Welcome to Contemporary Biology

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Welcome to Contemporary Biology

• Your Host
• James Clack
• Office CORB101
• Phone [phone] or 800-414-8782x7266
• Email jclack_at_iupui.edu
• Office Hours by appointment
• Website http//iupucbio2.iupui.edu/n100

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Welcome to Contemporary Biology

• The Usual Disclaimers
• Remember that were squeezing 16 weeks into 8.
• Read assignments before class.
• Study early and often!
• Self-test -- ??s in the back of the chapter on
  the website.
• Use your common sense.
• Ask questions (as Ms. Frizzle says, Take
  chances, get messy, make mistakes!).

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What is Life?????

• Are there any signs of it in this room?

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Nanobes
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Shared Characteristics of Life
BUT viri, prions nanobes

• All living organisms
• are built of cells
• reproduce themselves using DNA
• grow and develop
• capture energy from their environment
• sense their environment and respond
• are organized
• evolve

retroviruses prions
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What is Life?????

• Another way of looking at it.

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Prions
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Prions

• Prions are pathogenic variants of proteins that
  are naturally produced in nerve cells and certain
  other cells. They have been implicated in a
  variety of transmissible spongiform
  encephalopathies, including sheep scrapie, mad
  cow disease, and human new-variant
  Creutzfeldt-Jakob disease.
• Normal, healthy prions are referred to as prion
  protein cellular (PrPc). In the illustration, the
  production of PrPc is shown from the nucleus (a).
  RNA that codes for PrPc is produced in the
  nucleus and exits via the nuclear pore. The RNA
  then passes along ribosomes attached to the rough
  endoplastic reticulum (rER). PrPc is formed in
  the rER and then progresses up through the Golgi
  complex. At the upper face of the Golgi, vesicles
  containing PrPc bud off and travel to the cell
  surface (b). There, they fuse with the cell
  membrane and so discharge their cargo (c). By
  this means, the cellular proteins come to sit on
  the exterior of the cell.
• In this illustration, PrPc particles encounter
  rogue prions, shown in purple (d). These are
  termed prion protein scrapie (PrPsc), for the
  prion disease of sheep. Such rogue prions seem to
  force normal proteins to change shape. Both types
  of proteinPrPc and its corresponding prionsare
  the same chemical, but in different shapes.
  Equivalent to the transmission of infection, such
  conformational shifting may take place at the
  cell surface or in caveolae (one is shown as a
  small invagination in the cell membrane). In such
  vesicles, residual PrPc may continue to be
  flipped by contact with rogue conformations for
  some time. Prions polymerize, finally appearing
  as purple fibrils (e).
• PrPsc is resistant to degradation by the enzymes
  contained in lysosomes (shown here floating
  nearby). Consequently, PrPsc accumulates in the
  cell. PrPsc vesicles may also travel to the Golgi
  and intercept PrPc that is being processed there.
  In this way, PrPc particles can be switched to
  the rogue form before they reach the surface of
  the cell. By such mechanisms, PrPc may be
  switched to PrPsc at various points in and on the
  cell.
• Prions may enter the brain along the axons of
  neurons (f). This probably happens by a
  retrograde flow of prion-filled vesicles (shown
  here as purple spheres ascending the axon).
  Another route of entry could be the blood,
  probably in immune cells. A lymphocyte is shown
  exiting the capillary at bottom left (g), where
  it could then contact the astrocyte (h).
  Astrocytes and other glial cells also support the
  production of prions.

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