1. Biology I:
Homeostasis and
Transport (Part 2)
Mr. Nettles

2. Agenda – Wed., Sept. 14, 2011
 Warm-Up (3 min)
 Today’s Objectives (2 min)
 Lesson (40 min)
 Wrap-Up (5 min)

3. Warm-Up
1. When both sides of a concentration gradient have an
equal concentration of molecules on each side
______________ has been reached.
2. _________________involves the use a protein carrier
to move molecules from an area of higher
concentration to an area of lower concentration.
a) osmosis, b) diffusion, c) facilitated diffusion, d) active transport
3. In your own words, define homeostasis.
(1 point Bonus!!) Explain an example related to the human body.

4. Warm-Up
1. When both sides of a concentration gradient have an
equal concentration of molecules on each side
__equilibrium__ has been reached.
2. _________________involves the use a protein carrier
to move molecules from an area of higher
concentration to an area of lower concentration.
a) osmosis, b) diffusion, c) facilitated diffusion, d) active transport
3. In your own words, define homeostasis.
(1 point Bonus!!) Explain an example related to the human body.
- the ability to maintain a stable internal (inside) environment
- People sweat to keep from overheating while exercising

5. Today’s Objectives
 I will describe three types of passive
transport.
– Osmosis, Diffusion, Facilitated Diffusion
 I will articulate one example of active
transport
 I will define: solvent, solute, solution,
hypertonic, hypotonic, and isotonic.

6. Think!!
 If the molecules can’t get
through the membrane, how else
could it become less crowded?

7. Osmosis
 Osmosis: WATER moves across a
membrane to create more space.
 Osmosis always moves water
toward the side that has MORE
molecules
 Osmosis does NOT need energy.

8. Osmosis
 Osmosis moves WATER from higher
concentration [OF WATER] to lower
concentration [OF WATER].
– Moves from more water to less water

9. Hypertonic vs. Hypotonic
Key Vocabulary
 Solute = what is being dissolved (salt, Koolaid,
other molecules)
 Solvent = what molecules are dissolved in (water or
other liquid)
 Solution = an even mixture of solute and solvent
(Koolaid drink)
 Hypertonic = high concentration of solute, low
concentration of solvent
 Isotonic = equal concentration of solute and
solvent
 Hypotonic = low concentration of solute, high
concentration of solvent

10. Hypertonic vs. Hypotonic
 If you place a normal cell in a
hypertonic solution, water will flow _?_
of the cell
 If you place a normal cell in a
hypotonic solution, water will flow _?_
the cell

12. Hypertonic vs. Hypotonic
 If you place a normal cell in a
hypertonic solution, water will flow
OUT of the cell
 If you place a normal cell in a
hypotonic solution, water will flow
INTO the cell

13. If water moves INTO a cell, the cell
gets bigger = swells, expands,
grows
- (Hypotonic solution)
If water moves OUT OF a cell, the cell
gets smaller = shrinks
- (Hypertonic solution)

14. Active Transport
 Using energyto move materials in and
out of the cell is called active
transport.
 Molecules move from areas of low
concentration to areas of high
concentration.
– Move from less crowded to more crowded

15. Active Transport:
Example: Na2+/K+ Pump
 Sodium-Potassium
Pump moves
sodium out of the
cell and potassium
into the cell using
energy.
 Important for
electric signal
between neurons.

16. Moving Across a
Membrane
 Steps to tell what kind of
transport:
1. Ask: what moves?
– If molecules move , it is Diffusion.
– If water moves, it is Osmosis.

17. Moving across a
membrane
2. Which way do the molecules
move?
– If molecules move from higher
concentration to lower concentration, it is
diffusion
– If molecules move from lower
concentration to higher concentration, it
is active transport.

18. Moving Across a Membrane
Osmosis Diffusion Active
What
moves
Energy
Toward
which
side?
Example

19. Moving Across a Membrane
Osmosis Diffusion Active
What
Water Molecules Molecules
moves
Energy
Toward
which
side?
Example

20. Moving Across a Membrane
Osmosis Diffusion Active
What
Water Molecules Molecules
moves
Energy No No Yes
Toward
which
side?
Example

21. Moving Across a Membrane
Osmosis Diffusion Active
What
Water Molecules Molecules
moves
Energy No No Yes
Toward Water moves Molecules Molecules
to the side with move to less move to more
which more concentrated concentrated
side? molecules side side
Example

22. Moving Across a Membrane
Osmosis Diffusion Active
What
Water Molecules Molecules
moves
Energy No No Yes
Toward Water moves Molecules Molecules
to the side with move to less move to more
which more concentrated concentrated
side? molecules side side
Cell in a
Smell of
Example hypertonic
perfume
Na++/K+ pump
solution

23. Wrap-Up
 If a cell that contains a 10% salt solution is
placed in a 90% salt solution, will water flow
into or out of the cell? Is the cell hypertonic or
hypotonic?
 Identify the description as osmosis, diffusion, or
active transport?
1. Water moves into a cell from high concentration to
low concentration
2. Iodine molecules move into a cell from high
concentration to low concentration
3. Sodium molecules are moved from a low
concentration to a high concentration