Transcript Cell_Transport_2014

Cellular Transport
Notes
Ch. 7.4
About Cell Membranes
1. All cells have a cell
membrane
2. Functions:
a. Controls what enters and
exits the cell to maintain
an internal balance called
homeostasis.
b. Provides protection and
support for the cell.
TEM picture of a
real cell membrane.
About Cell Membranes (Continued)
3. Structure of cell
membrane:
Phosphlipid Bilayer - 2
layers of phospholipids
a. Phosphate head is polar
(water loving)
b. Fatty acid tails non-polar
(water fearing)
c. Proteins embedded in
membrane
Phospholipid
Lipid Bilayer
Polar heads
love water.
Fluid Mosaic
Model of the
cell membrane
Non-polar
tails hide
from water.
Carbohydrate cell
markers
Proteins
Membrane
movement
animation
About Cell Membranes (continued)
• 4. Cell membrane has pores (holes) in it.
a. Selectively Permeable - allows some
molecules in and keeps other molecules out.
b. The structure helps it to be selective!
Pores
Structure of the Cell Membrane
Outside of cell
Proteins
Lipid
Bilayer
Transport
Protein
Animations
of membrane
Go to structure
Section:
Carbohydrate
chains
Phospholipids
Inside of cell
(cytoplasm)
Cells…
• Have to maintain a constant internal
environment (or homeostasis)
• respond to the concentration
gradient of the environment by
moving molecules across membranes
to balance inside and outside
concentrations (i.e. equilibrium) or to
stockpile more.
Transport Begins with Tonicity
Tonicity is the concentration of
dissolved solutes inside compared to
outside the cell.
1. Determine the concentration of solutes found
inside the cell
2. Determine the concentration of solutes found
outside the cell
3. Compare the two – where is the concentration
greater?
4. Molecules move from high to low!
Isotonic
• Concentration of dissolved solutes
outside the cell is equal to
concentration of the cell’s contents.
Hypertonic
• Hyper = there is a higher solute
concentration outside the cell. This will
draw water out of cell causing cell to
shrivel.
Hypotonic
• Hypo = there is a low solute
concentration outside the cell as
compared to inside the cell. This will
cause cell to swell as water moves in.
• So once we know the concentration
gradient we can start thinking about how
cells move molecules in and out of the
cell…
Types of Cellular Transport
•
Weeee!!
!
Passive Transport
cell doesn’t need to use energy
1. Diffusion (simple)
2. Facilitated Diffusion
3. Osmosis
•
•Animations of Active
Transport & Passive
Transport
high
low
Active Transport
cell needs to use energy
1. ION Pumps
2. Endocytosis
3. Exocytosis
This is
gonna
be hard
work!!
high
low
• OSMOSIS by The AMOEBA SISTERS:
• http://www.youtube.com/watch?v=EmJFgk
cbzVg&list=UUb2GCoLSBXjmI_Qj1vk-44g
Passive Transport
Active Transport
• No energy required
• Movement from high
to low area of
concentration
• Molecules move with
concentration
gradient
• Diffusion
• Osmosis
• Facilitated diffusion
• Requires energy.
• Movement from low to
high area of
concentration.
• Molecules move
against the
concentration
gradient.
• Sodium-potassium ion
pump.
• Endocytosis
• Exocytosis
Passive Transport:
1. Diffusion
Simple Diffusion
Animation
1. Diffusion: random movement
of particles from an area of
high concentration to an
area of low concentration.
(High to Low)
•
Diffusion continues until all
molecules are evenly spaced
(equilibrium is reached) - Note:
molecules will still move around
but stay spread out.
http://bio.winona.edu/berg/Free.htm
Types of
Passive Transport (high to low)
1. Diffusion
• Molecules move
from an area of
high
concentration to
an area of low
concentration
Click here for diffusion
animated explanation
Passive Transport (continued)
2. Facilitated Diffusion:
diffusion of specific particles
through transport
proteins found in the
membrane
a.Transport Proteins are
specific – they “select”
only certain molecules
to cross the membrane
b.Transports larger or
charged molecules
A
B
Facilitated
diffusion
(Channel
Protein)
Diffusion
(Lipid
Bilayer)
Carrier Protein
Types of
Passive Transport (high to low)
Facilitated
Diffusion
• Diffusion of bigger
molecules (but still
smaller than
particles) through
channel proteins
Click here for facilitated diffusion explanation
Passive Transport: 2. Facilitated Diffusion
Glucose
molecules
Cellular Transport From aHigh Concentration
High
• Channel Proteins
animations
Cell Membrane
Low Concentration
Through a 
Go to
Section:
Transport
Protein
Protein
channel
Low
Passive Transport:
3. Osmosis
Osmosis
animation
• 3. Osmosis: diffusion
of water through a
selectively permeable
membrane.
