Membrane Notes Review

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Membrane Notes Review
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Structure of the Plasma Membrane

• Lipid bilayer two sheets of lipids
  (phospholipids).
• Found around the cell, the nucleus, vacuoles,
  mitochondria, and chloroplasts.
• Embedded with proteins and strengthened with
  cholesterol molecules.

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Membrane Proteins

• 1. Determine what particles can pass through the
  membrane.
• 2. Serve as enzymes (may speed reactions).
• 3. Act as markers that are recognized by
  chemicals and molecules from the inside and the
  outside of the cell (the immune system).

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Types of Transportation
Active
Passive
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Three Forms of Transport Across the Membrane
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Passive Transport

• Simple Diffusion
• Doesnt require energy
• Moves high to low concentration
• Example Oxygen or water diffusing into a cell
  and carbon dioxide diffusing out.

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Cell Concentrations

• Hypertonic solutions more dissolved solute.
• Hypotonic solutions less dissolved solute.
• Isotonic solutions the same dissolved solute.
• Solventdoes the dissolving
• Solutesolid(usually) which is dissolved

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There are three types of solutions       (1)
Hypotonic - a solution which is more dilute
(i.e., less solutes) than the cytosol. The cell
gains water and swells.                          
            (2) Hypertonic - a solution which is
more concentrated (i.e., more solutes) than the
cytosol. The cells loses water and
shrinks.   (3)  Isotonic - a solution which has
the same concentration of solutes as the cytosol.
The cell neither gains nor loses water and
remains unchanged.
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TONICITY the relative amount of solute
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HYPERTONIC Concentration outside cell is
____________________ inside cell More water
leaves cell than enters so cell ____________
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• HYPOTONIC Concentration outside cell is
  ________________ inside the cellMore water
  enters than leaves cell so cellwill
  ___________________

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ISOTONIC Concentration outside cell
__________ concentration inside cell Water
entering water leavingso cell
_____________________
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Osmosis

• Diffusion of water across a selectively permeable
  membrane.
• Occurs until water is balanced on both sides of
  the membrane.

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Passive Transport

• Facilitated diffusion
• Doesnt require energy
• Uses transport proteins to move high to low
  concentration
• Examples Glucose or amino acids moving from
  blood into a cell.

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Active Transport

• Requires energy or ATP
• Moves materials from LOW to HIGH concentration
• AGAINST concentration gradient

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Sodium-Potassium Pump
3 Na pumped in for every 2 K pumped out
creates a membrane potential
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Endocytosis Phagocytosis
Used to engulf large particles such as food,
bacteria, etc. into vesicles
Called Cell Eating
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Exocytosis The opposite of endocytosis is
exocytosis. Large molecules that are manufactured
in the cell are released through the cell
membrane.
Inside Cell
Cell environment
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Pinocytosis
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.