A2.3 Viruses Flashcards
What is the size range of viruses?
20nm - 300nm
Viruses are notably small compared to other microorganisms.
What type of genetic material can viruses contain?
DNA or RNA
This genetic material is essential for the virus’s replication and function.
What is a capsid?
A protein coat that coats the genetic material
The capsid protects the viral genome and aids in the infection of host cells.
Do viruses contain cytoplasm?
No
Viruses lack cellular structures and rely on host cells for their metabolic processes.
Do viruses have enzymes?
Few/No
Viruses do not require their own enzymes as they depend on the host cell’s machinery.
What are some structural variances among viruses?
Size, type of genetic material, single/double stranded genome, circular/linear genome, genes present, size of genome, capsid shape, presence of lipid envelope
These variances contribute to the diversity of viruses.
On what basis are viruses classified?
Type of genetic material, linear or circular, double stranded or single stranded
This classification helps in understanding the characteristics and behavior of different viruses.
What are the primary aims of a virus within a host cell?
Make more virus DNA/RNA, make more virus proteins, assemble new virus molecules
These processes are essential for the replication and propagation of the virus.
What are the predominant shapes of virus capsids?
Helical or icosahedral
Some viruses have complex capsid structures that do not fit these categories.
What is the significance of a lipid bilayer membrane in viruses?
Indicates the presence or absence of a virus envelope
The lipid bilayer membrane is acquired from host cell membranes during virus maturation.
How do enveloped viruses acquire their lipid bilayer membrane?
Through the process known as ‘budding’
Budding occurs during the maturation of the virus.
What is the most common exit method for non-enveloped viruses from the host cell?
Cell lysis
This occurs due to the lack of an extra lipid membrane.
What advantages do non-enveloped viruses have?
More resistant to extreme pH, heat, dryness, and simple disinfectants
Their structure allows them to endure harsher environmental conditions.
What typically follows the replication of enveloped viruses?
Cell death often follows as a consequence of virus replication
Lysis is not guaranteed but often occurs.
What is the process called by which enveloped viruses exit the host cell?
‘Budding’
This process allows enveloped viruses to acquire their lipid bilayer.
How do enveloped viruses compare to non-enveloped viruses in terms of environmental sensitivity?
Enveloped viruses are more sensitive to extreme pH, heat, dryness, and simple disinfectants
Their lipid bilayer makes them less resilient than non-enveloped viruses.
What are bacteriophages?
Intracellular viruses that specifically infect bacteria.
What is the first step in the lytic cycle of a bacteriophage?
Phage attachment to a receptor protein within the bacterial cell membrane.
How does initial contact between phage and bacterial cell occur?
Through random collisions.
True or False: Not all bacteria-phage combinations have compatible receptors.
True.
What mechanism do phages use to inject their genetic material into a bacterial cell?
Phage tail contraction.
What structure often surrounds the tube used for delivering genetic material in phages?
A sheath of contractile proteins.
What happens to the phage DNA once it enters the bacterial cell?
The ends of the linear phage DNA join to form a circle.
What type of replication is used to produce exact copies of phage DNA?
Rolling-circle replication.
