Cell Structure and Function
Transcript Cell Structure and Function
A water solution that contains
nutrients, waste products, gases,
salts, & other substances surrounds
External environment of the cell.
The Plasma membrane separates
the cell’s internal & external
Selectively permeable – small
molecules can pass through freely,
while larger molecules cannot.
Molecules are in constant motion due to
their kinetic energy.
Molecules move randomly.
Random motion tends to create uniform
Net movement of molecules toward the area
where they are scarce – down the
Diffusion allows O2, CO2, & nonpolar
liquids to cross plasma membrane.
from region of
to region of
are small enough
to pass through
Osmosis is the
diffusion of water
across the plasma
membrane of a cell
from a region of
concentration to a
region of lower
Solutes are molecules dissolved in a solution.
Tonicity – the relative concentration of solute
(particles), and therefore also of solvent (water)
outside the cell compared to inside the cell.
Hypertonic – solution with higher solute
concentration than inside the cell.
Hypotonic – solution with lower solute concentration.
Isotonic – solution with solute concentration equal to
that inside the cell.
water into a cell
Can cause cell to
swell and burst.
Cell walls protect
plant cells from