Transcript Cellular Transport Across the Membrane

CELLULAR TRANSPORT
ACROSS THE MEMBRANE
Let’s Remember the Cell Membrane
Sometimes a concentration gradient is created
around the cell membrane.
A concentration
gradient is the
difference in the
concentration of a
substance from
one location to
another
There are two types of transport across
the cell membrane
Passive Transport:
Moves molecules
from an area of high
concentration to low
concentration.
Active Transport:
Molecules move from
an area of low
concentration to high
concentration
Passive Transport is the movement of molecules across a
cell membrane without energy input.
It is the movement of molecules from an area of high
concentration to low concentration. It is also known as
DIFFUSION.
Molecules will continue to move until they have reached
equilibrium, or a balance on both sides of the
membrane.
Molecules that diffuse across the cells
membrane are small and nonpolar
Osmosis is a form of diffusion
Osmosis is
the diffusion
Of water
Cells can have many relationships with the solutions
around them.
Isotonic Solution
In a hypertonic solution, water will exit
the cell causing it to shrivel.
In a hypotonic solution, water will enter the
cell and cause it to swell.
Facilitated Diffusion
Facilitated
diffusion is the
diffusion of
molecules into a
cell using
membrane
proteins.
Remember: Active transport moves molecules from an area
of low concentration to high using chemical energy
The different types of active transport are:
Endocytosis
 Exocytosis

Endocytosis is the process of taking liquids or fairly
large molecules into a cell by engulfing them in the
membrane.
1.
2.
3.
4.
Cells make a pocket around a substance
The pocket will break off inside of the cell and form a
vesicle
The vesicle will fuse with a lysosome and be digested.
The substance is released into the cell.
Phagocytosis is a form of endocytosis
In phagocytosis, large molecules are
engulfed into the cell.
Exocytosis is the opposite of endocytosis
1.
2.
Substances in the cell
are enclosed in
vesicles.
Vesicles will fuse with
the cell membrane
and release it’s
contents on the
outside of the cell.