Transcript WEEK 12 CP Cell_Transport_Bio

Tuesday
• When is all late work due????
• What does the cell membrane do?
Bio NOTES: Cell Transport
The Plasma (Cell) Membrane:
• Found in prokaryotic and eukaryotic cells
• Surrounds the cell, providing protection and
support
• Regulates what enters and leaves the cell
• Selectively Permeable: only allows certain
materials through
The plasma membrane is made of a lipid bilayer
(2 layers of lipids)
Important Terms
Concentration gradient - a difference in concentrations
- movement across the concentration gradient
can be from low to high OR high to low
Equilibrium - when solution levels
are balanced (similar to homeostasis)
There are 2 main types of transport:
1. Passive transport
- movement from high to low concentration
- no energy required
2. Active transport
- movement from low to high concentration
- energy required
Types of Passive Transport
Diffusion:
- movement of particles from
high to low
- no energy required
- small, nonpolar molecules
can diffuse easily (CO2 and O2)
Facilitated Diffusion:
- movement of molecules from high to low with the
help of proteins
- no energy required
- occurs with molecules that
are too large, are polar,
or are ions (- or +)
Types of Passive Transport
Osmosis:
- movement of water molecules
from high to low
- no energy required
The net direction of osmosis
depends on the solute
Cell
concentration
- a high solute
low water
concentration means
high solute
there is a lower
concentration of water
high water
low solute
Active Transport
• movement of molecules from low to high
concentration up the concentration gradient
• requires energy to go “against the flow”
• sometimes the cell needs to have a different
concentration of substances on either side of the
membrane
Types of Active Transport
• Cell Membrane Pumps – transport proteins pump
molecules across the membrane
• Endocytosis – taking materials and nutrients into
the cell
• Exocytosis – releasing large amounts of material
out of the cell, such as waste or proteins
Endocytosis and Exocytosis
Passive transport Active transport
• No energy required
• Movement from
high to low area of
concentration
• Molecules move
with concentration
gradient
1.Diffusion
2.Osmosis
3.Facilitated diffusion
• Requires energy
• Movement from low
to high area of
concentration
• Molecules move
against
concentration
gradient
1.Sodium-potassium
ion pump
2.Endocytosis
3.Exocytosis
Follow Up Questions:
1. The cell is surrounded by a plasma membrane, what
does the plasma membrane do?
Transports materials into and out of the cell
2. Why is it important to regulate what enters and leaves
the cell?
Import materials such as oxygen and food
Export excess materials and waste
To maintain homoeostasis
3. What does it mean to be Selectively Permeable?
Only certain materials can pass through
4. What molecule diffuses the easiest through the plasma
membrane?
Water
5. What are the major parts of the plasma membrane?
Lipids, Proteins, and Carbohydrates
• Two types of transport?
• Which type requires energy?
Tuesday
• What is the difference between active and
passive transport?
• Name the 3 types of passive transport.
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
• Water is so small and there is so much
of it the cell can’t control it’s movement
through the cell membrane
Next lets see how different conditions
(iso/hypo/hyper) can affect a cell by
osmosis …
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 is
equal to cell contents
Hypertonic
90% h2o
10% solute
Solute outside High
Solute Inside Low
60% h2o
40% solute
Water outside Low
Water inside High
Hypotonic
50% h2o
50% solute
Solute outside Low
Solute Inside high
60% h2o
30% solute
Water outside high
Water inside low
The Effects of Osmosis
In hypotonic solutions:
- solute concentration is lower outside the cell
- water flows into the cell
- cell swells Animal cells will Burst
- Plant Cells are the most stable due to cell wall
In hypertonic solutions:
- solute concentration is higher outside the cell
- water flows out of cell
- cell shrinks or shrivels
Hyper people are skinny
In isotonic solutions:
- solute concentration is the same inside
and outside the cell
- water flows in and out equally
- cell remains the same
Animal cells are the most stable
closer
• High solute outside =
• Low solute outside =
• Equal solute =