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Quizzes > Science > Biology

Test Your Knowledge: Virus Structure & Function Quiz

Think you know viral structure - the protein coat and envelope? Take this quiz on viruses now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for a virus quiz on a teal background

Calling all microbiology buffs and curious learners: dive into our Ultimate Virus Quiz and discover the intricate world of tiny invaders! This free virus quiz challenges you with a quiz on viruses that covers everything from a piece of genetic material surrounded by a protein coat to how the envelope is entirely formed from viral material. You'll test your grasp of viral structure components and sharpen your skills before any microbiology exam. Ready to level up? Start our comprehensive interactive virus quiz and explore the detailed virus structure labeled guide now!

What is the term for a complete, infectious virus particle outside a host cell?
Envelope
Virus
Capsid
Virion
A virion refers to the fully assembled viral particle that exists outside of host cells and is capable of infecting new cells. It comprises the viral genome enclosed in a protein coat, with or without a surrounding envelope. The term distinguishes the extracellular phase from the intracellular replication phase. Virion - Wikipedia
What is the protein shell that encloses a viral genome called?
Matrix protein
Envelope
Nucleoid
Capsid
The capsid is the protein shell surrounding and protecting the viral genetic material. It is assembled from repeated protein subunits called capsomeres. This structure is essential for stability and delivery of the genome into host cells. Capsid - Wikipedia
Which of the following capsid symmetries is most commonly adopted by many spherical viruses?
Helical
Complex
Icosahedral
Filamentous
Many spherical viruses adopt icosahedral symmetry because it provides a highly stable structure using repeating subunits. Icosahedral capsids consist of 20 equilateral triangular faces and require minimal genetic coding for capsid proteins. This arrangement maximizes internal volume and stability. Icosahedral symmetry - Wikipedia
What component must all viruses possess to carry their genetic information?
Protein capsid
Enzymes
Lipid envelope
Nucleic acid
All viruses require nucleic acids - either DNA or RNA - to encode their genetic information. This differentiates them from other pathogens like prions or viroids. While many viruses are also enclosed by protein capsids or envelopes, these are not universal. Viral Genome - NCBI
Which structure present in some viruses helps them fuse with host cell membranes?
Capsid
Tail fibers
Envelope
Tegument
Enveloped viruses acquire a lipid bilayer from the host cell membrane that contains viral glycoproteins. These glycoproteins mediate fusion with host cell membranes during entry. Non-enveloped viruses lack this fusion mechanism and use other entry strategies. Enveloped virus - Wikipedia
What is the term for the protein subunit that assembles to form the capsid?
Protein coat
Capsid protein
Nucleocapsid
Capsomere
A capsomere is the individual protein subunit that assembles into the larger capsid structure. Multiple capsomeres interlock to protect the viral genome. Identifying capsomeres is crucial for understanding capsid assembly. Capsomere - Wikipedia
What is the role of viral attachment proteins?
Assemble capsid proteins
Provide energy for replication
Bind to host cellular receptors
Replicate viral genome
Viral attachment proteins, often called spikes, recognize and bind specific receptors on host cells. This binding is the first step in viral entry. Without these interactions, the virus cannot infect the cell. Virus Entry
What type of genetic material can be found in viruses?
Only RNA
Proteins
Either DNA or RNA
Only DNA
Viruses use nucleic acids - either DNA or RNA - to encode their genetic information, unlike cellular organisms which typically use both. They can be single- or double-stranded. No virus uses proteins as its genetic material. Viral genome - Wikipedia
The lipid bilayer surrounding some viruses is derived from which of the following?
Golgi apparatus membrane
Host cell membrane
Bacterial cell wall
Mitochondrial membrane
Enveloped viruses bud from the host cell plasma membrane, acquiring a lipid bilayer in the process. Some viruses can also bud from internal membranes, but the plasma membrane is most common. This envelope contains viral glycoproteins essential for entry. Enveloped virus - Wikipedia
Which of the following viral genomes can act directly as mRNA upon infection?
Single-stranded DNA
Negative-sense single-stranded RNA
Positive-sense single-stranded RNA
Double-stranded DNA
Positive-sense single-stranded RNA genomes function directly as mRNA in the host cell, allowing immediate translation. Negative-sense RNA must first be transcribed to positive-sense by a viral polymerase. DNA viruses require transcription in the nucleus. Baltimore classification - Wikipedia
What is the function of the viral matrix protein in enveloped viruses?
Connects envelope glycoproteins to the nucleocapsid
Assists in genome replication
Synthesizes viral RNA
Mediates host cell receptor binding
The matrix protein lies beneath the viral envelope and links surface glycoproteins to the internal nucleocapsid. This interaction is critical for proper virion assembly and budding. It also helps maintain structural integrity. Viral matrix protein - Wikipedia
Retroviruses are unique among RNA viruses because they contain which enzyme?
Reverse transcriptase
RNA polymerase
Integrase
Protease
Reverse transcriptase allows retroviruses to convert their RNA genome into complementary DNA (cDNA) for integration into the host genome. While integrase is also present, it acts on the DNA intermediate rather than mediating reverse transcription. No other major RNA virus group carries reverse transcriptase. Reverse transcriptase - Wikipedia
Viruses that package their genome in multiple separate segments are called what?
Polyploid viruses
Multipartite viruses
Fragmented viruses
Segmented viruses
Segmented viruses have genomes divided into distinct segments, each encoding different genes. Influenza virus is a classic example with eight RNA segments. Multipartite viruses carry segments in separate particles, whereas segmented viruses package all segments in one virion. Segmented virus genome - Wikipedia
