Essential Question:
How does a cell both protect itself
from hazards in its environment
and allow resources from that
environment in to carry out lifesustaining functions?
INB Pg. 35
A. The cell membrane undergoes SELECTIVE
PERMEABILITY
- Allowing only certain substances in & out
of the cell. (due to molecule size & polarity)
B. Cell Membrane structure
1. comprised of a lipid bilayer (2 layers)
a. lipids (fats) are compounds that are insoluble in water.
b. lipids have two ends:
1). Polar Head end, “loves water” (hydrophilic)
2). Nonpolar 2 tail ends, “fear water” (hydrophobic)
c. bilayer arrangement: (lets draw it)
C. How does nutrients get in & waste get out…
1. Simple diffusion: small/nonpolar molecules pass
through the cell membrane using a concentration gradient.
a. Concentration gradient= one side of the membrane
contains an area with a higher # of particles & the other side has
a lower # of particles.
b. particles move from an area of higher
concentration to an area of low concentration = HOMEOSTASIS
(balance)
2. Osmosis: simple diffusion of WATER across
a cell membrane
Big Idea: large molecules cannot diffuse (fit) across
the membrane, so water moves to achieve homeostasis
http://highered.mheducation.com/sites/007249585
5/student_view0/chapter2/animation__how_osmo
sis_works.html
Let’s go back to our
Cell Transport Model
HW: Analysis Questions
-Answer these questions directly under your cell transport notes.
1. Why does this arrangement allow for molecules with
one hydrophobic end and one hydrophilic end to exist
in an environment that has water on both sides?
2. Explain the science behind
this the slug cartoon. Include a
labeled drawing in your
explanation.
a. Osmotic Solutions
1. Hypotonic- contains low amount of solute
compared to the solution on the other side of the
membrane.
*cell placed in a hypotonic solution = swelling &
bursting. Plant cells don’t burst because of cell wall.
Don’t put me in a lake!!
a. Osmotic Solutions
2. Hypertonic- contains a high amount of
solute compared to the solution on the other side of
the membrane.
*cell placed in hypertonic solution = shriveling
a. Osmotic Solutions
3. Isotonic- concentration of solutes is equal
on both sides.
*water moves in & out at even rate.
3. Facilitated diffusion- larger molecules
(sugar) that cannot fit through the
membrane use a Protein channel.
4. Active Transport- moving substances
AGAINST the concentration gradient (from
low to high)
a. Protein Pumps- proteins across the
membrane send molecules from low to high
concentration.
Ex: Body cells must pump carbon
dioxide out into the surrounding
blood vessels to be carried to the
lungs for exhale. Blood vessels
are high in carbon dioxide
compared to the cells, so energy
is required to move the carbon
dioxide across the cell membrane
from LOW to HIGH
concentration.
b. Endocytosis- moving bulk
material INTO the cell through fusing
with the cell membrane.
c. Exocytosis- moving bulk
materials OUT of the cell
Types of Cellular Transport
•
1. Diffusion
2. Facilitated Diffusion
3. Osmosis
•
Weeee!!!
Passive Transport
cell doesn’t use energy
high
low
Active Transport
cell does use energy
1. Protein Pumps
2. Endocytosis
3. Exocytosis
This is
gonna be
hard
work!!
high
https://www.youtube.com/watch?v=Ptmlvtei8hw
low
Processing Point
-Complete this task directly under your notes on Pg. 36 or 37
5 word Summaries:
-Use ONLY five words to describe the following cell
transport terms.
*Diffusion
*Osmosis
*Facilitated diffusion
*Endocytosis
*Exocytosis
*Protein pumps