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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 Influenza HIV Smallpox Cowpox Polio Hepatitis Rabies Chicken pox Mono Cancer (HPV) Mono Shingles 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 & CELLS VIRUS 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