Influenza viruses assemble and bud primarily at which cellular site?
Golgi apparatus
Plasma membrane
Nucleus
Endoplasmic reticulum
Influenza viruses assemble their components at the host cell plasma membrane and bud from this site. Viral glycoproteins are transported to the membrane via the secretory pathway. Although replication of viral RNA occurs in the nucleus, assembly and release occur at the cell surface. Influenza virus - Wikipedia
Envelope glycoproteins do NOT have which of the following functions?
Antigenic variation
Fusion with host membrane
Mediating host cell entry
Catalyze nucleic acid polymerization
Envelope glycoproteins facilitate receptor binding, membrane fusion, and can exhibit antigenic variation to evade immune detection. They do not catalyze polymerization of nucleic acids - that function is performed by viral polymerases inside the virion or within the host cell. Viral glycoprotein - Wikipedia
How do bacteriophages typically introduce their genome into bacterial cells?
Tail contraction injects the genome
Fusion with the bacterial membrane
Exocytosis
Endocytosis
Many bacteriophages bind to bacterial cell receptors and then contract a tail sheath to drive their genome through the cell wall and membrane. This injection process is mechanically driven and does not involve membrane fusion or endocytosis. It is a hallmark of tailed phages like T4. Bacteriophage - Wikipedia
What is the viral tegument and where is it located?
A protein layer between the capsid and envelope
A nucleic acid complex in the core
A lipid layer outside the envelope
A protein coat around the viral genome
The tegument is a proteinaceous layer found in enveloped viruses like herpesviruses, located between the capsid and the viral envelope. It contains proteins that aid in early stages of infection and modulate host immune responses. Tegument proteins are delivered into the host cell upon fusion to facilitate viral replication. Herpesviral tegument - Wikipedia
What drives the self-assembly of icosahedral viral capsids?
Host chaperone proteins
Viral RNA
Interactions between capsomere subunits
ATP energy
Icosahedral capsids self-assemble through specific non-covalent interactions among capsomere subunits. This process is often spontaneous and does not require external energy input or host chaperones. The result is a stable icosahedral shell that encloses the viral genome. Viral Capsid Assembly - NCBI
Which motif is characteristic of class I viral fusion proteins?
Leucine zipper
Zinc finger
Heptad repeat region forming a coiled-coil
Beta-barrel domain
Class I fusion proteins feature heptad repeat regions that form coiled-coil structures during the fusion process. This conformational change brings viral and host membranes close together, facilitating fusion. Examples include influenza hemagglutinin and HIV gp41. Viral fusion protein - Wikipedia
In negative-sense single-stranded RNA viruses, viral RNA is always encapsidated by which protein?
Nucleoprotein
Polymerase
Matrix
Capsid
Negative-sense RNA viruses tightly associate their genome with nucleoproteins to form a ribonucleoprotein complex. This encapsidation is essential for genome stability and recognition by the viral polymerase. The polymerase itself also associates but the nucleoprotein specifically coats the RNA. Ribonucleoprotein - Wikipedia
Quasi-enveloped viruses refer to:
Viruses that switch between enveloped and non-enveloped forms
Viruses with incomplete envelopes
Viruses that lose their envelope at high temperatures
Viruses released in vesicles without acquiring viral envelope glycoproteins
Quasi-enveloped viruses, such as hepatitis A and E, are released in host-derived vesicles lacking viral glycoproteins, so they appear non-enveloped but have a lipid bilayer. They evade immune detection by cloaking themselves in host membranes. These vesicles are distinct from classic viral envelopes. Quasi-enveloped viruses - NCBI
What structural feature primarily determines a virus's host range?
Genome type
Capsid symmetry
Site of replication
Viral attachment proteins' receptor specificity
A virus's host range is chiefly determined by the affinity of its attachment proteins for specific receptors on target cells. If the viral spike proteins cannot bind a receptor, infection cannot occur. Other factors like internal replication machinery also influence host range but receptor binding is key. Host range - Wikipedia
Poxviruses have a unique core structure described as:
Icosahedral core
Spherical core
Helical core
Dumbbell-shaped core
Poxvirus particles contain a distinctive dumbbell-shaped core within their brick-shaped virions. This core houses the viral genome and associated enzymes. Its unique morphology sets poxviruses apart from other viral families. Poxviridae - Wikipedia
Which component of bacteriophage T4 recognizes and binds to host cell surface receptors?
Envelope glycoproteins
Tail fibers
Matrix proteins
Capsid spikes
Bacteriophage T4 uses long tail fibers to recognize and bind specific receptors on the E. coli cell surface. Following binding, conformational changes trigger sheath contraction and genome injection. Tail fibers are critical for host specificity. Bacteriophage T4 - Wikipedia
In an icosahedral virus with T=7 symmetry, how many hexamers are present in the capsid?
420
120
60
12
The Caspar-Klug theory dictates that the number of hexamers in an icosahedral capsid equals 10 × (T ? 1). For T=7, this gives 10 × 6 = 60 hexamers. There are always 12 pentamers in any icosahedral virus regardless of T number. Caspar - Klug theory - Wikipedia
What role do scaffolding proteins play during viral assembly?
Form part of the mature virion
Mediate host cell recognition
Replicate viral genome
Guide proper capsid assembly and are removed during maturation
Scaffolding proteins assist in organizing and correctly assembling capsid subunits into a procapsid. They are typically not part of the final mature virion and are removed during maturation or proteolytic cleavage. Their transient presence ensures accurate capsid geometry. Viral assembly - NCBI
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Study Outcomes

