Transcript Cell Membranes and Transport

4.1 Cell Membranes and Transport
KEY Concepts
1. How Does the Cell Membrane
Help Maintain Homeostasis?
2. What is osmosis and how does it
affect living organisms?
3. What is Difference between
Passive and Active Transport?
Language/Vocab
• Homeostasis
• Diffusion
• Osmosis
• Active transport
• Passive transport
• Facilitated Diffusion
Homeostasis
• Balance all
organisms must
maintain with their
surrounding
environment
• What factors do
humans have to
regulate to maintain
homeostasis?
Homeostasis
• Individual cells
maintain
homeostasis by
controlling what
enters and exits the
cell
• What structure
controls what
enters and exits the
cell?
The Cell Membrane
• Made of a bilayer of phospholipids
• Phospholipids have a hydrophobic tail (water
fearing) and hydrophilic head (water loving).
• Proteins are embedded in the membrane to help
move materials in-and-out of the cell.
The Cell Membrane
• Why is the cell membrane called a fluidmosiac?
The Cell Membrane
• Cell membranes are
SELECTIVELY
PERMEABLE – what
does this mean?
• How is the strainer
selectively permeable?
Passive vs. Active Transport
Passive transport:
• Movement across a
cell membrane that
DOES NOT USE
ENERGY
• Moves molecules
where they
naturally want to go
Active transport:
• Movement across a
cell membrane that
USES ENERGY
• Forces molecules
to move where they
do not want to go
Diffusion
• Movement of molecules through the cell
membrane
• Molecules move from an area of HIGH
CONCENTRATION to an area of LOW
CONCENTRATION
• Passive transport
• Why is this passive transport?
Diffusion
• What direction will the molecules move?
• EQUILIBRIUM is reached when
concentrations are equal on both sides of
the cell membrane
Osmosis
• Diffusion of WATER molecules through the
cell membrane
• Water always diffuses from an area of LOW
SOLUTE CONCENTRATION to an area of
HIGH SOLUTE CONCENTRATION
• Passive transport
• What is a solute? A solvent?
Osmosis
Osmosis
Hypotonic solution:
• Solute
concentration is
lower on the
outside of the cell
than inside the cell.
• Which direction will
water move?
Osmosis
Hypertonic solution:
• Solute
concentration is
higher on the
outside of the cell
than inside the cell.
• Which direction will
water move?
Osmosis
Isotonic solution:
• Solute
concentration is
equal on both sides
of the cell
membrane.
• Which direction will
water move?
Osmosis and Plant Cells
• Plant cells require a hypotonic environment
so water moves into the cell and the cell
swells
• Swelling of the cell builds up turgor
pressure
• Why is turgor pressure important?
Osmosis and Plant Cells
• Plant cells in hypertonic environments lose
water and the cell shrivels up
• Shriveling of the cell is called plasmolysis
• Why is it important for plant cells to prevent
plasmolysis?
Osmosis and Plant Cells
• Which plant has plasmolysized cells and which as
turgid cells?
Osmosis and Animal Cells
• What would happen to animal cells in
hypotonic and hypertonic environments?
Summary of Osmosis
Facilitated Diffusion
• Movement of molecules in and out of the
cell using a carrier protein
• Molecules move from an area of HIGH
CONCENTRATION to and area of LOW
CONCENTRATION
• Why would molecules need help from a
carrier protein?
Facilitated Diffusion
• How is facilitated diffusion different from simple
diffusion?
• How are they the same?
Active Transport
• Movement of molecules across the cell
membrane that requires energy.
• Molecules move from an area of LOW
CONCENTRATION to an area of HIGH
CONCENTRATION.
• Why does this require energy?
Active Transport
• Which way will the molecules move in
active transport?
Endocytosis
• Movement of large molecules into a cell by
engulfment
• Pinocytosis - engulfing a liquid (“Cell
drinking”)
• Phagocytosis - engulfing a solid (“Cell
eating”)
Summary of Cell Transport