VIRUSES

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VIRUSES
Herpes
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Viruses

• are particles that are NOT ALIVE.

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Viruses reproduce ONLY inside a living CELL.
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The Structure Of a Virus

• Inner core of nucleic acid (This is the Viruses
  genetic material)
• Some contain DNA or RNA but never both.
• Surrounded by one or two protein coats called a
  capsid.

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EXAMPLES OF THE MANY DIFFERENT SHAPES OF VIRUSES

1. Tobacco Mosaic Virus
2. Polio Virus
3. Human Immunodeficiency Virus (HIV)
4. Bacteriophage T4

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E. Coli and the Bacteriophage

• What it looks like in real life

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T4 Bacteriophage
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• Every virus has a specially shaped device called
  an attachment protein that can only attach to a
  few kinds of cells.

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• Example of what bacteriophage (a type of virus)
  does to a cell
• Step 1 ATTACHMENT
• Step 2 ENTRY Bacteriophage injects nucelic acid
  into the bacterial cell
• Step 3 REPLICATION Hosts metabolic machinery
  makes viral nucleic acid and proteins

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• Step 4 ASSEMBLY New Virus particles are
  assembled
• Step 5 LYSIS AND RELEASE Host cell breaks open
  and releases new virus particles

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• Receptor proteins are proteins embedded in the
  cell membrane that bind to a signal molecule
  enabling it to respond to the signal molecule.
• Viruses are segments of nucleic acids contained
  in a protein coat. They are pathogens and
  reproduce by infecting cells and using the cell
  to make more viruses.
• Are viruses living? NO

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• Viruses have a protein coat and nucleic acid
  which are characteristics of living cells.
• Viruses also have characteristics of nonliving
  cells which are viruses do not respire, do not
  grow and CANNOT reproduce outside a living cell.

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• BECAUSE THEY DO NOT HAVE ALL THE PROPERTIES OF
  LIVING THINGS BIOLOGISTS DO NOT CONSIDER THEM
  LIVING.

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Viruses reproduce using 2 different cycles

• Lytic cycle Virus injects the cell with its
  genetic information, the information is
  integrated with the hosts DNA , the host is now
  replicating viral genes assembles the new
  viruses, and host cell is broken to release the
  new viruses. EX cold flu
• Lysogenic cycle_ Virus infects the cell,
  integrates its genetic information with the
  hosts DNA, the host divides normally, and then
  provirus may enter the lytic cycle. EX herpes
  HIV

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attaches
Bacterial
Lytic cycle
DNA
normally
viruses
Viruses
DNA
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HIV is a virus that causes AIDS.

• It has spikes on its surface that matches a
  receptor protein on macrophages, which is an
  immune system cell that engulfs pathogens, and
  infections fighting cells called lymphocytes.

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• AIDS is a disease in which an individual is
  unable to defend the body against infections that
  do not normally occur in healthy individuals.
• HIV infected people feel healthy for years and
  can spread it to others without knowing they are
  infected. HIV is NOT spread through casual
  contact but is transmitted in body fluids. This
  includes sexual contact, blood, and breast milk

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• Structure of HIV envelope composed of lipid
  bilayer from host cell, capsid and genetic
  material in the form of RNA.
• HIV attached to the cell at the receptors called
  CD4 which activates a co-receptor that in turn
  starts endocytosis.

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• This process occurs for years after infection an
  eventually mutates to a point it now recognizes a
  new cell surface receptor on T-Cells. HIV
  reproduces in the T cells and destroys them. This
  increases the amount of viral particles in the
  blood. The destruction of T cells blocks the
  bodys immune response and signals the onset of
  AIDS.

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Ebola
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Hepatitis
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Polio
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Rabies
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Smallpox

• 30 Fatal

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Vaccines

• Are used to PREVENT viral infections- What
  vaccines have you received in your lifetime?
• Viruses grown on chicken embryos are attenuated
  vaccines
• Another type of vaccine is made by heat killing
  the virus

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BACTERIA (MONERANS)

• Are the simplest of all living things and are
  prokaryotes (unicellular, Do NOT have a nucleus,
  and NO membrane bound organelles) Most are
  heterotrophs (Feed on other organisms).

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Characteristics of Bacteria

• Small
• Unicellular
• Circular DNA called a plasmid
• Can form endospores under harsh conditions

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2 types of reproduction

• Binary fission (Asexual) Chromosomes replicate
  and the cell divides
• Conjugation (Sexual) Exchange of genetic
  material through cell to cell contact

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2 Groups of Bacteria

• Archaebacteria (Ancient)
• Methanogens produce methane
• Thermophiles live in hot water
• Halophiles live in salty conditions (in the
  Dead Sea)
• Eubacteria

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Archaebacteria

• Methanogens- Produce methane
• Found in peat in marshes or hot springs
• Responsible for flatulence

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Archaebacteria

• Thermophiles- live in HOT water

                                        
   Thermophiles produce some of the bright colors
of Grand Prismatic Spring, Yellowstone National
Park
Pompei worms survive with symbiotic relationship
with thermophilic archaebacteria
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Archaebacteria

• Halophiles- Live in salty conditions (Dead Sea)

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STRUCTURE OF BACTERIA

• Capsule prevents bacteria from being easily
  engulfed by white blood cells
• Flagella Long thread-like (whip-like) tail that
  enables the bacteria to move
• Cell wall gives the cell shape and prevents
  osmosis from bursting the cell (Scientist use
  Gram-Staining to reveal the cell wall structure)

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STRUCTURE OF BACTERIA

• Chromosomes (nuclear material) not enclosed in a
  nucleus a single DNA molecule arranged as a
  CIRCULAR chromosome
• Plasma Membrane regulates what enters and leaves
  the cell

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SHAPES OF BACTERIA
Bacilli,or rod-shaped
Spirilli, or spiral shaped
Cocci, or round
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ANTIBIOTICS

• Are used to kill bacterial infections
• DO NOT WORK AGAINST VIRUSES

Pathogens

• Any living organisms or particle that can cause
  an infectious disease is called infectious agent,
  or pathogen

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Mutualism

• Symbiosis in which two of the species live
  together in such a way that both benefit from the
  relationship
• Ex. E. coli
• Escherichia coli