  1. Identify Core Viral Structures -

    Describe a piece of genetic material surrounded by a protein coat (capsid) and explain its significance in virus architecture.

  2. Differentiate Viral Genome Types -

    Compare and contrast DNA and RNA genomes to understand how genome type influences viral replication.

  3. Analyze Viral Envelope Formation -

    Explain how the envelope is entirely formed from viral material and assess its role in host cell interaction.

  4. Classify Viruses by Morphology -

    Apply your knowledge from this virus quiz to categorize viruses based on their structural components and envelope presence.

  5. Evaluate Structural Impact on Infectivity -

    Assess how features like the capsid and envelope contribute to viral infectivity and pathogenicity.

Cheat Sheet

  1. Fundamental Definition of a Virus -

    Viruses are best described as a piece of genetic material surrounded by a protein coat, which is the core descriptor you'll encounter in every virus quiz (CDC Virology Basics). A simple memory hack is "G&P" - Genetic material & Protein coat - to lock in this two-part definition. Mastering this lays the groundwork for understanding more complex structures like capsids and envelopes.

  2. Genome Types & Baltimore Classification -

    Viruses fall into seven Baltimore groups based on genome composition (ssDNA, dsDNA, ssRNA+, ssRNA - , dsRNA) and replication strategy (David Baltimore, 1971). A helpful study trick is to pair each group with a representative virus: Group I = Herpesvirus (dsDNA), Group IV = Poliovirus (ssRNA+), and so on. Keep this chart handy when tackling a quiz on viruses to quickly match structure to replication pathway.

  3. Capsid Architecture: Helical vs Icosahedral -

    Capsids organize into helical rods (e.g., Tobacco Mosaic Virus) or icosahedral shells (e.g., Adenovirus), and recognizing these geometries boosts confidence on visualization questions. Remember "H for Helix, I for Ico-ttagon" to recall the two main shapes, and apply the triangulation formula T = h² + hk + k² to compute subunit numbers (poliovirus is T = 3). This insight is often tested in advanced viral structure sections.

  4. Viral Envelope Composition & Function -

    Although enveloped viruses steal a lipid bilayer from the host membrane, the envelope is entirely formed from viral material in terms of glycoprotein content and structure (NIH Virology Review). These spikes mediate receptor binding and membrane fusion, making the envelope a key focus in many quiz questions. Use the phrase "spike, bind, fuse" to remember its three critical roles in infection.

  5. Six-Step Replication Cycle & Mnemonic -

    Viral replication follows six stages - Attachment, Entry, Uncoating, Genome replication, Assembly, and Release - that frequently appear in exam questions (Microbiology Society). A clever acronym is A-E-U-G-A-R, pronounced "ay-you-gar," to recall the sequence effortlessly. Recall that influenza enters via endocytosis and buds out at Release to tie each step back to structural features.

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