Download Ch. 3 Cell Transport Notes

Cell Transport
Intro Video
What is the purpose for the cell membrane in all
cells?
Is Selectively Permeable
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Allows for the passage of some substances based on size
and the concentration of materials on either side of the
membrane
Made up of a double layer of phospholipids with proteins
floating through it
What are the two main parts of the
cell membrane?
• Phospholipids
• Proteins
• A phospholipid has a head and a tail
region. The tails are made up of the
fatty acid chain of a lipid
• Outer part of the membrane is
made up of polar (charged),
hydrophilic (water loving) heads.
• Inner part of membrane is made up
of nonpolar (not charged),
hydrophobic (water fearing) fatty
acid tails
Head
Tail
Phospholipid
Head
Tails
Head
• Due to the hydrophobic
nature of the inside of the
membrane:
– Cells do not go into solution
with the environment.
– Water can’t get past the
hydrophobic tails. Allows for
the structure of the cell
• Materials like water, glucose,
some amino acids, and ions
(Na+, Cl-, K+), can’t pass
through the membrane
without going through the
protein channels located
throughout the membrane
• In the "fluid mosaic model" of membrane structure says
that the molecules within the membrane move around.
– Phospholipids regularly move sideways & flip
– Proteins can not flip around but instead float like floats on water
Rap
1. Hydrophobic means
– Water fearing
– Water molecules will be repelled
2. Hydrophilic means
– Water loving
– Water molecules will be attracted to it
3. Polar means
– Has a positive end and a negative end to the
molecule
How does the cell membrane create a barrier
that is also selectively permeable?
1. Inside of the membrane is made up of?
– Hydrophobic fatty acid tails
– Nonpolar
– Repel polar molecules and ions
2. Outside of the membrane is made up of?
– Hydrophilic heads
– Attract polar molecules like water and ions
The Cell Membrane is Selectively Permeable
• The membrane allows some materials to pass
and not others.
• Maintains homeostasis with the cell
• It can control what is coming in a going out of
the cell
• It regulates permeably by:
– The size of their pores
– The size of the molecule (monomers can pass
through while polymers can’t)
– The concentration of molecules on either side of the
membrane
– Polarity of the molecules
What are the four factors that determine what
can get through the cell membrane?
1. The size of their pores
2. The size of the molecule (monomers
can pass through while polymers
can’t)
3. The concentration of molecules on
either side of the membrane
4. Polarity of the molecules
Label the parts of the Cell Membrane:
Head, Fatty Acid tails and Proteins
Indicate which part of the cell membrane is
hydrophilic and which part is hydrophobic, and
then nonpolar and polar
Passive Transport
• The movement of molecules without requiring
an energy input to make it happen.
– Like going down a hill. You don’t need energy
• Based strictly on the concentration gradient
– The difference between the concentration of
molecules from one location to another
– Air freshener
Diffusion
• The movement of molecules from a region of
higher concentration to a region of lower
concentration without the need for added
energy.
• Depends on the kinetic energy of molecules
• Goes down (or with) the concentration gradient
Potassium Permanganate is placed in the
middle of a dish of water. What will happen?
• Crystals dropped in the
middle of the water will
start to diffuse to areas of
lower concentration without
the need of additional
energy.
• Eventually, the molecules
will be evenly distributed
– Reach Equilibrium – the same
distance between molecules
throughout
Why is diffusion considered a form of Passive Transport?
It is passive transport because molecules move
from where they are highly concentrated
(more solutes) to where they are in lower
concentration (low solutes) (with the
concentration gradient) without the need for
energy.
Do you need energy to ski down a hill?
How does water get into plant cells?
How does water get into or out of our skin?
Osmosis is the movement of
water through a membrane
from an area of high water
concentration to an area of
less water concentration
– or from where there are less
solutes in solution to an area
of where there are more
solutes in solution
What happens when you eat salty foods and sugary drinks?
You will be really thirsty!!!!
• This is because your food had a high solute
concentration of salt and sugar (hypertonic).
