Download Biology Notes: Viruses

Name: _________________________________________________ Date: _______________ Period: ________ Biology Notes: Viruses What is a virus? • Virus: A biological particle composed of ______________________________ and _______________. • Intracellular Parasites: organism that _______________ “live” inside a host Are viruses alive? • YES • NO – Reproduce – Not made of cells or organelles – Have nucleic acid – Can’t reproduce on own – Adapt to surroundings – Don’t metabolize energy – Have organization – Don’t perform cellular processes Virus Parts • All Have: – 1) Capsid: coat of ________________ that surrounds ________________________________. – 2) Nucleic Acid: _________________ or ________________ • Some Have: – Tail Fibers: Used for _____________________ (not legs) • Shape & size varies Viral Replication • Bacteriophages (viruses that attack bacteria) are often studied • Replication is similar with many animal viruses • Two “life” cycles: Lytic & Lysogenic The Lytic Cycle st
• 1 Step: Attachment – Virus lands on cell membrane – Virus attaches to a cell _______________ – Virus acts as ______________; receptor acts as ______________ – No attachment = No ______________ nd
• 2 Step: Entry – Virus enzyme ________________ cell membrane – Genetic material (DNA or RNA) _______________ host cell rd
• 3 Step: Replication – Virus DNA/RNA uses ribosomes to make ________________ proteins – Virus proteins created by _______________________________________________________________ th
• 4 Step: Assembly • ________________ virus proteins are assembled in the cell’s ________________ th
• 5 Step: Release – Virus enzyme causes cell membrane _________________ (burst) – Viruses are ________________ to find new ________________ – Cycle repeats Lysogenic Cycle: st
• 1 step: Attachment = Same as _________________ cycle - Virus lands on cell membrane. Virus attaches to a cell _______________ nd
• 2 Step: Entry = Same as _________________ cycle - Virus enzyme ________________ cell membrane Genetic material (DNA or RNA) _______________ host cell rd
• 3 step: Replication – _________________ created – ______________________ combines with cell DNA = PROVIRUS! – Infected cell divides by _______________ and copies the ________________ – Each new cell will contain the ________________ • 4th Step: Assembly: Same except, many new _______________ are assembled in _______________cells. • 5th Step: Release: Same except, many cells ________________, releasing many more viruses. ReView (at the end of the PowerPoint you should be able to answer these questions) 1. True or False: All viruses have a capsid, nucleic acid, and tail fibers. 2. List 3 reasons why viruses may be living? Nonliving? 3. What is the virus capsid made from? 4. What type of organism do phages infect? 5. In order list the stages of the lytic/lysogenic cycles. 6. In which stage… - Does the host cell explode?________________ - Are virus proteins built to make new viruses? ______________________________________ - Is a provirus created? _____________________ - Does a virus connect with the host cell’s receptors? ______________________________ 7. Which two objects make up a provirus? 8. Which virus “life” cycle is considered the most harmful? Why? 9. Place the following steps of the lytic cycle in order (#1 = First).