Download The Cell in its Environment

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CELLULAR
TRANSPORT
The Cell and its Environment
Cellular Transport
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The Cell in its Environment
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The Cell Membrane
Selectively permeable membrane
Lipids
Transport
Proteins
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SELECTIVELY PERMEABLE
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Diffusion across cell membrane
Can it be an impenetrable boundary?
IN
food
carbohydrates
sugars,
proteins
amino acids
lipids
salts, O2, H2O
NO!
OUT
OUT
IN
waste
ammonia
salts
CO2
H2 O
products
cell needs materials in & products or waste out
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Channels through cell membrane
inside cell
H 2O
NH3
salt
aa
sugar
outside cell
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Cellular Transport
Two Kinds
1. Passive Transport
2. Active Transport
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Types of Cellular Transport
Passive Transport - cell doesn’t use energy
Weeee!!
!
1. Diffusion
2. Facilitated Diffusion
high
3. Osmosis
Active Transport - cell uses energy
1. Protein Pumps
This is
gonna
2. Endocytosis
be hard
high
work!!
3. Exocytosis
low
low
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PASSIVE TRANSPORT
Diffusion
Facilitated Diffusion
Osmosis
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Passive Transport
Diffusion is the
movement of molecules
from an area of higher
concentration to an
area of lower
concentration.
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Diffusion of Molecules
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Diffusion
 Diffusion

movement from high  low concentration
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Facilitated Diffusion
• Diffusion through protein channels
• channels move specific molecules across
cell membrane
facilitated = with help
open channel = fast transport
high
low
“The
Bouncer”
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Passive Transport Comparison
Facilitated
diffusion
(Channel
Protein)
Diffusion
(Lipid Bilayer)
Carrier Protein
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Osmosis
The movement of water across a
cell membrane
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Isotonic
the
concentration
of water
outside and
inside the cell
is equal.
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Hypotonic Solution
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Hypotonic
the concentration of
water outside the
cell is greater than
the concentration of
water inside the cell;
water will flow into
the cell, causing it to
swell
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Hypotonic Solution
Solute less
than Water
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Water moves from the solution to inside of
the cell. The cell Swells and bursts open.
Cytolysis is cell bursting.
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Hypertonic
the concentration of
water outside the
cell is lower than the
concentration of
water inside the cell;
therefore water will
flow out of the cell,
causing it to shrink
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Hypertonic Solution
Solute greater
than Water
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Water moves from inside the cell into the
solution and the cell shrinks.
Plasmolysis cell shrinking
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Managing water balance
Cell survival depends on balancing water
uptake and loss.
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Concentration of Solution
• Direction of osmosis is determined by
comparing total solute concentrations
Inside the Cell
Solution
Tonicity
Solute
Hypertonic

Water
Solute


Hypotonic


Isotonic
=
=

=
Movement of
Water
Water
(Cell Condition)

Water goes in
the Cell
(Cell Shrivel)

Water goes out
the Cell
(Cell Bust)
=
Normal Cell
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How Organisms Deal with
Osmotic Pressure
Bacteria and plants have
cell walls that prevent
them from over-expanding.
In plants the pressure
exerted on the cell wall is
called turgor pressure.
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How Organisms Deal with Osmotic Pressure
•A protist like paramecium
has contractile vacuoles
that collect water flowing in
and pump it out to prevent
them from over-expanding.
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How Organisms Deal with Osmotic Pressure
• Salt water fish pump salt out of their
specialized gills so they do not
dehydrate.
• Animal cells are bathed in blood.
Kidneys keep the blood isotonic by
remove excess salt and water.
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ACTIVE TRANSPORT
Protein Channels
Endocytosis and Exocytosis
Phagocytosis and Pinocytosis
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Active Transport
 actively moves molecules to
where they are needed
 Movement molecules from
an area of low concentration
to an area of high
concentration (Low  High)
 cell uses energy
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Types of Active Transport
Protein Pumps
Endocytosis
Exocytosis
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Protein Pumps
transport proteins that
require energy to do
work
Sodium / Potassium
Pumps are important in
nerve responses.
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Endocytosis:
taking bulky
material into
a cell
• Uses energy
• Cell
membrane
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TWO KINDS:
1. Phagocytosis – cell enguls
solid particles of food
“cell eating”
2. Pinocytosis – cell takes in
droplets of fluid
“ Cell drinking”
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Phagocytosis
Pinocytosis
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3. Exocytosis: Forces
material out of cell in bulk
• membrane surrounding
the material fuses with
cell membrane
• Cell changes shape –
requires energy
• EX: Hormones or
wastes released from
cell
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Cytoplasm