Virus Structure Overview
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Questions and Answers

What are the main components that make up a virus?

Viruses are primarily made of nucleic acids, proteins, and sometimes lipids.

What is the significance of the capsid in the structure of a virus?

The capsid protects the viral nucleic acid and aids in the virus's ability to infect host cells.

How do viruses differ from living organisms regarding reproduction?

Viruses cannot reproduce on their own and require a host cell to replicate.

What types of nucleic acid can be found in viruses?

<p>Viruses can contain double-stranded DNA, single-stranded DNA, double-stranded RNA, or single-stranded RNA.</p> Signup and view all the answers

What is the role of the outer lipid envelope in some viruses?

<p>The outer lipid envelope helps the virus evade the host's immune system and facilitates entry into host cells.</p> Signup and view all the answers

In what ways are viral genomes unique compared to cellular genomes?

<p>Viral genomes show more variety in structure and composition, being much smaller and often segmented or circular.</p> Signup and view all the answers

What does it mean for a virus to be classified as acellular?

<p>Acellular means that viruses lack cellular structures and are not composed of cells.</p> Signup and view all the answers

How do viruses obtain energy since they are considered nonliving?

<p>Viruses do not transform energy; they rely completely on host cells for energy and replication.</p> Signup and view all the answers

What distinguishes cellular microorganisms from acellular infectious particles?

<p>Cellular microorganisms are living organisms capable of carrying out life processes, while acellular infectious particles, like viruses, are not living and cannot perform these processes.</p> Signup and view all the answers

Can viruses be classified as living organisms? Why or why not?

<p>No, viruses cannot be classified as living organisms because they cannot carry out all life processes independently.</p> Signup and view all the answers

What are the two domains of prokaryotes?

<p>The two domains of prokaryotes are Archaea and Eubacteria.</p> Signup and view all the answers

What size can viruses typically only be seen with?

<p>Viruses can only be seen with an electron microscope due to their small size, generally around 1 μm (1000 nm) or smaller.</p> Signup and view all the answers

What domain do eukaryotic cells belong to?

<p>Eukaryotic cells belong to the domain Eukaryota.</p> Signup and view all the answers

What is one key feature that differentiates viruses from the other types of cellular organisms?

<p>Viruses lack cellular structures and are unable to perform metabolic processes on their own.</p> Signup and view all the answers

Which microscope is required to view viruses due to their size?

<p>An electron microscope is required to view viruses due to their small size.</p> Signup and view all the answers

What is meant by the term 'acellular infectious particles'?

<p>'Acellular infectious particles' refer to infectious agents, such as viruses, that do not have a cellular structure.</p> Signup and view all the answers

What is the primary function of the viral capsid?

<p>To protect the viral nucleic acid and facilitate attachment to host cells.</p> Signup and view all the answers

What are capsomeres?

<p>Capsomeres are the protein subunits that make up the viral capsid.</p> Signup and view all the answers

What macromolecule primarily composes the viral envelope?

<p>The viral envelope is primarily made of lipids.</p> Signup and view all the answers

How do envelope proteins and glycoproteins assist a virus?

<p>They play a significant role in host recognition and attachment.</p> Signup and view all the answers

What distinguishes a naked virus from an enveloped virus?

<p>A naked virus lacks a viral envelope and consists only of the capsid and genetic material.</p> Signup and view all the answers

Can viruses have multiple types of capsomeres in their capsid?

<p>Yes, some viruses have capsids composed of multiple types of capsomeres.</p> Signup and view all the answers

What is a helical virus structure?

<p>A helical virus has a capsid that forms a rod-like structure, coiling around its nucleic acid.</p> Signup and view all the answers

Name one function of the viral envelope obtained from the host cell.

<p>It aids in evading the host's immune response.</p> Signup and view all the answers

Flashcards

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What are viruses?

Viruses are acellular infectious particles that are too small to be seen with a light microscope and can only be seen with an electron microscope. They lack the ability to carry out all life processes, making them not considered living organisms.

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What are the two main categories of microorganisms?

Microorganisms can be divided into two main categories: cellular microorganisms and acellular infectious particles.

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Examples of cellular microorganisms

Cellular microorganisms include prokaryotes (Archaea and Eubacteria) and eukaryotes (Eukaryota).

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Acellular infectious particles

Acellular infectious particles are not made up of cells and are incapable of carrying out all life processes on their own. Viruses are the most well-known example.

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What is the difference between prokaryotes and eukaryotes?

Prokaryotes are single-celled organisms that lack a nucleus and membrane-bound organelles. Eukaryotes have a nucleus and other membrane-bound organelles.

