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Viruses: Living or Not?

Viruses: Living or Not?. Virus . Biological particles that are NOT made of cells Viral particles are extremely small in size Don’t eat, respire or respond to their environment (No metabolism) Parasitic: they requires host Host is an organism that shelters and nourishes something

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Viruses: Living or Not?

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  1. Viruses: Living or Not?

  2. Virus Biological particles that are NOT made of cells • Viral particles are extremely small in size • Don’t eat, respire or respond to their environment (No metabolism) • Parasitic: they requires host • Host is an organism that shelters and nourishes something • Host provides the virus with all the materials needed to make copies of itself can NOT reproduce on its own • Therefore viruses are considered to be non- living

  3. What is a virus? TERMS you need to know • Pathogen: something that causes an illness • All viruses are pathogens • Not all pathogens are viruses – some bacteria can cause illnesses – you to become sick • Vector: how a virus gets into a host’s cell it wants to infect/use. Think of it’s the viruses key to get into the cell lock. • Viruses infect/attack specific cells (ex: HIV attacks immune cells, Flu virus infects throat, ear and nose cells) • Transmission: the passing of the virus from one organisms to another • Bacteriophage: a virus that attacks bacteria cells

  4. Characteristics of Viruses • Virus is a Latin word = virus • Not composed of cells • Contain-1 or 2 protein coats (Capsids) • Contain a genetic material – either RNA or DNA • DO NOT reproduce or grow • ONLY function in a living cell (Host) • Can not metabolize • Can adapt or respond to environment (that is how viruses get stronger or more harmful) • May have a viral Envelope • Not given Latin names

  5. Virus structure Made up of 5 different parts: 1. Capsid (Head): Protein coat made of protein – made up of proteins called capsomeres 2. Contains nucleic acid inside of the capsid: DNA or RNA • Influenza (FLU) virus has DNA • Retrovirus (HIV) has RNA 3. Envelope or Body: outer lipid layer and an inner protein layer surrounding the capsid. • Two different shapes 4. Projections or Tail: 6 tail fibers that help it bind to the host cell 5. binding proteins: allow the virus to attach to the host cell

  6. What makes a retrovirus different from all other organisms we study? • Retroviruses is a virus that contains an RNA core as it’s genetic material that replicates by transcribing it’s RNA into DNA. The DNA is then incorporated into the host’s genome • Retro means= reverse order or backwards • Retroviruses have an enzyme called reverse transcriptase which makes RNA transcribe DNA • Normal Cell: DNA RNA • Retrovirus RNA (template strand) DNA

  7. RETROVIRUSES • Most complicated • Genetic information flows in the reverse direction • Have the enzyme reverse transcriptase • Transcribes DNA from an RNA template • The newly made DNA than integrates as a provirus into the nucleus of the animal cell • The host’s RNA polymerase transcribes the virual DNA into RNA molecules.

  8. Example of viruses • smallpox • the common cold • chickenpox • influenza • shingles • herpes • polio • Rabies, • Ebola • AIDS

  9. Different Types of Viruses • ADENOVIRUS • Respiratory infections; colds

  10. Polio

  11. Influenza Virus • Virus that causes the flu

  12. Small Pox

  13. TMV

  14. Viruses are classified by: • type of host cell • presence of DNA or RNA (retroviruses) • shape: Binal Polyhedral Filo

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