Podcast
Questions and Answers
What is the primary genetic material found in viruses?
What is the primary genetic material found in viruses?
Which of the following statements is true regarding viruses?
Which of the following statements is true regarding viruses?
What components make up a virus?
What components make up a virus?
What are virions primarily responsible for?
What are virions primarily responsible for?
Signup and view all the answers
Which characteristic distinguishes enveloped viruses from non-enveloped viruses?
Which characteristic distinguishes enveloped viruses from non-enveloped viruses?
Signup and view all the answers
Which statement is true regarding viroids?
Which statement is true regarding viroids?
Signup and view all the answers
Which of the following is a reason viruses are considered acellular infectious organisms?
Which of the following is a reason viruses are considered acellular infectious organisms?
Signup and view all the answers
What distinguishes prions from viruses and viroids?
What distinguishes prions from viruses and viroids?
Signup and view all the answers
Which of the following is NOT a property of virions?
Which of the following is NOT a property of virions?
Signup and view all the answers
What is a notable characteristic of viruses compared to most bacteria?
What is a notable characteristic of viruses compared to most bacteria?
Signup and view all the answers
Study Notes
Virus Structure and Classification
- Viruses are small infectious agents that replicate only inside living cells of other organisms (bacteria, plants, animals, and humans).
- They consist of genetic material (DNA or RNA) surrounded by a protein coat (capsid).
- Some viruses have an additional outer layer called an envelope, derived from the host cell membrane.
- Viruses are not considered living organisms because they cannot reproduce independently.
- They use the host cell's machinery to replicate.
- The viral particles are also called virions.
Virus Objectives
- Describe basic virus properties
- Understand virus structure and classification
- Differentiate between viruses, viroids, and prions
- Differentiate between enveloped and non-enveloped viruses
What is a Virus?
- Viruses are small infectious agents.
- They can infect many organisms.
- Viral genetic material (DNA or RNA) is enclosed within a protein coat.
- Virus particles are too small to be seen with a light microscope.
- They are only visible by an electron microscope.
Virus Properties
- Viruses are microscopic infectious agents.
- Their size ranges from 20-200 nanometers.
- They are acellular (not made of cells).
- They are obligate intracellular parasites. (Can only reproduce inside living cells.)
- They use host cell machinery for replication and protein synthesis.
- Viruses cannot carry out independent metabolism; they depend on host cells for energy.
- Viruses do not have their own ribosomes.
- They cannot make proteins or energy by themselves.
Virus
- A virus is a small infectious agent that lacks independent metabolic function and cannot replicate outside its host.
- Common examples of viruses include rhinovirus (the common cold), influenza virus (the flu), and HIV (human immunodeficiency virus).
Infectious Particles of a Virus (Virion)
- Virions are complete infectious virus particles.
- They are formed inside host cells.
- They include genetic material (DNA or RNA) enclosed in a protein coat (capsid).
- Some virions have an additional envelope made from host cell membrane.
- Virions do not grow.
- They transmit viral genomes from cell to cell.
- They protect viral genomes in harsh environments.
Viroids and Prions
- Viroids are the smallest known pathogens.
- They are composed of a single-stranded circular RNA molecule without protein.
- Viroids mainly affect plants.
- Prions are infectious agents composed entirely of protein.
- They lack nucleic acid (DNA or RNA).
- Prions cause diseases like kuru & Creutzfeldt-Jakob Disease (CJD).
Virus Facts
- Viruses are generally more resistant to some disinfectants than bacteria.
- They are not affected by antibiotics.
Structure of Viruses
- Each virus consists of genetic material (DNA or RNA) and a protein coat (capsid).
- The capsid surrounded nucleic acid is called a nucleocapsid.
- Some viruses have an outer envelope derived from host cell membranes.
Basic Virus Structure
- A virus consists of a capsid composed of protein subunits, surrounding the genetic material (nucleic acid).
- Lipid membrane and glycoproteins form the outer layer of a virus.
- The combination of nucleic material and the capsid forms the nucleocapsid
- The presence of an outer lipid envelope makes it enveloped.
- Enveloped viruses are often more sensitive to heat, detergents, and acids.
Capsid (Coat)
- Capsid is the protective protein coat around the virus' genetic material. (DNA or RNA)
- It is critical for viral attachment to host cells.
- Capsids are assembled from individual protein subunits, called capsomeres.
- Function to protect the nucleic acid genome.
- Allow release of nucleic acid into a host cell.
- Helps stimulate the host's immune system.
Virus Envelope
- It's a membrane that surrounds some viruses, enhancing entry to and exit from the host cell.
- These envelopes are derived from host cell membranes.
- It contains glycoproteins providing viral specificity for host cells.
Enveloped Viruses
- Enveloped viruses have an outer envelope on top of the nucleocapsid.
- The envelope is derived from the host cell membrane.
- Enveloped viruses are susceptible to drying, heat, and detergents.
Non-Enveloped Viruses
- These viruses lack an envelope.
- Their capsid structure is the outermost layer around genetic material.
- Naked viruses are more resistant to harsh environmental conditions (heat, detergents).
- They are less susceptible to disinfectants.
Viral Properties
- Viruses can have DNA or RNA as genetic material, not both.
- The protein coat (capsid) surrounds the genetic material.
- The nucleocapsid is the capsid combined with the nucleic acid.
- An external viral envelope may be present, made from host cell membranes.
- Viruses lack their own replicative machinery and ribosomes.
Classification of Viruses
- Viruses are classified based on their genetic material (DNA or RNA).
- The virus genome can be single- or double-stranded, linear or circular.
- Viruses can be further classified according to their shape, presence/absence of an envelope, or type of host.
- Some viruses have their own enzyme for genome replication, while others use host-cell enzymes.
Classification of Viruses by Capsid Structure
- Naked icosahedral
- Enveloped icosahedral
- Enveloped helical
- Naked helical
- Complex
Classification of Viruses on the Basis of Shape
- Most animal viruses are roughly spherical.
- Rabies virus is bullet-shaped.
- Ebola virus is filamentous.
- Poxvirus is brick-shaped.
- Adenovirus is space-vehicle shaped.
Classification of Viruses Based on Host
- Animal viruses
- Plant viruses
- Bacteriophages (viruses that infect bacteria)
Additional Information (General)
- Viruses generally infect only specific cell types based on surface proteins.
- Some viruses require both humoral and cellular immune responses.
- Certain viruses insert viral proteins into host cell membranes.
- These proteins can help the virus infect other host cells.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the fundamental properties and structures of viruses, including their classification, the differences between viruses and other infectious agents, and the nature of enveloped versus non-enveloped viruses. Test your understanding of these essential concepts in virology.
