The cell membrane transports material across
it using a variety of methods.
Review: What is the term used to describe
how the membrane can control what moves
across?
◦ Selectively permeable or semi-permeable
There are two types of
transport:
◦ Active The cell needs to use ATP for
energy to move something across
the membrane
Molecules move up the
concentration gradient (from low
to high concentration)
◦ Passive the cell moves materials across
the membrane without any use of
energy (ATP)
Molecules move down the
concentration gradient (from high
concentration to low
concentration)
There are four types of passive transport:
1.
2.
3.
4.
Diffusion
Osmosis
Facilitated Diffusion
Filtration
There are two main types of active transport:
1. Solute pumps- protein channels
2. Vessicular transport -moves in vessicles (bubbles)
Works with small non-polar molecules
They are small enough to slip through the
membrane on their own
They are drawn across to the area with fewer
of the same molecule
Examples: fatty acids, urea (cellular waste),
carbon dioxide and oxygen
System example◦ In your lungs, blood carries
carbon dioxide waste made in
your cells by cellular
respiration.
◦ The carbon dioxide is found in
large quantities in your blood
and low quantities in the lungs.
◦ It moves out of the blood into
the lungs.
◦ Oxygen is in high quantities in
the lungs, it moves to the
blood, which is low in oxygen
and then can be delivered to
your cells.
Basic diffusion of water
Water moves from a high
concentration of water, to a
low concentration of water.
Water moves through a
transport protein called an
aquaporin
It always moves towards an
area that has a higher
concentration of solutes.
Osmosis is determined by a
liquids tonicity- how much
solute it has
◦ Equal concentrations of water and
solutes on both sides of the
membrane (isotonic)
◦ This is concentration is the goal for
a cell’s homeostasis.
Osmosis is determined by a liquids tonicityhow much solute it has
◦ A high concentration of water means there are low
concentrations of solutes (hypotonic solution)
◦ If a cell is found in a hypotonic solution, it has more
solutes inside the cell than outside, so the water
will rush into the cell and could cause it to burst or
pop like a balloon with too much air (lyse)
Osmosis is determined by a liquids tonicityhow much solute it has
◦ A low concentration of water means there are high
concentration of solutes (hypertonic)
◦ If you put a cell in a hypertonic solution, it has less
solutes in it than outside, so water moves out of the
cell causing it to shrink or crenate
Facilitated= with help or aide
This is diffusion of glucose.
Glucose is too large to move through the cell
membrane on its own, so it uses a transport
protein.
◦ The protein looks like a closed gate
◦ Glucose binds to the protein, changing the protein’s
shape- opening the “gate” and allowing glucose
into the cell
This occurs in the first part of urine formation
in your kidneys.
High blood pressure, pushes anything
dissolved in your blood into the kidney tubule
so your blood is filtered, like you would filter
minerals out of your water in a Brita.
Goes against the gradient so it requires the
use of energy!
There are two main types of active transport:
1. If the cell is moving a small structure or molecule
across the membrane to a low concentration, it
uses solute pumping (a transport protein)
2. If the cell is moving large structures or large
amounts of molecules to a low concentration, it
uses vessicular transport (a membrane bound
“bubble” that holds the molecule.
Uses a protein pump to move ions and other
polar molecules across the membrane
Example: Sodium-potassium pump
◦ Cell moves sodium and potassium across the
membrane to send electrical messages down a
neuron (nerve cell)
◦ Sodium and potassium can move through the
membrane on their own if they diffuse to a lower
concentration
◦ The cell has to use energy to restore charges, by
moving the ions back to their original position
Uses a membrane-bound vessicle (bubble) to
transport material across the membrane.
When the vessicle reaches the cell membrane,
it fuses with it and releases the molecule.
Two types:
◦ Exocytosis- if the molecule is moving out of the cell
or exiting the cell
◦ Endocytosis- if the molecule is moving into the cell
There are two reasons the cell uses
endocytosis:
1. It’s taking in a bacterium or virus during an
immune response- called phagocytosis
During this process the cell will lyse the foreign material
2. It’s bringing in large amounts of solutes,
dissolved in water- called bulk-phase endocytosis
Two Types of Transport Passive
Uses energy in the form
of ATP?
How it moves in
regards to
concentration?
Examples
Active
Diffusion:
Diffusion
•
•
Works with what type of molecule?
Why do these molecules move through the membrane easily?
•
•
Examples of molecules that diffuse?
Example of how this works in a system:
Osmosis:
Osmosis
• Works with what type of molecule?
• How do these molecules move through the membrane?
• Regulated by tonicity- def:
• Isotonic:
• Hypotonic:
• Hypertonic:
Facilitated Diffusion:
Diffusion def•
Works with what type of molecule?
•
How does this molecule move through the membrane?
Filtration:
Filtration
• Works in what organ/system?
• What complementary system works to achieve this? How?
1. Solute pumping:
•
•
Definition:
Example- Sodium potassium pump
•
Explain how it works in a nerve:
2. Vessicular Transport:
Transport
• Definition:
• Explain how it works:
• Two types named based on movement:
1. Exocytosis :
2. Endocytosis:
a. phagocytosis
b.bulk-phase endocytosis