Cell Membrane Transport Flashcards
Allow cells to create and maintain different environments across a cell membrane
Selective permeability and regulated transport
membrane lipids allow unlimited passage of some substances but limited or no passage of other substances
selective permeability
movement from a region of [Higher concentration] to a region of [Lower concentration]
diffusion
The point where forward and backward reactions occur at the same time
Equilibrium
Equilibrium occurs when there is____
no movement, concentrations are equal
Types of Passive Transport
-Simple Diffusion
-Facilitated Diffusion
Type of Passive Transport:
-Used by small hydrophobic molecules (and water)
-molecules go directly through plasma membrane
Simple diffusion
Type of Passive Transport:
-Used by large hydrophilic molecules
-molecule goes through transport proteins
Facilitated diffusion
Transport Protein:
-Specific binding of solute
-Requires a confirmation change
-Hundreds or thousands transported per second
Carriers
Determines Direction of Transport:
-no energy added
-downhill
-[Higher] to [Lower]
-Driving force determined only by the direction of the electrochemical gradient
Passive Transport
Transport Protein:
-Hydrophilic pores; no specific binding to molecules
-allows rapid movement of ions and water
-millions or billions transported per second
Channels
“Electro”- charge distribution
“Chemical”- concentration gradient
Electrochemical gradient
Determines Direction of Transport:
-energy added
-uphill
-[Lower] to [Higher]
-Driving force is input energy
Active Transport
Passive diffusion of water across membrane
Osmosis
Osmosis:
Water molecules move from areas ____ to _____ concentrations
high to low
Osmosis:
Rapid movement of water occurs through “water channels” or ____
aquaporins
Osmosis:
Water is slowed down due to _____
polarity
Osmosis:
Water always moves towards ______ solute concentration
higher
Passive Water Movement:
-Solutions around cell has the same solute as inside cell
-equilibrium
isotonic
Passive Water Movement:
-solution around cell has a lower solute concentration outside than inside cell
-Net movement of h2o into the cell
hypotonic
Passive Water Movement:
-solution around the cell has a higher solute concentration than inside cell
-Net movement of h2o is out the cell
hypertonic
Channels maybe “gated” to control transport
-Ligand Gated
-Electrically Gated
-Mechanically Gated
facilitated diffusion
-Some transport proteins can move more than one substance at a time
-Can be both passive or active
Contransport
-uses cellular energy to transport substances against their gradients
-only carried
-NEVER channels
active transport
