Cell Function Notes Sub

Cell Function NotesCell Function Notes4/2/094/2/09

Cells: Movement of SubstancesCells: Movement of Substances

cell membrane is made up of cell membrane is made up of phospholipid phospholipid bilayerbilayer with embedded proteins with embedded proteins


model for this is called model for this is called fluid mosaic modelfluid mosaic model it is a phospholipid bilayer with embedded it is a phospholipid bilayer with embedded

proteinsproteins


receptor proteins on surfaces recognize and receptor proteins on surfaces recognize and accept other substancesaccept other substances

carrier proteins extend through the membrane carrier proteins extend through the membrane and actively move substances throughand actively move substances through


ability to move substances in and out of ability to move substances in and out of cell is directly related to available surface cell is directly related to available surface areaarea


function of membranesfunction of membranesmaintain integrity of cellmaintain integrity of cellcontrol permeabilitycontrol permeability

permeablepermeable – all molecules pass through – all molecules pass throughimpermeableimpermeable – no molecules pass through – no molecules pass throughdifferentially (selectively) permeabledifferentially (selectively) permeable – only some – only some

molecules can passmolecules can pass


concentration gradientsconcentration gradients the concentration at various points between the concentration at various points between

the high and low forms a gradientthe high and low forms a gradientmoving high to low is “down” or “with” the moving high to low is “down” or “with” the

gradientgradientmoving low to high is “up” or “against” the moving low to high is “up” or “against” the

gradientgradient


active transportactive transport requires energy by cell to move molecules requires energy by cell to move molecules

against (up) the concentration gradientagainst (up) the concentration gradientphysiological pumps (NaK)physiological pumps (NaK)endocytosis and exocytosisendocytosis and exocytosis


passive transportpassive transport requires no energy by the cell, molecules requires no energy by the cell, molecules

move down the concentration gradientmove down the concentration gradient


passive transportpassive transportdiffusiondiffusion

movement of molecules from an area of high movement of molecules from an area of high concentration to an area of low concentrationconcentration to an area of low concentration

examplesexamples smell of popcornsmell of popcorn drop of food coloring in waterdrop of food coloring in water


passive transportpassive transportosmosisosmosis

movement of water through membranesmovement of water through membranesto determine if the water will travel into or out of to determine if the water will travel into or out of

the cell, you need to compare the solute the cell, you need to compare the solute concentration or concentration or tonicitytonicity

solutesolute – the substance being dissolved – the substance being dissolved solutionsolution – the liquid – the liquid


passive transportpassive transport tonicity is the relative concentration of solutestonicity is the relative concentration of solutes

isotonicisotonic: solute concentrations are equal in cell : solute concentrations are equal in cell and solutionand solution

molecules will move into and out of cellmolecules will move into and out of cell



hypotonichypotonic: has less solutes: has less solutes surrounding fluid has LOWER conc. than cellsurrounding fluid has LOWER conc. than cell a cell in a hypotonic solution will expand as water flows a cell in a hypotonic solution will expand as water flows

into the cellinto the cell plant cell – plant cell – turgor pressureturgor pressure animal cell – animal cell – cytolysiscytolysis (bursts) (bursts)



hypertonichypertonic: has more solutes: has more solutes surrounding fluid has HIGHER conc. than cellsurrounding fluid has HIGHER conc. than cell a cell in a hypertonic solution will shrink as water flows a cell in a hypertonic solution will shrink as water flows

out of cellout of cell in both plants and animal cells this is called in both plants and animal cells this is called

plasmylosisplasmylosis This is why plants wilt!This is why plants wilt!

EXAMPLEEXAMPLE

Plant CellsPlant Cellsguard cells control size of stomatesguard cells control size of stomates

stomate is an opening on bottom surface of leafstomate is an opening on bottom surface of leafwhen guard cells expand, stomate closeswhen guard cells expand, stomate closeswhen guard cells shrink, stomate openswhen guard cells shrink, stomate opens

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