Diffusion, Osmosis and Active transport
Table of Contents
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1. Enzyme Notes
2. Enzyme lab pre & post questions (2 stamps)
3. Catalase lab data collection and rough draft
4. Notes on Enzyme Activity
5. Notes on Transport (p. 182-187) and class notes
6. Tape-In Cell membrane exploration.
7. Tape-In Keeping a balance
8. Tape-In Diffusion and Osmosis
9. Carrot Lab observations and data
10. Tape-In Solutions (Stamp)
11. Tape-In In –n- Out
12. Carrot Lab (4 stamps)
13. Osmosis Analysis Quiz (Stamp)
14. Rate “Per”fection page 1
15. Active Transport notes and WS (stamp)
Cellular Transport Unit
Passive Transport =
movement of substances
across the cell membrane
without any input of energy
by the cell
Passive Transport
Types
Diffusion = movement of molecules
from high to low [ ] (concentration)
- driven by the concentration gradient
- spreads out evenly till dynamic
equilibrium is reached
This Movement is the result of Kinetic
Energy of the molecules
Diffusion
2) Osmosis = diffusion of water
A solution may be one of the
following: (compared to a cell)
- isotonic solution: same [ ] of
water and solute
- hypotonic solution: lower [ ] of
solute, a lot of water
- hypertonic solution: higher [ ]
of solute, less water
Isotonic Solution (Red Blood Cells)
A solution is
isotonic to a cell
if it has the
same
concentration of
solutes as the
cell. Equal
amounts of
water enter and
exit the cell, so
its size stays
Hypotonic Solution (Red Blood Cells)
A hypotonic
solution has
fewer solutes
than a cell.
Overall, more
water enters a
cell in a
hypotonic
solution, causing
the cell to
expand and
Hypertonic Solution (Red Blood Cells)
A hypertonic
solution has
more solutes
than a cell.
Overall, more
water exits a
cell in a
hypertonic
solution, causing
the cell to shrivel
and even die
Direction of Osmosis
Outside the Cell
Water
Isotonic
Hypotonic
Hypertonic
Inside the Cell
Isotonic
Hypertonic
Hypotonic
Net Movement of
None
Inside the Cell
Outside the Cell
** If the solution outside the cell is hypotonic,
then inside the cell is hypertonic and vice versa
** Water tends to diffuse from hypotonic to
hypertonic
- Plasmolysis = cells shrink
when turgor pressure is lost
- the reason plants wilt
- Cytolysis = cell bursts due to
water entering the cell
How do freshwater organisms
deal with osmosis?

What would be the problem?
 Water would diffuse into the cells

What would organisms do to deal with
the problem?
 Pump water out or excrete large amounts of
water
How do marine organisms deal
with osmosis?

What would be the problem?
 Water would diffuse out of the cells

What would organisms do to deal with
the problem?
 Pump water in or excrete large amounts of
salt into their tissues
How do they do this?
Contractile Vacuole!
Full
Empty
Contractile Vacuole in action
3) Facilitated Diffusion
= move molecules across the
cell membrane through
carrier/transport proteins
- are specific for the type of
molecule they help diffuse
Facilitated Diffusion (Open Channels)
Facilitated Diffusion
(Proteins Change Shape)
Diffusion vs. Facilitated
Diffusion
Diffusion
Facilitated Diffusion
Overview

