Principles of Virology, Multi-Volume, ISBN: 9781683670322
13 views 0 purchase
Course
0105103
Institution
Bangladesh University Of Health Sciences
Book
Principles of Virology, Multi-Volume
This document contains elaborate study materials of the Virology course for both Bachelor and Masters level. It covers both General and Systemic Virology. Total page number: 80. There are questions and answers included in various topics like "Cultivation of viruses; Viral genetics and replication; ...
Reference Books
1. Introduction to Modern Virology (7th Ed.)
Wiley-Blackwell Publication
2. Principles and Practices of Clinical Virology (5th Ed.)
Wiley-Blackwell Publication
3. Basic Virology (3rd Ed.)
Wiley-Blackwell Publication
4. Clinical Virology Manual (4th Ed.)
ASM Press
5. Fundamentals of Molecular Virology (2nd Ed.)
By Nicholas H. Acheson
6. Introduction to Modern Virology (6th Ed.)
Blackwell Publishing
1
,2
, Introduction to Virology
Q. Define virus. State the general properties of virus.
Virus: Viruses are non-cellular particles composed of an internal core containing either DNA or RNA (but not
both) covered by a protective protein coat and they are not capable of independent replication, can synthesize
neither their own energy nor their proteins and are too small to be seen in the light microscope.
General properties of virus:
1. Viruses are the smallest infectious agents (size: 20-300 nm in diameter).
2. Viruses are non-cellular particles composed of either DNA or RNA (but not both) covered by a protective
protein coat.
3. Viruses are obligate intracellular parasites. They are inert in the extracellular environment.
4. Viruses multiply by a process known as replication. One virus can replicate to produce hundreds of progeny
viruses.
5. Parasite at genomic level. They can integrate in human genome.
6. Viruses do not have a nucleus, cytoplasm, mitochondria or ribosome.
7. They do not have enzymes for energy production.
8. Cannot synthesize protein due to absence of ribosome.
9. Viruses cannot grow in artificial culture media. They grow only in cell culture media.
10. Viruses are generally resistant to antibiotics.
11. Viruses are sensitive to interferon.
12. They have cell tropism.
13. Viruses can act as a genomic vector.
Nice to know:
Viruses are intracellular parasites: Viruses have no mitochondria and no ribosome. So they cannot generate
energy or synthesize protein due to absence of enzyme. They replicate within the cell by using the enzyme and
energy yielding apparatus of host cells. Because they can reproduce only within cells, viruses are obligate
intracellular parasites.
Intracellular bacteria: The only bacteria that are obligate intracellular parasites are Chlamydiae and and
Rickettsiae. They cannot synthesize sufficient energy to replicate independently.
Q. What are the differences between viruses and bacteria?
Differences between viruses and bacteria:
Traits Virus Bacteria
1. Cells No Yes
2. Size 20-300 nm More than 300 nm e.g., Staphylococcus
1000 nm.
3. Site Intracellular Usually extracellular, some are
intracellular.
4. Nucleic acid Either DNA or RNA, never both Both DNA and RNA
5. Type of nucleus None Prokaryotic
6. Ribosome Absent Present (70s)
7. Nature of outer Protein capsid and lipoprotein Rigid wall containing peptidoglycan.
surface envelope
8. Motility None Some
9. Microscopy Not seen by light microscope Usually seen by light microscope
10. Multiplication Replication or lysogeny Binary fission
11. Culture Cannot be cultured in artificial and Can be cultured in artificial and cell-free
cell-free media. media.
12. Metabolic activity Absent Present
13. Antibiotic sensitivity Resistant Sensitive
14. Interferon sensitivity Sensitive Resistant
3
, Structure of a Virus
Q. Give the structure of a complete virus particle.
Basic structure of a virus: A virus consists of a nucleic acid (either DNA or RNA but never both) covered by a
protective protein coat called a capsid. Some viruses have envelope outside the capsid.
Virus nucleic acids
• Viruses contain either DNA or RNA but never both.
• These DNA and RNA genomes can be either single stranded or double stranded or linear or circular.
• DNA is always a single molecule; RNA can exist either as a single molecule or in several pieces.
• All viruses are haploid except retroviruses, which are diploid.
Capsid: All viruses have a protein coat called a capsid which are composed of repeating subunits called capsomers.
Functions of capsid proteins:
1. Protect the nucleic acid from the host nuclease.
2. Mediate attachment to host cell receptors.
3. Act as antigens that induce antibody formation and active cytotoxic T cells to kill virus-infected cells.
4. Provides the structural symmetry of virus.
Envelope:
• The viral envelope consists of a membrane that contains lipid derived from the host cell and proteins
encoded by the virus. Typically, the envelope is acquired as the virus exits from the cell in a process called
budding.
• Enveloped viruses are less stable then naked viruses.
Functions of envelope:
1. Protection
2. It also helps in attachment to the target cell.
Q. Write short note on: Viral symmetry
Viral symmetry: The arrangement of capsomers gives the virus structure two types of geometric symmetry:
• Icosahedral: In this type of viral symmetry, the capsomers are arranged in 20 triangles that form a
symmetric figure (an icosahedron) with the appropriate outline of a sphere. Viruses that have an
icosahedral nucleocapsid can be either enveloped or naked.
• Helical: In this type of symmetry, the capsomers are arranged in a hollow coil that appears rod-shaped.
All human viruses that have a helical nucleocapsid, are enclosed by an outer membrane called an envelope,
i.e., there are no naked helical viruses.
Q. What do you mean by atypical virus like agents?
Atypical virus like agents: There are four exceptions to a typical virus:
Q. Why non-enveloped viruses are resistant to detergent?
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller KhAbdullah. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.59. You're not tied to anything after your purchase.
