Osmosis, Diffusion, Active Transport

Osmosis, Diffusion,
Active Transport
DO NOW (Copy GQ)
I can explain how materials move into
and out of the cell. (Pages 78-81)
 GQ-How do molecules cross the plasma
Cell Membrane (Transport) Notes
Cell Membrane and Cell Wall:
• ALL cells have a cell membrane made of proteins and lipids
protein channel
Layer 1
Layer 2
lipid bilayer
protein pump
• SOME cells have cell membranes and cell walls – ex: plants, fungi
and bacteria
Cell Wall
• Plant cells have a cell wall
made of cellulose – that
cellulose is fiber in our diet
• Bacteria and fungi also
have cell walls, but they
do not contain cellulose
• Cell membranes and cell
walls are porous allowing
water, carbon dioxide,
oxygen and nutrients to
pass through easily
Function of the Cell Membrane:
• Cell membrane separates the components of a cell
from its environment—surrounds the cell
• “Gatekeeper” of the cell—regulates the flow of
materials into and out of cell—selectively permeable
• Cell membrane helps cells maintain homeostasis—
stable internal balance
Diffusion, Osmosis and
Concentration Gradient
Diffusion – the movement of a substance from a high
concentration to a low concentration
Osmosis – the movement of WATER from a high
concentration to a low concentration.
Concentration Gradient – the difference in
concentration between a region of high concentration
and a region of lower concentration
Passive or Active Transport:
Passive Transport - does not require cell
Examples: Diffusion, Facilitated diffusion and
Active Transport Requires cell energy (ATP)
Examples: Carrier mediated active transport,
Endocytosis and Exocytosis
Methods of Transport:
1. Diffusion: the random movement of
particles of a solute from an area of higher
concentration to an area of lower concentration.
Particles always move with (down) a concentration
gradient (the difference in concentrations across a
 Passive transport.
Diffusion stops at equilibrium (when the concentrations across
a membrane are equal).
The movement of molecules continues at equilibrium but the #
of molecules moving across the membrane remains the same.
The rate of transport is dependent on:
1) if the material is solid, liquid or gas.
2) the size of the molecules.
3) temperature
Examples of molecules that can diffuse through the bilayer:
carbon dioxide, oxygen, water but very, very slowly.
Diffusion through a Plasma
Osmosis: the diffusion of water through a
selectively permeable membrane.
Passive transport
 Water molecules move from a higher concentration
OF WATER to a lower concentration OF WATER.
 Water will move to where there is a greater amount
of solute because there is less water there
Isotonic Solution
Isotonic solutions: the
concentration of solute inside and
outside of the cell is the same.
Water in = Water out
No net movement of water.
Molecules in equilibrium.
Normal state for animal cells.
Cell in homeostasis.
Hypotonic Solution
Hypotonic solutions: the concentration of solute is
lower outside the cell than inside the cell.
Have more water outside the cell so water moves into the cell
Causes an increase in pressure inside the cell: called turgor
pressure (plants) or osmotic pressure (animals).
Increase in pressure in animal cells causes them to swell or
even burst; gives plant cells shape and support.
Example Hypotonic
Water enters cell.
Cell swells and bursts
Give plant cells shape
and support.
Hypertonic Solution
Hypertonic solutions: the concentration of
solute is higher outside the cell than inside the
Have more water inside the cell so water moves out
of the cell
 Causes a drop in turgor or osmotic pressure: called
 Plasmolysis causes animal cells to shrivel up and
plants to wilt.
Hypertonic Example
Water exits cell.
Cell shrinks
(plasmolysis) due
to water loss.
The effects of osmotic pressure
Hypo, Iso, Hyper
The effects of osmotic pressure in a
plant cell
 Discuss
today’s GQ with a neighbor.
 Next, complete the Brain Pop quiz
NOW or for HW.
 Write
a summary of the key points from
yesterday’s lesson. Be prepared to
SHARE this with the class.
Learning Menu
Appetizer: Brain Pop/Active Transport
 Main Course:
Cell Transport PP
Bead Diffusion Quick Lab (pg. 79)
 Dessert: CFU Questions
Facilitated Diffusion
Particles always move with
(down) a concentration
Uses transport/channel
Passive transport.
Usually for specific molecules
such as glucose.
Facilitated diffusion stops at
Active transport
Active Transport: requires energy in the form
of ATP.
Capable of moving solute particles against the conc.
gradient (from low conc. to high conc.)
 Uses transport/carrier proteins (protein pumps)
embedded in the plasma membrane.
 Carrier proteins are specific for the molecules that
they allow through. The carrier protein changes
shape which requires energy (ATP).
Active Transport against the
concentration gradient
Active Transport
Endocytosis: a process of taking material into
the cell by means of infoldings, or pockets, of
the cell membrane (usually putting them into a
Phagocytosis -“Cell eating”
Nonspecific molecules
 Intake of solids
Pinocytosis –”Cell Drinking”
Nonspecific molecules
 Intake of small droplets of liquid
Active Transport
Exocytosis (reverse endocytosis): a process in
which the membrane of the vacuole
surrounding the material fuses with the cell
membrane, forcing the contents out of the cell.
Turn to page 79.
Work with your group to complete the quick lab &
answer the questions (#3) in your notebook.
Next, each person must answer 2 of the CFU
questions for today.
CFU- Pick 2
How would you compare/contrast diffusion and
How would you explain the 3 types of solutions?
What’s the difference between & some examples
of active/passive transport?
Lesson Reinforcements:
Ed Helper Diffusion/Osmosis
HOLT Ch. 3/Section 1 Guided Reading
Osmosis/Diffusion Study Guide
Study Island “Cell Structure & Function”