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Why are viruses not considered living organisms?

Viruses lack the ability to carry out all of the functions required for life, such as metabolism, reproduction, and response to stimuli. They depend on host cells for these processes.

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Virus structure

Viruses consist of a nucleic acid core (DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an envelope.

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How are viruses classified?

Viruses are classified based on their genetic material (DNA or RNA), shape, and host range.

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Viral Genome

The genetic material of a virus is its genome. It can be DNA or RNA, single-stranded or double-stranded, linear or circular. Viral genomes are much smaller than those of cells.

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Virus Reproduction

Viruses cannot reproduce on their own. They need to infect a host cell to replicate. They use the host cell's machinery to make new viral components and assemble new viruses.

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Why are viruses different from cells?

Viruses are not made of cells and cannot reproduce on their own. They also lack the machinery for protein synthesis, which is essential for cell function.

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What are viruses made of?

Viruses are composed of nucleic acid (DNA or RNA), a protein coat called a capsid, and sometimes an outer envelope made of lipids and proteins.

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How do scientists categorize viruses?

Viruses are categorized based on their genetic material (DNA or RNA), their genome structure (linear, circular, segmented), and the type of host they infect.

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Viral Capsid

A protein coat that protects the virus's genetic material and helps it attach to host cells.

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Capsomeres

The protein subunits that make up the viral capsid.

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Viral Envelope

A membrane surrounding some viruses, acquired from the host cell during viral release.

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Viral Envelope Composition

The viral envelope primarily consists of phospholipids, proteins, and glycoproteins.

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Viral Glycoproteins (Spikes)

Proteins on the viral envelope that often help the virus recognize and bind to its host.

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Naked Virus

A virus without an envelope, relying solely on its capsid for protection.

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Helical Capsid

A viral capsid shaped like a long, hollow cylinder, often found in viruses like Tobacco Mosaic Virus.

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Polyhedral Capsid

A viral capsid shaped like a many-sided geometric figure, often resembling an icosahedron.

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Study Notes

Viral Structure

  • Viruses are composed of genetic material (DNA or RNA) enclosed within a protective protein coat called a capsid.

  • Capsid provides structure and protection for the viral genome, allowing viruses to survive outside of a host cell.

  • The capsid is made up of individual protein subunits called capsomeres

  • Some viruses possess an **outer ** lipid envelope derived from the host cell membrane during viral assembly.

  • Envelope proteins and glycoproteins embedded in the envelope facilitate viral attachment to host cells and immune evasion.

  • Naked viruses lack an envelope and are therefore more resistant to environmental factors.

Viral Reproduction

  • Viruses are obligate intracellular parasites, meaning they cannot reproduce independently and require a host cell for replication.

  • Viral replication involves various stages:

    • Attachment to host cells
    • Entry into host cells
    • Replication of the viral genome
    • Assembly of new viral particles
    • Egress or release of newly formed viruses.

Viral Genome

  • Viral genomes can be DNA or RNA.

  • Viral DNA can be single-stranded (ss) or double-stranded (ds).

  • Viral RNA can be ss or ds and may be further categorized as positive-sense or negative-sense.

  • Positive-sense RNA can directly serve as mRNA for protein synthesis.

  • Negative-sense RNA requires transcription into a complementary strand before protein synthesis can occur.

Viral Classification

  • Viruses are acellular infectious particles meaning they lack the features of a living cell such as organelles, cytoplasm, or a plasma membrane.

  • Viruses are not classified as living organisms because they cannot reproduce independently, lack cellular structures, and cannot carry out metabolism.

  • They are classified as non-living entities.

Cellular vs Acellular Organisms

  • Cellular microorganisms (bacteria, archaea, and eukaryotes) are defined by their cellular structure.

  • Acellular infectious particles (viruses, viroids, and prions) lack cellular structures and are considered non-living.

Domains of Prokaryotes

  • The two domains of prokaryotes are Bacteria and Archaea.

Microscope Required to View Viruses

  • Viruses are generally too small to be seen with a light microscope.

  • Electron microscopes are required to visualize viruses.

Key Features Differentiating Viruses

  • The lack of cellular structures defines viruses as acellular infectious particles.

  • Their unique replication strategy of relying on host cells for reproduction contributes to their categorization as non-living entities.

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Virus Structure PDF

Description

Explore the fundamental structure of viruses in this quiz. Learn how viruses differ from living organisms and their unique characteristics. This quiz presents key concepts that will enhance your understanding of virology.

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