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Exchange of substances across the cell membrane
Chater 3 pg 89-97
13
Anatomy
Undergraduate 1
02/10/2013

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Term
Diffusion
Definition
  • transport method
  • passive movement of substances down their concentration gradient from an area of high concentration to low
  • requires no energy
Term
Active transport
Definition
  • transport method
  • energy is required
  • substances move from a region of low concentration into a region of higher concentration
Term
Simple diffusion
Definition
  • Form of diffusion that does not involve membrane proteins
  • Other than carbon dioxide and oxygen, only lipids can cross the membrane by simple diffusion
Term
Facilitated diffusion
Definition
  • chemicals that are not lipid-soluble move down their concentration gradients by this
  • their transport is facilitated by the integral membrane proteins
Term
channels
Definition
  • watery tunnels through the cell membrane
  • have different shapes, which permit the passage of specific substances
Term
Carrier proteins
Definition
  • other substances, most importantly glucose, diffuse across the membrane through these
  • only allow passage of specific solutes
  • they change shape in order to enable transport
Term
Osmosis
Definition
  • the movement of water across a semipermeable membrane from the area of low solute osmolarity to an area of higher solute osmularity
  • changes the volume of a solution, and in confined spaces volume changes change the pressure
Term
Hypertonic
Definition
  • Have a greater solute concentration than the intracellular fluid, which means that the water concentration is higher inside the cell than outside
  • cells placed in a hypertonic solution will lose water and shrink, because water will exit the cell into the solution
Term
Isotonic
Definition
  • just right
  • the solute concentration is equivalent between the solution and the cell, and the cell volume will stay the same
  • cells placed in isotonic solutions neither gain nor lose water by osmosis
Term
Hypotonic
Definition
  • have lower solute concentration than the intracellular fluid, which means that water is in higher concentration ourside the cell than inside.
Term
Exocystosis
Definition
  • literally meaning, "out of a cell"
  • method by which a cell expels material in bulk
Term
Endocytosis
Definition
  • literally meaning, into a cell
  • begins as the cell membrane bulges inward
  • the membrane fuses and closes around a trapped substance, forming a vesicle in which the substance is enclosed in a sac of cell membrane
  • The vesicle then emerges with lysosome, whose enzymes digest the sac's contents. 
Term
Transcytosis
Definition
  • some cells combine endocytosis and exocytosis to move substances across the cell
  • endocytosis brings the substance into the cell, which is subsequently transferred to another vesicle for exocytosis. 
  • example: HIV, and herpes
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