Cell Transport
Learning Objectives
1. List at least 2 purposes of the cell membrane.
2. Name the 3 types of passive transport.
3. Name the 2 types of active transport.
4. Describe the difference between passive & active
transport in 2-3 well-written sentences.
5. Write a short paragraph on how osmosis plays a role
in the homeostasis of red blood cells using the words:
hypertonic, hypotonic, and isotonic.
Cell Membranes
• All cells have a cell membrane
• Functions:
a. Controls what enters and exits the cell (it is selectively permeable) to maintain an internal balance called homeostasis
b. Provides protection and support for the cell TEM picture of a real
cell membrane.
The “Fluid Mosaic Model”
https://youtu.be/Qqsf_UJcfBc and
http://www.stolaf.edu/people/giannini/flashanimat/lipids/mem
brane%20fluidity.swf
Passive & Active Transport
• Cell membrane = semipermeable (selectively permeable). Some substances pass through while others can’t
• Materials can enter/exit the cell via (1) passive transport or (2) active transport.
Types of Cellular Transport
• Passive Transport
Cell doesn’t use energy1. Diffusion
2. Facilitated Diffusion
3. Osmosis
• Active Transport
Cell does use energy1. Protein Pumps
2. Endocytosis
3. Exocytosis
High
concentration
Low concentration
Weeee!!!
High
concentration
Low concentration
This is
hard
work!!
Passive Transport: Diffusion
Cell Membrane
Inside Cell
Outside Cell
Solutes
Higher concentration of solute
on one side of the membrane
than the other
Diffusion causes net movement
of solute particles from the side
of the membrane with the higher
solute concentration to the side
with the lower solute
concentration.
At equilibrium, particles move
equally in both directions, so
there is no net change.
Diffusion: Example
Food coloring in hot/cold water.
https://www.youtube.com/watch?v=9ghYur0vqgE
Passive Transport: Facilitated Diffusion
Facilitated Diffusion Example
https://www.youtube.com/watch?v=vKGN_Zhz8AY
Passive Transport: Osmosis
aquaporin
water
cell membrane
sugar
Passive Transport
Osmosis – diffusion of water (high low concentration)
http://kids.britannica.com/comptons/art-53766/An-example-of-osmosis-occurs-when-a-sugar-solution-and
The sugar
(solute)
molecule is
too big to
move across
the
membrane.
POP QUIZ!!!
What is the
solvent?
Solute: what is being dissolvedSolvent: what dissolves the solute.
Osmosis
Effects of Osmosis on
Life
There are 3 types of
solutions that involve
water and how they
affect the cell.
1. Hypertonic Solution: the solution the cell is placed in
has less water than the cell (more solute; less water)
2. Hypotonic Solution: the solution the cell is placed in
has more water then the cell (less solute; more water)
3. Isotonic Solution: the solution the cell is placed in has
equal amount of water as the cell (equilibrium!)
Osmosis in Cells
Isotonic Hypertonic Hypotonic
In what type of solution are these cells?
A CB
Hypertonic Isotonic Hypotonic
Hypotonic Solution
Hypotonic: The solution has a lower concentration of
solutes and a higher concentration of water than inside the
cell. (Low solute; High water)
Result: Water moves from the solution to inside the cell): Cell
Swells and bursts open (lyse)!
• Osmosis Animations for isotonic,
hypertonic, and hypotonic solutions
Hypertonic Solution
Hypertonic: The solution has a higher concentration of
solutes and a lower concentration of water than inside the
cell. (High solute; Low water)
Result: Water moves out of the cell into the solution:
Cell shrivels!
• Osmosis Animations for isotonic,
hypertonic, and hypotonic solutions
shrinks
Isotonic Solution
Isotonic: The concentration of solutes in the solution is
equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell
remains same size! (Dynamic Equilibrium)
• Osmosis Animations for isotonic,
hypertonic, and hypotonic solutions
How Organisms Deal with Osmotic Pressure
• Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure.
• A protist like the paramecium has contractile vacuolesthat collect water flowing in and pump it out to prevent them from over-expanding.
• Salt water fish pump salt out of their specialized glands in gills so they do not dehydrate.
• Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.
• Paramecium (protist) removing excess water video
Active Transport
Protein pumps Endocytosis Exocytosis
Example: Sodium /
Potassium Pumps are
important in nerve
responses.
Example for endocytosis is the
leukocytes, neutrophils, and
monocytes can engulf foreign
substances like bacteria
Example secretion of enzymes
from pancreatic cells and
hormones from endocrine
glands
ACTIVE TRANSPORT
• Moves substances from lower concentration to higher concentration.
• Requires ENERGY.
– What is the source of energy?
Types of Active Transport
1. Protein Pumps -
transport proteins that
require energy to do work
• Example: Sodium /
Potassium Pumps are
important in nerve
responses.
Sodium Potassium
Pumps (Active
Transport using
proteins)
Protein changes
shape to move
molecules: this
requires energy!
Types of Active Transport
2. Endocytosis: taking bulky material into a cell by forming a vesicle
• Uses energy
• Cell membrane in-folds around food particle
• “cell eating”
• forms food vacuole & digests food
• This is how white blood cells eat bacteria!
Types of Active Transport
3. Exocytosis: Forces material out of cell in bulk
• Membrane surrounding the material fuses with cell membrane
• Cell changes shape –requires energy
• Ex: Hormones or wastesreleased from cell
Endocytosis &
Exocytosis
animations
Endocytosis
Active Transport vs. Diffusion
Compare and contrast active transport and diffusion.
More Vocab!!
Plasmolysis: shrinking of the cytoplasm away from the wall
of a living cell
Turgor pressure: the pressure exerted on a plant cell wall
by water passing into the cell by osmosis
Crenation: a process resulting from osmosis in which red
blood cells, in a hypertonic solution, shrink/shrivel
Lysis: cell rupture/bursting