Getting In & Out of a Cell Osmosis & Diffusion Getting In & Out of a Cell Osmosis & Diffusion.
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Transcript of Getting In & Out of a Cell Osmosis & Diffusion Getting In & Out of a Cell Osmosis & Diffusion.
Getting In & Out of a Cell
Osmosis & Diffusion
Cell Membrane
• Remember: The Cell Membrane is SEMI-PERMEABLE– It doesn’t let
EVERYTHING inside the cell
• Cells do this to maintain homeostasis– Stable internal
environment
PASSIVE TRANSPORT
• Substances that cross the cell membrane without taking energy from the cell
DIFFUSION• The movement of
molecules from an area of high concentration to low concentration– Concentration
gradient = difference in concentration!
• Eventually this leads to equilibrium– Equal concentration
throughout space
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Sugar Molecules
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Sugar Molecules
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Sugar Molecules
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Sugar Molecules
OSMOSIS
• Process of WATER diffusing across a cell membrane from an area of higher concentration to an area of lower concentration
Directions of Osmosis
• The net direction of osmosis depends on the concentration of solutes outside & inside the cell– Hypotonic– Hypertonic– Isotonic
HYPOTONIC
• Concentration of molecules are lower on OUTSIDE of cell
• Water diffuses INTO the cell
HYPERTONIC
• Concentration of molecules are lower on the INSIDE of the cell
• WATER diffuses OUT of the cell
ISOTONIC
• Concentration of molecules is equal inside & outside the cell– At equilibrium
• Water diffuses equally into and out of the cell– No NET movement
of water
Examples
ION CHANNELS – FACILITATED DIFFUSION
• Membrane proteins that allow ions to enter the cell
• Ions must go through channels because they can’t dissolve through lipid bilayer
ACTIVE TRANSPORT
• Movement of materials against the concentration gradient
• Requires energy
• Called “pumps”
ENDOCYTOSIS
• Process of cells ingesting external fluid, macromolecules, other cells, etc.
• Cells do this for substances that are too BIG to pass through the cell membrane
ENDOCYTOSIS CONT…
• External materials are enclosed in a membrane-bound organelle called a VESICLE
• These can fuse with lysosomes to be digested
PINOCYTOSIS & PHAGOCYTOSIS
• Pinocytosis– Solutes or fluid
• Phagocytosis– Large particles or
whole cells
EXOCYTOSIS
• Vesicles in the cell fuse with the cell membrane and release the contents
EXAMPLES