Viruses Rely Entirely on Host Cells
- Viruses cannot reproduce independently.
- They depend entirely on the host cell’s metabolic machinery.
- The lytic cycle is the most direct reproductive strategy, producing large numbers of viral particles in a short time but at the cost of killing the host.
Definition
The Lytic Cycle
The lytic cycle is a viral replication process during which a virus infects a host cell, takes control of its machinery to produce new viral particles, and ultimately causes the host cell to burst (lyse), releasing the newly formed viruses.
The Lytic Cycle: A Step-by-Step Breakdown
- Step 1: Attachment
- Tail fibers or viral attachment proteins bind to complementary receptor molecules on the host cell surface.
- This specificity determines host specificity (why viruses only infect certain cells).
- Step 2: DNA Entry (Penetration)
- The phage injects its double-stranded DNA into the bacterial cell through a syringe-like tail structure.
- The viral DNA enters, while the capsid remains outside.
- Step 3: Biosynthesis (Replication of Viral Components)
- Viral DNA hijacks the host's enzymes and ribosomes, redirecting host metabolism:
- Early genes produce enzymes for viral DNA replication.
- Late genes encode structural proteins (capsid, tail).
