Transcript Chapter2, Sect 2 notes

LS. 3
The Cell In Its
Environment
The cell membrane is selectively
permeable, which means that
some substances can pass
through it.
Substances that can move into
and out of a cell do so by one of
two methods:
Passive transport or active
transport
Passive Transport is the
movement of materials
through the cell
membrane without using
energy.
•Diffusion – the process by which
molecules tend to move from an
area of high concentration to an
area of lower concentration. (No
energy required.)
Osmosis – the diffusion of water
molecules through a selectively
permeable membrane. Osmosis
is important because cells
cannot function properly without
water. (No energy required.)
Facilitated Diffusion is a process in
which proteins in the cell
membrane form channels through
which molecules such as sugar
pass.
Facilitated Diffusion uses no
cellular energy and is another form
of passive transport.
•Osmosis and Diffusion are both
types of passive transport.
•Active transport – the movement
of materials through a membrane
using energy. (Low concentration
to high concentration)
The main difference between
passive and active transport is that
active requires the cell to use
energy while passive does not.
Two methods of active transport
are:
Endocytosis and Exocytosis