Chapter 5: Homeostasis and Transport
when substances can cross the cell membrane w/o any input of energy by the cell
the movement of molecules from an area of higher concentration to lower conc.
the process when water molecules diffuse across a cell membrane from an area of higher to lower conc.
this process is used for molecules that cannot readily diffuese through cell memb. even when there is a concentration gradient across the memb.
-the movement of these kinds of molecules across the cell memb. are assisted by carrier proteins
Concentrations in and out of cell achieve equilibrium
-rate of water movement is the same
-net movement = 0 (Zero)
concentration of solute molecules *outside* the cell is higher than concentration of solute inside the cell
-net movement of H2O is out of cell
concentration of solute molecules *inside* the cell is higher than concentration of solute outside the cell
-net movement of H2O is into the cell
transport ions from higher to lower conc.
transport ions like...
organelles that remove water
the pressure that water molecules exert against the cell wall
the cells shrink away from the cell walls and turgor pressure is lost
-this the reason that plants wilt
the bursting of cells
when cells must move materials from an area of lower conc. to an area of higher conc. or 'up' their conc. gradient
-requires a cell to expend energy
Sodium Potassium Pump
this protein transports Na+ ions and K+ ions up their concentration gradients
-To function normally, some animal cells must have a higher conc. of Na+ ions outside the cell and a higher conc. of K+ ions inside the cell--> this pump maintains these conc. differences
the process when cells ingest external fluid, macromolecules, and large particles, including other cells
the process when a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the memb. to let the substance out of the cell