• Water moves from high
to low concentrations.
•Water moves freely
through pores.
•Solute (green) to large
to move across.
Passive Transport
Active Transport
• No energy required
• Movement from
high to low area of
concentration
• Molecules move
with concentration
gradient
• Diffusion
• Osmosis
• Facilitated diffusion
• Requires energy
• Movement from low
to high area of
concentration
• Molecules move
against
concentration
gradient
• Sodium-potassium
ion pump
• Endocytosis
• Exocytosis
Types of Active Transport
1. Protein Pumps transport proteins that
require energy to do
work
•Example: Sodium /
Potassium Pumps
are important in nerve
responses.
Sodium
Potassium Pumps
(Active Transport
using proteins)
Protein changes
shape to move
molecules: this
requires energy!
Types of
Active Transport (low to high)
Ion pump
 Ions are
stockpiled in
an already
highly
concentrated
area
Click here for Sodium-potassium pump
animation
Types of Active Transport
• 2. Endocytosis: taking
bulky material into a cell
• Uses energy
• Cell membrane in-folds
around food particle
• “cell eating”
• Think pac-man
• This is how white blood
cells eat bacteria!
Types of Active Transport
3. Exocytosis: Forces
material out of cell in bulk
cell “pooping”
• membrane surrounding the
material fuses with cell
membrane
• Cell changes shape –
requires energy
Endocytosis &
Exocytosis
animations
Endocytosis (in) & Exocytosis (out)
Summary
Passive
Transport
• No energy
required
• Movement with
the
concentration
gradient
• Diffusion,
osmosis,
facilitated
diffusion
• Maintains
equilibrium
Both
Active
Transport
• Movement
through channel
proteins
• Requires ATP
• Movement of
small ions &
molecules
• Ion pump or
endo/exocytosis
• Maintains
homeostasis
• Movement
against gradient
• Movement of
large particles
• Stockpiles
materials (extra’s)
NOW WE’LL FOCUS ON WATER
MOVEMENT BECAUSE IT MOVES
MORE FREELY THAN OTHER
MOLECULES
Notice the
sugar
molecules
are too big to
pass through
the
membrane
but water is
not
Effects of Osmosis on Life
• Osmosis- diffusion of water through a
selectively permeable membrane
Next lets see how different conditions
(iso/hypo/hyper) can affect a cell by
osmosis …
•
Hypotonic Solution
Osmosis
Animations for
isotonic, hypertonic,
and hypotonic
solutions
Hypotonic: The solution has a lower concentration of
solutes and a higher concentration of water than
inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the
cell): Cell Swells and bursts open (cytolysis)!
Hypotonic solution
• Water moves
inside of cell,
toward higher
solute
concentration
• Cell size
increases
* Note the cell is hypertonic compared to the solution around it
How will you remember?
Think hypo-hippo
A cell in a hypo- environment will swell like
a big fat hippo!
•
Hypertonic Solution
Osmosis
Animations for
isotonic, hypertonic,
and hypotonic
solutions
Hypertonic: The solution has a higher concentration
of solutes and a lower concentration of water than
inside the cell. (High solute; Low water)
shrinks
Result: Water moves from inside the cell into the
solution: Cell shrinks (Plasmolysis)!
Hypertonic solution
• Water moves
outside of the
cell, toward
higher solute
concentration
• Cell size shrinks
* Note the cell is hypotonic compared to the solution around it
•
Isotonic Solution
Osmosis
Animations for
isotonic, hypertonic,
and hypotonic
solutions
Isotonic: The concentration of solutes in the solution
is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and
the cell remains same size! (Dynamic Equilibrium)
Isotonic solution
• Water moves
equally in BOTH
directions
• Therefore, cell size
does not change
* Note the cell is also isotonic compared to the solution around it
What type of solution are these cells in?
A
B
C
Hypertonic
Isotonic
Hypotonic
Review
•
•
•
•
Hypotonic
Lower solute
concentration
outside the
cell
Water moves
in
Cell size
increases
E.g. Diluted
solution
Isotonic
• Same solute
concentration
• Water moves
in and out
• No change in
cell size
•
•
•
•
Hypertonic
Higher solute
concentration
outside the
cell
Water moves
out
Cell size
decreases
E.g. Strong
salt solution