Viral Infectious Cycles – Lytic (pkt pg 12) AND Lysogenic (pkt pg 13) Virus - protein coat (capsid) nucleic acid (DNA or RNA) attachment proteins

Lytic Cycle Step 1 – Adsorption Step 2 – Entry Attachment proteins “connect” by fitting the shape of plasma membrane receptor proteins; “tricking” the cell Step 2 – Entry Can be EITHER the whole virus OR the nucleic acid injected Virus is invading the host cell

Lytic Cycle Virus immediately takes over metabolic activity of the cell (host) Cell no longer functions normally Organism feels “sick” Homeostasis is NOT being maintained

Lytic Cycle Step 3 – Replication Protein synthesis at ribosomes Use AA’s from host cell Nucleic acid synthesis Use host’s nucleotides Controlled by VIRAL DNA or RNA Uses host cell’s - nutrients, enzymes, and ATP

Lytic Cycle Step 4 – Assembly Step 5 – Release Put viruses together by inserting nucleic acid into protein coat Step 5 – Release Lysis – cell is destroyed by being broken open to release newly formed viruses (100’s or even 1000’s) Can now infect new cells => Cycle

Lytic Cycle - Summary Host gets “sick” right away DNA or RNA activated right away Short (usually days) Uses cell’s metabolism Examples: flu, cold, H1N1

Lysogenic Cycle Step 1 – Attachment and Entry Same as Steps 1 and 2 of Lytic Cycle Step 1 – Adsorption Attachment proteins “connect” by fitting the shape of plasma membrane receptor proteins; “tricking” the cell Step 2 – Entry Can be EITHER the whole virus OR the nucleic acid injected Virus is invading the host cell

Provirus – host DNA with viral DNA Host – bacteria (prokaryote) Lysogenic Cycle Step 2 – formation of provirus Viral DNA becomes incorporated into the host cell’s DNA Host does NOT feel “sick” Cell continues to function NORMALLY Homeostasis is NOT disrupted YET!!! DNA Provirus – host DNA with viral DNA Host – bacteria (prokaryote)

Lysogenic Cycle Step 3 – Mitosis/Cell division Host grows and functions NORMALLY Host undergoes mitosis Host unknowingly copies the viral DNA along with it’s own and passes them to daughter cells – infecting other cells Host STILL NOT “SICK”!!!

Lysogenic Cycle HOST is sick!!!!! Steps 4 through 6 – Viral DNA becomes “activated” and enters the Lytic Cycle Viral DNA takes over metabolism of host cell Viral genes and proteins are synthesized Viruses are assembled Lysis occurs and viruses are released HOST is sick!!!!!

Lysogenic Cycle Summary Host is able to function normally (for a while) – may not know they are infected Viral RNA will first be converted to DNA Provirus Uses cells metabolism to do mitosis Longer & more complicated MORE DANGEROUS Examples: HIV, cold sores