Cell Membrane

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Cell Membrane

• Cell Membrane is very complex. Its made of
  phospholipid bilayer with proteins throughout.

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• some proteins extend all the way through
  (Integral Proteins) and some stay on surface
  (Peripheral Proteins)
• integral proteins form channels or carriers
• peripheral act as recognition sites

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Phospholipid Bilayer

• Hydrophilic water loving (phophate head)
• Hydrophobic water fearing (lipid tails)

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Fluid Mosaic Model

• lipids and proteins of cell membrane are
  always in motion, drifting around, hence name
  Fluid Mosaic Model of membrane structure

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Fluid Mosaic Model

• Cell membrane acts as a dam or pump for
  water-soluble molecules that cant pass freely
  through.Interactive Educational Animations
•  
• Water diffuses across the membrane, called
  osmosis. This regulation of water across the
  cell membrane is vital to homeostasis.

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DIFFUSION

• All particles are moving and therefore have
  energy of motion called kinetic energy, whether
  living or nonliving.
• When there is a difference in concentration
  across a space this is called a concentration
  gradient.

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DIFFUSION

• The movement from higher concentration to lower
  concentration. This happens b/c of kinetic
  energy.
• Diffusion

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Rate of diffusion

1. Concentration- more concentrated diffuses faster.
   
2. Pressure- increasing pressure will increase
   kinetic energy and diffusion.
3. Temperature- higher temps increase kinetic energy
   and also diffusion.

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Dynamic Equilibrium

• Once diffusion has occurred and there are equal
  concentrations, there is still continuous
  movement (kinetic energy), however there is no
  more concentration change

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Osmosis

• Diffusion with water across a semipermeable
  membrane.
• Very vital to biology.
• Osmosis animation

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HYPERTONIC SOLUTION

• The concentration of solute molecules outside the
  cell is higher than conc. inside the cell. H2O
  diffuses out of the cell to equilibrium.
• -Cell in hypertonic solution shrink. Plant cells
  detach from cell wall (PLASMOLYSIS), plants wilt.

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HYPOTONIC SOLUTION

• The conc. of solute molecules outside the cell is
  lower than conc. inside the cell cytosol. H2O
  diffuses into the cell to equilibrium.
• -Cell in hypotonic solution swell. Animal cells
  in this environ. will burst (CYTOLYSIS). Plant
  cells have cell wall and just become rigid.

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ISOTONIC SOLUTION

• conc. of solutes is equal in and out of cell.
• Cells must be able to attempt to adapt to these
  environments. Must actively transport water and
  materials into and out of cell.

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Passive Transport- no energy required.

• 1. Diffusion, Osmosis- most molecules can not
  enter or exit cell this way. (oxygen, H2O)

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Passive Transport

• 2. Facilitated Diffusion- no energy required.
  Molecules are diffused into and out of cell with
  the help of molecule-specific carrier proteins
  and ion channels (protein tunnel). (Glucose,
  Na, K)

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Active Transport- requires energy (ATP)- usually
against the conc. gradient- uses carrier
proteins.

• 1. Sodium-Potassium Pumps- animal cells, pump Na
  out and K in.

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Active Transport

• 2. Plant roots- nutrients inside roots more conc.
  than out. Pumped in.

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Active Transport

• 3. Bulk Transport- large molecules, food packaged
  in membrane-bound sacs (vesicles) to move across
  membrane.
• a. Endocytosis- cell membrane folds in,
  surrounds molecule, becomes sac

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Active Transport

• b. Pinocytosis- cell drinking brings liquid in
• c. Phagocytosis- cell eating brings food in
  lysosomes digest White Blood Cells

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Active Transport

• d. Exocytosis- vesicles made by golgi or ER and
  merge w/ cell membrane to exit material from
  cell.

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Organization of Multicellular Organisms

1. Cell- smallest unit of life capable of all
   functions of life
2. Tissue- group of cells, perform a specific
   function

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Organization of Multicellular Organisms

• 3. Organ- several different types of tissue
  function together for a specific purpose

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Organization of Multicellular Organisms

• 4. Organ System- several organs working together
  to perform a function

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Organization of Multicellular Organisms

• 5. Organism- all organ systems working together