Weekly Announcements
 Chapter
7 Test Friday 10/4/13
9/30/13
Diffusion & Osmosis
Types of transport in Cells
Passive transport - movement of
substances through a membrane
from a region of high to a region of
low concentration - no energy
needed (ATP) - diffusion and
osmosis are examples of this
 Active transport - movement of
substances through a membrane
from a region of low concentration
to a region of high concentration requires cellular energy (ATP)

Whether passive or active
transport is needed depends on
the CONCENTRATION GRADIENT
 The concentration gradient is the
difference in the concentration of
a substance in two different
spaces
 Concentration - the amount of a
particular substance in a
contained area compared with
the amount of the same
substance in another area
 Translation: Amount of

PROCESSES OF THE PLASMA
MEMBRANE
There are two types of passive
transport: Diffusion and
Osmosis
 The goal of both diffusion and
osmosis is to reach
EQUILIBRIUM within the cell
 Equilibrium is a condition in
which the movement in one
direction is equal to the
movement in another direction

Diffusion
the tendency of molecules to move
from an area of higher concentration
to an area of lower concentration
 (concentration gradient- diff in conc.
between 2 regions)

Osmosis





movement of water through a membrane
from a region of higher to lower con.
Solute - substance being dissolved in a
liquid (ex. salt)
Solvent - substance doing the dissolving
(ex. water)
Permeability - the extent to which a
membrane will allow particular sized
molecules to pass
Semi-permeable membrane (selectively
permeable)-allows some molecules to pass
but not others

So, describe how “Kool-Aid”® is
made with regard to the terms
“solute” and “solvent”. What is the
“universal solvent”?




When comparing two solutions there are
three possible relationships, We Identify
the relationships by determining what
would happen if a cell were placed in the
solution.
Hypertonic- A solution that causes a
cell to shrink because of osmosis.
Meaning water leaves the cell.
Hypotonic- A solution that causes a cell
to swell because of osmosis meaning
water rushes into the cell.
Isotonic-A solution that causes no
change in cell size. Meaning there is no
movement of water.
If the fluid outside
the cell has…
…less water than is
present inside the cell
…more water than is
present inside the cell
…same amount of
water as inside the cell
Then the outside
fluid is…
Water moves…
Effect on the cell?

So, answer this question…. Why do
“establishments” offer free popcorn,
peanuts, and pretzels to their
patrons if they are serving
beverages? What changes are
taking place in the body to initiate
the need for more beverages?
10/1/13
 Do
Now: Name the two types of
passive transport and describe how
they are different from each other.
 HW:
Read pages 212 – 213 and
complete the questions in the 7.3
Assessment
Active Transportthe movement of a substance
against the concentration gradient.
(uphill)
 Active transport requires cell to USE
ENERGY





Sodium pump - transports three
sodium ions out of the cell and
two potassium ions into the cell
Both are against the
concentration gradient
The energy needed to perform
this activity is supplied by ATP
(adenosine tri-phosphate)
ATP is a unit of energy made by
the cell




Endocytosis- the movement of a
substance into the cell by a vesicle. A
vesicle is a form of packaging that is
used by cells.
Exocytosis- the movement of a
substance out of the cell by a vesicle.
Phagocytosis- cytoplasm of cell
surrounds and engulfs particle--ex.
ameba and white blood cell
Pinocytosis- plasma membrane
"pinches in" to permit entry of molecules
too large to diffuse through
Passive Vs. Active Transport
Writing Activity
 Compare
the two types of transport
in no more than 2 paragraphs (3-4
sentences each paragraph). Make
sure to describe in detail the
differences between both types of
transport.
Diffusion
The movement of molecules
from an area in which they
are highly concentrated to an
area in which they are less
concentrated.
Diffusion
Osmosis
 The
diffusion of water across a
selectively permeable membrane.
 Osmosis
is a type of Passive
Transport.
 Osmosis
requires NO ENERGY.
Osmosis



Hypertonic- a
solution that causes a
cell to shrink because
of Osmosis.
Hypotonic- a solution
that causes a cell to
swell because of
Osmosis.
Isotonic- a solution
that causes no change
in the size of the cell
Osmosis

In this picture a red
blood cell is put in a
glass of distilled
water. Because there
is a higher
concentration of water
outside the cell, water
enters the cell by
OSMOSIS. In this
case too much water
enters and the cell
swells to the point of
bursting open.
Selectively Permeable
A
membrane that allows only certain
materials to cross it
 Materials pass through pores in the
membrane
Summary
Diffusion is the movement of molecules
from an area of higher concentration to an
area of lesser concentration.
 Osmosis is the movement of water thru
a semi permeable membrane.
 Active transport requires energy.
(molecules move from an area of lesser to
higher concentration)
 Passive transport needs NO ENERGY!
(molecules move from an area of higher to
lesser concentration).

Why are osmosis & diffusion
important?
All living things have certain requirements
they must satisfy in order to remain alive
– maintain homeostasis
 These include exchanging gases (usually
CO2 and O2), taking in water, minerals,
and food, and eliminating wastes.
 These tasks happen at the cellular level.
 Molecules move through the cell
membrane by diffusion
 A balance, or EQUILIBRIUM, must be
maintained.

10/2/13
 Do
Now: What is homeostasis and
how do cells maintain it?
 HW:
Review 7.4
– Chapter 7 Test Friday
10/3/13
 Do
Now: Clear your desks! Today is
your review day for tomorrow’s
chapter 7 test.
 HW:
Study for Chapter 7 Test
tomorrow
10/4/13
 Do
Now: Clear your desks! Today is
your Chapter 7 Test!