enveloped viruses are susceptible to the action of
lipid solvent such as ether, chloroform and
detergent.
Eg. Herpes virus, Hepatitis B virus, HIV virus
13. 2. Non enveloped virus
Viruses which does not have outer covering.
Naked viruses are more likely to be resistant to
lipid solvents like ether, chloroform and detergent.
Peplomers
In mature virus particle, the glycoproteins often
appear as projecting spikes on the outer surface of
the envelop which are known as peplomers.
A virus may have more than one type of
peplomers. E.g the influenza virus carries two
types of peplomers, the hemagglutinin and
neuraminidase
14. It helps for attachment of virus to the host
cell receptors to initiate the entrance of the
virion into the cell.
It attach to receptors on red blood cells,
causing these cell to agglutinate.
It has enzymatic activity like neuraminidase
which cleave neuraminic acid from host cell
glycoproteins.
It has antigenic properties.
15.
16. Viruses contain a single kind of nucleic acid
either DNA or RNA which encodes the
genetic information necessary for replication
of the virus.
The genome may be single stranded or
double stranded, circular or linear,
segmented or nonsegmented.
According to nucleic acid present, viruses
can be classified in to DNA viruses and RNA
viruses.
17.
18. The genomic information necessary for viral
replication is contained in the viral nucleic acid but
lacking biosynthetic enzymes.
The virus depend on the synthetic machinery of the
host cell for replication.
The viral multiplication follows following steps.
I. Adsorption or Attachment
II. Penetration
III. Uncoating
IV. Biosynthesis
V. Maturation
VI. Release
19. Adsorption or attachment is specific and is
mediated by the binding of virion surface
structure, known as ligands, to receptors of cell
surface.
Eg. In case of Influenza virus, the surface
glycoprotein hemagglutinin binds specifically to
siliac acide residue of glycoprotein receptor
sites of respiratory tract.
In case of HIV surface glycoprotein gp120 acts
as a ligand and binds to CD4 cells of T-
lymphocytes.
20. After binding the virus particle is taken up
inside the cell.
It is occur by system receptor mediated
endocytosis (viropexis).
Most non-enveloped viruses enter by
receptor mediated endocytosis.
Enveloped viruses fuse their membranes
with cellular membranes to deliver the
nucleocapsid or genome directly into the
cytoplasm.
21. This is the process of stripping the virus of its
outer layers and capsid so that the nucleic
acid is released into the cell.
With most viruses uncoating is effected by
the action of lysosomal enzymes of the host
cell.
The genome of DNA viruses except
poxviruses must be delivered into the
nucleus whereas most RNA viruses remain
in the cytoplasm.
22. This phase includes synthesis not merely of
the viral nucleic acid and capsid protein but
also of enzymes necessary in the various
stages of viral synthesis, assembly and
release.
In addition regulator proteins are also
synthesised which serve to shut down the
normal cellular metabolism and direct the
sequential production of viral components.
23. Transcription of messenger RNA (mRNA)
from the viral nucleic acid.
Translation of the mRNA into early proteins
which initiate and maintain synthesis of virus
component.
Replication of viral nucleic acid.
Synthesis of Late or Structural proteins
which are the components of daughter virion
capsid.
24. Assembly of the various viral components
into virions occurs shortly after the
replication of the viral nucleic acid.
It may take place in either the nucleus or
cytoplasm.
In case of enveloped viruses the envelop are
derived from the host cell nuclear membrane
and plasma membrane.
25. Viruses can be released from cells after lysis
of the cell, by exocytosis, or by budding from
the plasma membrane.
Viruses that exist naked nucleocapsid may
be released by the lysis of the host cell or
reverse phagocytosis.
Release of enveloped viruses occur after
budding from the plasma membrane without
killing the host cell.