CH 7

the boundary that separates the living cell from its surroundings

selectivley permeable

controlling passage across cellular membranes

are bound to the surface of the membrane

penetrate the hydrophobic core

Integral proteins that span the membrane.

ions and polar molecules do not cross the membrane easily

hydrocarbons can dissolve in the lipid bilayer and pass through the membrane rapidly

allow passage of hydrophilic substances across the membrane

bind to molecules and change shape to shuttle them across the membrane

the tendency for molecules to spread out evenly into the available space

-The diffusion of a substance across a biological membrane
- no energy is expended by the cell to make it happen
-from high to low concentration until evenly spaced

the diffusion of water across a selectively permeable membrane

the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides

when the concentration of a soluion is higher outside the cell than inside the cell

when the concentration of a solution is higer inside the cell than outside the cell

when the concentration is the same both inside and outside the cell

facilitate the transport of ions

open or close in response to a stimulus

low to high concentration

Passive Transport Aided by Proteins

passive transport

requires energy, from ATP hydrolysis, to move substances against their concentration gradient