• Your cells will be a lower solute concentration and
basically made up of water (hypotonic).
• Water will move from where there are more water
molecules and less solutes (hypotonic) or to where
there are more solutes and less water (hypertonic)
• The cells will start to lose water and you will be
thirsty!
Glen’s Osmosis song
• The first diagram has very few solute molecules outside the cell and
a lot inside the cell
– Hypotonic solution
– Water will flow into the cell and cell will enlarge
• The diagram on the right has a lot of solutes outside the cell and
very few inside the cell
– Hypertonic solution
– Water will flow out of the cell and cell will shrivel
• The middle diagram has the same number of solutes on either side
of the cell membrane
– Isotonic solution
– Water molecules will continue to flow into and out of the cell
– The net movement of molecules is zero.
Osmosis lab with Osmosis Grape and Gummy Bears
Predict what will happen in the U-Tube
Video
Sometimes, molecules need help getting through the
membrane due to those hydrophobic, nonpolar tails
Facilitated Diffusion
• Molecules that are polar cannot pass through the
nonpolar tails of the cell membrane. They need help to
get through
• Glucose, Water, ions like Na+ and Cl• Will pass through protein channels which shield the
polar molecules from the nonpolar tails. Like going
through a tunnel
Why is facilitated diffusion necessary?
• Since the inside of the cell membrane is made up
of fatty acid tails which are nonpolar and
hydrophobic, molecules like water, glucose and
ions such as Na+ and Cl- can’t pass through it.
• The protein channels protect them from the
nonpolar tails.
Label the Carrier Proteins and the Channel
Proteins. Draw an arrow to indicate the
direction of flow of the solutes
Diffusion
Facilitated Diffusion
Active Transport
• Some molecules need to be
concentrated inside the cell or
removed from the cell (such as
wastes or products of the cell like
glucose, lipids and proteins)
• These molecules will move from
where they are in low
concentration to where they are
in higher concentration
• Energy will be needed to go
against or up the concentration
gradient
– Like going up a hill. Energy will be
needed
ATP is an energy transport molecule.
• It transfers a phosphate group to another
molecule and transfers energy with it.
• Powers all cellular activity
Sodium-Potassium Pump
Moves Na+ out of the cell and K+ into the cell from
low to high concentration
Why is the Sodium – Potassium pump
considered to be a form of Active Transport
Na+ is in higher concentration outside the cell
than inside of it.
K+ is in higher concentration inside the cell
than outside of it.
Both are moved through protein channels from
where they are in low concentration to where
they are in high concentration.
To go up the concentration gradient, ENERGY
(ATP) is needed.
To walk back up the ski hill takes ENERGY!!
How many Sodium ions leave the cell?
How many Potassium ions enter the cell?
What is needed to change the shape of the protein carrier and move
the molecules against the concentration gradient?
Endocytosis and Exocytosis
• Energy will be
needed (by ATP)to
move large
molecules like
starch or proteins or
small organisms like
bacteria or
paramecium into or
out of a cell
Endocytosis
Endocytosis
– Is the process of taking in liquids or fairly large molecules into
a cell by engulfing them in a membrane
– Cell membrane forms a pocket around the substance which
will become a vesicle inside the cell
– Lysosomes fuse with the vesicles and puts digestive enzymes
into the vesicle
Phagocytosis (“cell eating”)
• Engulfing of bacteria, viruses or large
molecules
– How white blood cells and amoeba get their
food.
Amoeba phagocytizing a Paramecium
A White Blood Cell (Macrophage)
Phagocytizing bacteria
Exocytosis
• Opposite of Endocytosis
• Release of substance through the cell membrane
What is the difference between Endocytosis
and Exocytosis?
Endocytosis means coming
into the cell process.
This is the engulfing of
molecules/organisms
into a cell into vesicles
Exocytosis means leaving
the cell process
The vesicles with
macromolecules or
wastes are sent out of
the cell
Label the diagrams either exocytosis
or endocytosis.