Warm Up
• Last week, we compared the cell to a complex
factory.
• Why is it important for factories to get
deliveries?
• How do you think the cell gets “deliveries”?
Cell Membrane
• Gatekeeper
• Regulates what comes in and out
of the cell
• Main components: proteins and
phospholipids
• The cell membrane is selectively
permeable
• Allows some things through without energy,
but not everything
Cell Wall
• Found only in plant cells and bacteria
cells
• Main function is support
Diffusion
• The movement of molecules from
an area of high concentration to an
area of low concentration
• Molecules tend to “spread out”
• Requires no energy
Equilibrium
• When molecules are evenly
spread throughout a space
Osmosis
• The diffusion of water across a
semipermeable membrane.
• Water will travel to where there is a
lower concentration
• If you add something like salt to the solution…
Rule for Osmosis:
Water will get sucked to
wherever there is a higher
concentration of salt.
The following slides illustrate what direction water
travels if a cell is placed in different solutions.
Why is Osmosis Important?
•Osmosis is important to cell functions.
•Red blood cells use osmosis to carry
nutrients from plasma in the cell and wastes
out of the cell.
Effect on living cells
Hypertonic
Cells
There is a higher
concentration of
salt outside of the
cell so water
moves out of the
cell
Why is it
dangerous to
drink sea
water?
Cells In Different Solutions
Isotonic cells= There is an equal amount
of salt inside and outside of the cell, so
water stays in balance and cell is at
equilibrium.
Hypotonic = less
There is a higher
concentration of
salt inside of the
cell so water
rushes into the
cell.
Warm Up
• What will happen to a houseplant if you water it
with salt water (a hypertonic solution)?
• True or False: Diffusion happens naturally when
particles go from a lower concentration to an area
of higher concentration. (Think about food
coloring in water)
Passive Transport
• The movement of substances
across a cell membrane
without the use of energy by
the cell. Used for transporting
small particles
• Examples Diffusion & Osmosis
Active Transport
• Cell uses energy to move things in and out. Example:
food molecules
• Cell membrane actually opens and closes.
Active Transport Video
Check for understanding
• The prefix exo- means “out of” and the prefix
endo- means “taking in”. How do these meanings
relate to the meaning of exocytosis and
endocytosis?
Exocytosis & Endocytosis
Exocytosis: large molecules
“exit” the cell.
Ex: Waste products
Endocytosis larger
substances “enter” the
cell.
Ex: Food molecules
Two Types of Endocytosis
• Pinocytosis: the cell takes in liquid substances
• Phagocytosis- the cell takes in food particles
“phood” (food)
Check for understanding #2
Endocytosis/Exocytosis
• Taking “in” or letting “out” large
molecules by the cell
• Phagocytosis = “phood”, taking in food
particles
• Pinocytosis = liquid substances
• Organelles and functions
• Difference between animal and plant cells
• What organelles look like
Exit Slip
• Create three scenarios in which osmosis would
make water
• 1.Come into the cell
• 2. Leave the cell
• 3. Stay isotonic and balanced
• Draw a sketch of what the resulting cell would
look like