Moving Cellular
Material
Chapter 2 Lesson 3
unit membrane
• a thin structure composed
of proteins and lipids
• type of membrane found
around all cells
• around many of the
structures inside cells
• the outer boundary of a
cell
Important Property of
Membranes
selectively permeable:
certain molecules go
through them and other
molecules do not
Selectively Permeable
Not all membranes are
permeable to the same
molecules.
However water, oxygen,
and carbon dioxide are
small and easily passes
through most membranes.
How does a substance
pass through a unit
membrane?
Passive Transport
Active Transport
Facilitated Diffusion
PASSIVE TRANSPORT
the passage of
substances across a
membrane without
the use of energy
PASSIVE TRANSPORT
 Small molecules, such as oxygen
and carbon dioxide, pass through
membranes via passive transport.
 Passive transport depends on the
amount of substance on each side
of a membrane.
This is the main way.
two main forms of
passive transport
Diffusion
Osmosis
diffusion
the movement of molecules
from an area of higher
concentration to an area
of lower concentration
diffusion
from Latin diffusionem, means “scatter, pour out”
diffusion
diffusion can be
speeded up by such
things as
heat,movement, and
pressure
Diffusion
Diffusion continues until the concentration of a
substance is the same on both sides of the
membrane. The substance is then in equilibrium.
osmosis
the diffusion of
water through a
membrane
osmosis
Semipermeable cell membranes allow
water to pass through them until
equilibrium occurs.
Facilitated Diffusion
• Facilitated diffusion occurs when
molecules pass through a cell membrane
using special proteins called transport
proteins.
• Carrier proteins are transport proteins that
carry large molecules through the cell
membrane.
• Channel proteins are transport proteins that
form pores through the cell membrane.
Facilitated Diffusion
*Is a type of passive transport
• Doesn’t require energy
• Uses transport proteins to move
molecules from high to low
concentration
Facilitated Diffusion- is the movement of
larger molecules like glucose through the
cell membrane  larger molecules must be
“helped”
Examples: Glucose or amino acids moving
from blood into a cell.
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Facilitated Diffusion
ACTIVE TRANSPORT
the passage of particles
through a membrane; requires
the use of cellular energy
(sometimes because of the
size of the molecule being
so large, or going against
gradient)
Active Transport
Requires Energy.
ATP (form of energy
made by
mitochondria).
Moves against the
concentration
gradient.
High
This is
going to
be hard
work!!
low
Sodium Potassium Pump
What I need to know
Active transport goes
AGAINST the
concentration
gradient
Low solute
concentration to high
solute concentration
The cell uses energy
(ATP) to actively
transport Na+ out of
the cell and K+ into the
cell against the
concentration gradient
Sodium Potassium Pump
• Endocytosis and Exocytosis is the mechanism by which
very large molecules (such as food and wastes) get into
and out of the cell
• **ENERGY IS REQUIRED
Food is moved into the
cell by Endocytosis
Wastes are moved out
of the cell by
Exocytosis
Endocytosis
Transporting material into
a cell by the in folding
of a membrane.
Think endoThink enter
To take inside of the cell
2 Types of Endocytosis
Phagocytosis- Solid
particles are ingested
into the cell.
Pinocytosis – liquids
and very small
molecules are taken
into the cell.
Endocytosis
Exocytosis
Moves materials
out of the cell
Think exoThink exit
Moving the “Big Stuff”
Exocytosismoving
things out.
Molecules are moved out of the cell by vesicles that fuse with the
plasma membrane.
This is how many hormones are secreted and how nerve cells
communicate with one another.
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