Communication and Multicellular Organisms

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Communication and Multicellular Organisms
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Multicellular Organisms

• ? Made of many cells
• Ex Plant and animals

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Fact

• Cells in multicellular organisms must be able
  to communicate to
• Coordinate their behavior within the organism
• Adjust their metabolism
• Grow and divide at the proper time

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Receptor proteins

• Found on surface and interior of the cell
• Send information from environment to cell
• Use hormones as messengers- chemical signals
• Ex Glucagons- Protein hormone made in the
  pancreas
• Binds with receptor proteins in liver cells to
  release sugar

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• Ex Hydrophobic hormones (water-hating)
• Unlike protein hormones because they are able to
  pass through lipid bilayer
• Inside the cell they bind with receptor proteins

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• Examples
• Thyroxin Hormone that controls metabolic rate
• Estrogen Hormones responsible for sexual
  characteristics
• Testosterone Hormones responsible for
  sexual characteristics

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Voltage Sensitive Channels

• -found in neurons nerves
• When ions are balanced there is an equal charge
  inside and outside of cell CLOSED CHANNEL

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Nerve Cell

• Specialized cells that carry info from one cell
  to the next
• When ions are not balanced OPENED CHANNEL
• Voltage Sensitive Channels allows signals to
  travel quickly through the nervous system (100
  m/s) meter/second

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Cell Surface Marker

• Cell surface markers Identify owner of cells
• 1) allows immune system to recognize
  uninvited guests - bacteria/viruses
• 2) helps during early growth of a cell to
  define the cells role
• (Cell surface markers only match in identical
  twins)

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• Organ donors If the cell surface markers do not
  match, the body will reject the transplanted
  organ.

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Movement of Substances Into and Out of Cells

• (Water molecules, food particles, and ions)

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Diffusion

• Mixing of (2) substances by random motion of
  molecules
• These molecules move from a region of high
  to a region of low ( means
  concentrations)
• Diffusion stops when the (2) substances are
  evenly dispersed.

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• Water enters and leaves living cells by diffusing
  across cell membranes. (Small water molecules
  can move freely through the tiny gaps in the
  lipid bilayer.) This enables cells to absorb
  water.

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Osmosis

• the diffusion of water across a membrane (cell
  membrane)
• Water molecules move from an area of ? to an
  area of ?
• Water moves into a cell ? causes cell to swell
  osmotic pressure

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• 3. If osmotic pressure is too high the cell
  could burst
• 4. In plant cells, the cell wall prevents the
  cell from bursting
• 5. In animal cells there exists a pump that
  moves extra water out to prevent bursting
• 6. Homeostasis- The balance in fluids
  inside and outside the cells

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Channels and Pumps Provide Selective Transport

• Molecules like sugars and proteins are
• too big to pass through the cell membrane
• polar and cannot pass by nonpolar region
• so they use channels and pumps made of
  proteins

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Selective Transport

• Enables certain substances to pass in or out of
  the cell which allows the cell to control what
  substances enter or leave the cell

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Two types of selective transport
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Facilitated Diffusion
Facilitated means to help or assist.

• As long as the substance can fit into the
  protein channel,
• the substance can move in or out
• Assists the diffusion of substances
• Substances move because of differences in
  inside and
• outside the cell.
• No energy is used
• Ex Sugar

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Active transport

• Operation of pumps to move substances like sugars
  and amino acids in one direction
• (like a turnstile)
• Energy is needed

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Two types
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Sodium-Potassium pump

• a. Sodium ions move out (300 Na/sec)
• b. Potassium ions move in
• c. Important to keep nerve cells functioning
• (1/3 of al the E spent by the bodys
  cells)
• d. Helps transport sugars and amino acids into
• cells

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Proton pump-

• Moves protons across the cell membrane
• Needs chemical or light E to function

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Defective Channel Proteins can be lethal

• A change in protein structure can alter/impair
  function and threaten the cells normal activity
• Read pg 71
• What is cystic fibrosis?
• What causes CF?

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Moving Large Particles

• Endocytosis the process of bringing large
  particles into the cell

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• Exocytosis the process of moving particles out
  of the cell
• This process is endocytosis backwards.