Passive Transport
 Diffusion
 Osmosis
 Facilitated Diffusion

Active Transport
 Protein Pump
 Bulk Transport
○ Endocytosis
 Pinocytosis
 Phagocytosis
○ Exocytosis
Active Transport =
substances can cross the cell
membrane with an input of
energy from the cell
The movement of molecules is
AGAINST the concentration
gradient. ( From low
concentration to high
concentration)
Active Transport
1) Endocytosis = the process by
which cells ingest “stuff”
- vesicle holds the “stuff”
- two types:
1) pinocytosis - solutes and fluids
2) phagocytosis - large particles
or whole cells
Endocytosis
2) Exocytosis = the process by
which cells release “stuff”
- is essentially the reverse of
endocytosis
Exocytosis
ACTIVE TRANSPORT – requires
energy input (ATP)
Protein Pumps
 Bulk Transport
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 Endocytosis – two types: phagocytosis and
pinocytosis
 Exocytosis
 Animation
 Another animation
HOMEOSTASIS AND TRANSPORT
I. Cell Membranes
A. Cell membranes help organisms maintain
homeostasis by controlling what
substances may enter or leave cells
B. Some substances can cross the cell
membrane without any input of energy by
the cell
C. The movement of such substances across
the membrane is known as passive
transport
D. To stay alive, a cell must exchange materials
such as food, water, & wastes with its
environment
E. These materials must cross the cell or
plasma membrane
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F. Small molecules like water, oxygen, &
carbon dioxide can move in and out freely
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G. Large molecules like proteins &
carbohydrates cannot move easily across the
plasma membrane
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H. The Cell Membrane is semipermeable or
selectively permeable only allowing certain
molecules to pass through
II. Diffusion
A. Diffusion is the movement of molecules
from an area of higher concentration to an
area of lower concentration
http://www.biosci.ohiou.edu/introbioslab/Bi
os170/diffusion/Diffusion.html
B. Small molecules can pass through the cell
membrane by a process called diffusion
C. Diffusion across a membrane is a type of
passive transport because it does not
require energy
D. This difference in the concentration of
molecules across a membrane is called a
concentration gradient
E. Kinetic energy keeps molecules in constant
motion causing the molecules to move
randomly away from each other in a liquid or
a gas
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The rate of diffusion depends on
temperature, size of the molecules, & type
of molecules diffusing
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H. Molecules diffuse faster at higher
temperatures than at lower temperatures
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I. Smaller molecules diffuse faster than
larger molecules
J. Most short-distance transport of materials
in and out of cells occurs by diffusion
 K. Solutions have two parts --- the solute
which is being dissolved in the solvent
 L. Water serves as the main solvent in living
things
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M. Diffusion always occurs down a
concentration gradient (water moves from
an area where it is more concentrated to an
area where it is less concentrated)
http://www.tvdsb.on.ca/westmin/science/sbi3a1
/Cells/Osmosis.htm
N. Diffusion continues until the concentration
of the molecules is the same on both sides
of a membrane
O. When a concentration gradient no longer
exists, equilibrium has been reached but
molecules will continue to move equally
back & forth across a membrane
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Ce
lls/Osmosis.htm
Osmosis
Think back to solutions:
solutes and solvents
 Osmosis is the process by which water
molecules diffuse across a cell membrane
from an area of lower solute concentration to
an area of higher solute concentration.
 Direction of movement depends on relative
concentrations of solutions.

Direction of movement into cells
 Hypotonic
to the cytosol
 solution outside the cell is less concentrated than inside the cell
 water moves into the cell
 Hypertonic
to the cytosol
 solution outside the cell is more concentrated than inside the cell
 water moves out of the cell
 Isotonic
 concentrations are equal
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
Red blood cells are placed into 3 different
types of solutions: figure out the types of
solution in the beakers by looking at the
RBC
ISOTONIC
HYPERTONIC
HYPOTONIC
How do freshwater organisms
deal with osmosis?

What would be the problem?
 Water would diffuse into the cells

What would organisms do to deal with
the problem?
 Pump water out or excrete large amounts of
water
How do marine organisms deal
with osmosis?

What would be the problem?
 Water would diffuse out of the cells

What would organisms do to deal with
the problem?
 Pump water in or excrete large amounts of
salt into their tissues
How do they do this?
Contractile Vacuole!
Finish the statements
Diffusion is…
 Osmosis is…
 A hypertonic solution has…
 A hypotonic solution has…
 A cell placed in a hypertonic solution will…
 A cell placed in a hypotonic solution will…
 Both osmosis and diffusion are _______
transport because they do not require
_______.

Passive Transport – no energy
input required
Diffusion
 Osmosis
 Facilitated Diffusion
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Carrot Lab Advice
Your goal is to experimentally find the
best isotonic solution for carrots.
 How? set up 4-5 baggies with carrots
and different concentrations of salt
solutions to leave over night.
 You will have to figure out what the
appropriate solutions should be and..
 how to properly make those solutions.
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Some Lab tips
Dab your carrot with a paper towel
before you weigh it so you are not
weighing the excess water.
 Be sure to use the electronic balance
appropriately otherwise you will get
incorrect data.
 Be meticulous about recording all
materials, procedures and data
collected.
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Using and electronic balance
http://youtu.be/wyHDFCVrsM8
Today: (Thu/Fri)
 Tape-In
and Check page 3/Procedures
 How good am I at writing procedures?
 Decide how much salt and how much
water you will put in each baggie
 Calculate the percent solution for each
baggie
 Revise carrot lab procedures
 Set up baggies and label
Hypothetical Carrot Lab Data
Percent Silinity
0%
0.25%
0.5%
0.75%
1%
0.35 g
0.16g
-0.02g
-0.26g
-0.40g
Change in
mass
Facilitated diffusion
Carrier Proteins: located in membrane
* Channels (always open)
* Gated channels (open when needed)
ACTIVE TRANSPORT – requires
energy input (ATP)
Protein Pumps
 Bulk Transport
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 Endocytosis – two types: phagocytosis and
pinocytosis
 Exocytosis
Active transport – Protein pumps