p.13
Receptors Used by Viruses
What do viruses require to infect a cell?
Cells possessing surface receptors specific to particular virus species.
p.7
Viral Proteins and Their Functions
Which viruses produce superantigens?
Epstein-Barr virus and Cytomegalovirus.
p.15
Viral Replication Cycle
How do viruses penetrate into a cell?
By viropexis (pinocytosis).
p.7
Virus Structure and Components
What is the role of matrix protein in viruses?
It mediates interaction between viral nucleocapsid proteins and envelope proteins.
p.15
Viral Replication Cycle
What is a key difference in penetration between enveloped and non-enveloped viruses?
Enveloped viruses fuse with the cell membrane, while non-enveloped viruses use different mechanisms.
p.9
Viral Envelope and Its Properties
How is the viral envelope acquired?
As the virus exits from the cell in a process called budding.
p.15
Viral Replication Cycle
What happens to the envelope of enveloped viruses during penetration?
The envelope fuses with the cell membrane, releasing the virus into the cytoplasm.
p.13
Viral Structure and Components
What are the two types of structures that allow viruses to attach to cells?
Capsid (for naked viruses) and envelope proteins (for enveloped viruses).
p.1
Characteristics of Viruses
What are viruses classified as?
Obligate intracellular parasites.
p.10
Viral Envelope and Its Properties
How do naked viruses differ from enveloped viruses in terms of sensitivity?
Naked viruses are resistant to heat and dryness.
p.4
Capsid and Nucleocapsid
What is the composition of the capsid?
It is composed of protein.
p.1
Characteristics of Viruses
Do viruses synthesize their own energy or proteins?
No, they synthesize neither their energy nor their proteins.
What is the size range of viruses?
Approximately 20 nm to 300 nm.
p.4
Capsid and Nucleocapsid
What is the function of the capsid in viruses?
To cover and protect the viral genome from nucleases.
What does the latent period represent in the context of viral infection?
The time from the onset of infection to the appearance of the virus extracellularly.
p.6
Viral Proteins and Their Functions
What types of polymerases can internal proteins be?
They can be DNA or RNA polymerases.
p.8
Viral Proteins and Their Functions
What types of factors do regulatory proteins include?
Transcription and translation factors.
p.10
Viral Envelope and Its Properties
What is a key property of enveloped viruses?
They are sensitive to heat and dryness.
p.5
Virus Structure and Components
Which DNA virus is an exception to the icosahedral structure?
Poxvirus, which has a complex capsid.
p.6
Viral Proteins and Their Functions
What strategy do some viruses use to evade host defenses?
They produce antigenic variants of their surface proteins.
p.9
Viral Envelope and Its Properties
What does the lipid bilayer of a viral envelope contain?
Viral glycoproteins and lipids derived from the host cell.
p.7
Viral Proteins and Their Functions
What is the effect of superantigens on T cells?
They cause non-specific polyclonal activation of T cells.
What occurs to viral nucleic acid during the decline phase?
Viral nucleic acid continues to function and begins to accumulate within the cell, represented by a dotted line.
p.5
Virus Structure and Components
How are capsomers arranged in helical viruses?
They are arranged in a hollow coil that appears rod-shaped.
p.6
Viral Proteins and Their Functions
What are the two main types of viral proteins?
Surface proteins and internal proteins.
What happens to the virus particles during the decline phase of the viral growth curve?
The virus disappears and is no longer present, indicated by a solid line dropping to the x-axis.
p.5
Virus Structure and Components
What shape do capsomers form in icosahedral viruses?
They are arranged in 20 triangles that form a symmetric figure (icosahedron) with an approximate outline of a sphere.
What are the possible structures of viral genomes?
Single-stranded or double-stranded.
What are the two main transmission routes for viruses?
Direct via blood & body fluids and indirect, e.g., fecal-oral route.
p.1
Characteristics of Viruses
How small are viruses compared to cells?
Very small; they are not seen by light microscopes.
p.16
Viral Replication Cycle
What activates the uncoating process?
Cellular enzymes and contributions from cell membranes (except for smallpox virus).
p.13
Viral Replication Cycle
What is the first step in the viral replication cycle?
Attachment to the host cell.
p.1
Characteristics of Viruses
Can viruses replicate independently?
No, they are not capable of independent replication.
What is the eclipse period in the viral growth curve?
The time during which no virus is found inside the cell, ending with the appearance of the virus.
p.12
Viral Replication Cycle
What is the fourth event in the viral growth cycle?
Gene expression & Genome replication.
p.10
Viral Characteristics
What is the difference between less virulent and more virulent viruses?
Less virulent viruses cause milder infections, while more virulent viruses cause severe disease.
p.8
Virus Structure and Components
What structure contains regulatory proteins in some viruses like herpes simplex virus?
Tegument, located between the nucleocapsid and envelope.
p.8
Viral Proteins and Their Functions
What processes do regulatory proteins control?
Either viral or cellular processes.
p.6
Viral Proteins and Their Functions
What is the role of surface proteins in viruses?
They mediate attachment to host cell receptors.
p.10
Viral Envelope and Its Properties
What is the effect of organic solvents like alcohol on enveloped viruses?
They cause rapid inactivation due to the presence of a lipid bilayer.
p.4
Capsid and Nucleocapsid
What gives the capsid its symmetric appearance?
The arrangement of capsomers.
p.14
Receptors Used by Viruses
Which receptor is targeted by Parvovirus B19?
P antigen on erythrocytes.
What is unique about the genome of retroviruses?
They have two copies, i.e., diploid.
What type of nucleic acids do viruses contain?
Either DNA or RNA, but not both.
p.6
Viral Proteins and Their Functions
How do antibodies affect viral replication?
Antibodies target viral proteins, inhibiting viral replication.
p.5
Virus Structure and Components
What are the two forms of symmetry found in viral nucleocapsids?
Icosahedral and helical symmetry.
p.4
Capsid and Nucleocapsid
What does the term 'nucleocapsid' refer to?
The capsid and the enclosed nucleic acid.
Which RNA viruses have segmented genomes?
Influenza virus and rotavirus.
p.10
Viral Characteristics
What does it mean for a virus to be virulent?
It refers to the degree of pathogenicity or ability to cause disease.
p.14
Receptors Used by Viruses
What receptor does the Rabies virus bind to?
Nicotinic acetylcholine receptor.
