VIRUSES - Small non-cellular particles - Seen only with an electron microscope - Classified according to their shape - Classified according to their molecular.

VIRUSES

- Small non-cellular particles- Seen only with an electron microscope- Classified according to their shape- Classified according to their molecular structure

COMMON VIRAL NAMES:

• Herpes Chicken pox• Influenza Mono• HIV Cancer (HPV)• Smallpox Mono• Cowpox Shingles• Polio• Hepatitis• Rabies

IN ORDER TO STUDY VIRUSES…. WE MUST:

• Isolate it from its host• Hosts could be:• animals• plants• bacteria• cells

• Inside the host it produces new viruses

• All viruses have one type of nucleic acid: DNA or RNA

• Most viruses are haploid

• Viral nucleic acid is covered by a protein coat (called a CAPSID)

SHAPES OF VIRUSES

• Two shapes: cubic symmetry & helical symmetry

• CUBIC

• HELICAL

CHEMISTRY OF VIRUSES

• Most viruses have no enzymes• Cannot make protein on its own• Require the protein synthesis machinery of

its host cell• Cannot make their own ATP• Act as intracellular parasites• Replicate themselves by making copies if

their parts which are assembled using host building block materials

• Viruses do not grow bigger then divide

• They dissemble, make new parts, they assemble parts identical to the parent virus

• All of this takes place in the host cell

• Are viruses living ?

DIFFERENCES BETWEEN VIRUSES & CELLSVIRUS CELLS

• DNA or RNA, in various forms as the genetic info.

• Few proteins, mainly as a cover for nucleic acid

• Few or no enzymes• Cannot make ATP• Intracellular synthesis

then assembly

• Always both DNA & RNA as genetic info.

• Hundreds of proteins in various structures

• All have sugars & lipids

• Hundreds of enzymes• Makes ATP• Division by mitosis or

fission

VIRAL REPLICATION

• ATTACHMENT & entrance: virus chemically recognized its host & attach to it.

• Whole virus or only its DNA or RNA enters its host cell

• SYNTHESIS of protein and nucleic acid

• Molecular info. Inside the virus directs the host cell to replicate viral proteins

• ASSEMBLY of the units:• The viral nucleic acids, enzymes, and

proteins are brought together and assembled into new viruses

• RELEASE of new virus particles:• Newly formed viruses released from

infected cell and the host cell dies

LYTIC & LYSOGENIC CYCLES OF VIRUSES

• LYTIC CYCLE can be completed in as little as 25-45 minutes

• 300 new viruses can be produced

• Lysis = destruction or bursting open of host cell releasing new viruses

• BACTERIOPHAGES (viruses that infect bacteria) cause cell lysis (cell death)

• LYSOGENIC CYCLE = replicated viruses can lay dormant inside their host

• Dormant virus can be activated by stress, temperature increases above 37 degrees, lack of certain food nutrients.

VACCINES• VACCINES are

solutions that are prepared from viral components or inactivated viruses

• Body reacts to vaccine as if it were a real virus and produces antibodies

I HAVE LIKELY BEEN VACCINATED AGAINST:

• Chicken pox• Polio• Measles• Mumps• Rubella• Influenza• HPV• hepatitis

Your Dog & Cat Against….RABIES