Transcript The Cell Membrane

Cell Transport
It’s all about in and out.
Passive Transport

When a cell uses no energy to move particles
across a membrane.
Plasma
membrane
Concentration
gradient
Facilitated diffusion

Passive transport of materials across the
membrane using transport proteins.
Channel
proteins
Plasma
membrane
Concentration
gradient
Facilitated diffusion

Channel proteins form channels that allow specific
molecules to flow through.

Movement is with the concentration gradient, and
requires no energy input from the cell.
Channel
proteins
Plasma
membrane
Concentration
gradient
Facilitated diffusion


Carrier proteins change shape to allow a substance to
pass through the plasma membrane.
Movement is with the concentration gradient and
requires no energy.
Carrier proteins
Concentration
gradient
Plasma
membrane
Step 1
Step 2
Facilitated Diffusion
Facilitated Diffusion Transport
Proteins
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.

Click image to view movie.
Active Transport

Movement of materials through a membrane
against a concentration gradient; requires
energy from the cell.
Carrier
proteins
Plasma
membrane
Concentration
gradient
Cellular
energy
Step 1
Step 2
How active transport occurs
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.

Click image to view movie.
How active transport occurs

A carrier protein binds with a particle.
 Each type of carrier protein has a shape that
fits a specific molecule or ion.
Carrier
proteins
Plasma
membrane
Concentration
gradient
Cellular
energy
Step 1
Step 2
How active transport occurs

Chemical energy changes the shape of the
carrier protein
 The particle is released on the other side of the
membrane.
Carrier
proteins
Plasma
membrane
Concentration
gradient
Cellular
energy
Step 1
Step 2
How active transport occurs
Once the particle is released, the protein’s
original shape is restored.
 Allows particle movement into or out of a cell
against a concentration gradient.

Carrier
proteins
Plasma
membrane
Concentration
gradient
Cellular
energy
Step 1
Step 2
Membrane Potentials

Active transport can
store energy by
creating a difference
in concentration of
particles on each
side.
– Kind of like a battery.
Membrane Potentials

Uses:
– Transporting other
things
– Making bonds – like
during
photosynthesis or cell
respiration
– Carrying signals –
like in nerves
Antiporter
Symporter
Transport of Large Particles

Endocytosis is a process by which a cell
surrounds and takes in material from its
environment.
Nucleus
Wastes
Digestion
Endocytosis
Exocytosis
Transport of Large Particles

The material is engulfed and enclosed by a
portion of the cell’s plasma membrane.
Nucleus
Wastes
Digestion
Endocytosis
Exocytosis
Transport of Large Particles

The resulting vacuole with its contents moves
to the inside of the cell.
Nucleus
Wastes
Digestion
Endocytosis
Exocytosis
Transport of Large Particles

Exocytosis is the expulsion or secretion of
materials from a cell.
Nucleus
Wastes
Digestion
Endocytosis
Exocytosis
Amoeba Doing Endocytosis (Phagocytosis)
Amoeba Doing Endocytosis (Phagocytosis)
Amoeba Doing Endocytosis (Phagocytosis)
Amoeba Doing Endocytosis (Phagocytosis)
Amoeba Doing Endocytosis (Phagocytosis)
Amoeba Doing Endocytosis (Phagocytosis)
Amoeba Doing Endocytosis (Phagocytosis)
Endocytosis

http://biology.semo.edu/courses/bi190/
The formation of
a membrane
bound vacuole
from cell
membrane to
enclose a particle
and bring it inside
the cell.
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
Click to Show Movie
Exocytosis

http://www.biology.washington.edu/bsa/IonTransport/exocytosis.html
The process by
which membrane
material from a
vacuole joins the
cell membrane
and expels the
material the
vacuole
contained.
QuickTime™ and a
Animation decompressor
are needed to see this picture.
Click to Show Movie
Pinocytosis
Engulfing small
particles and/or
liquid.
 “cell drinking”

Phagocytosis
Engulfing large
particles or
organisms.
 “cell eating”

Question 1
The diffusion
of water
across a
selectively
permeable
membrane is
called
__________.
Selectively
permeable
membrane
A. active transport
C. exocytosis
Water molecule
Sugar molecule
B. endocytosis
D. osmosis
The answer is D,
osmosis.
Regulating the
water flow
through the
plasma
membrane is an
important factor
in maintaining
homeostasis
within the cell.
Before osmosis
Selectively
permeable
membrane
After osmosis
Water molecule
Sugar molecule
Question 2
What is the expected result of having an animal
cell in a hypertonic solution?
A. The cell shrivels up.
B. The plasma membrane shrinks away from
the cell wall.
C. The cell swells up.
D. The cell retains its normal shape.
The answer is A. In a hypertonic solution, cells
experience osmosis of water out of the cell.
Animal cells shrivel because of decreased
pressure in the cells.
H2O
H2O
Water molecule
Sugar molecule
Question 3
A grocer mists the celery display with water to
keep it looking fresh. What type of solution is the
celery now in?
A. isotonic
B. hypotonic
C. hypertonic
D. exotonic
The answer is B. Plant cells contain a rigid cell
wall and do not burst even in a hypotonic
solution.
Question 4
Transport of materials across the plasma
membrane that does not require energy from the
cell but does use transport proteins is called
__________.
A. osmosis
B. simple diffusion
C. facilitated diffusion
D. active transport
Channel
proteins
Plasma
membrane
Concentration
gradient
The answer is C. Facilitated diffusion is a type of
passive transport and requires no energy from
the cell.
Channel
proteins
Plasma
membrane
Concentration
gradient