Download Some things to consider before we start

Some things to consider before we start
Molecules in solids, liquids, and gases
are always moving.
In which state of matter are molecules
moving the fastest?
• Gas
Slowest?
• Solid
•
http://www.harcourtschool.com/activity/states_of_matter/
Some things to consider before we start
Substances must go through the cell
membrane in order to get in or out of
a cell.
Some things to consider before we start
• What substances need to go IN to a cell?
– Water, food/glucose/, oxygen
• What substances need to go OUT of a
cell?
– Wastes, carbon dioxide
• Cell Membrane Movie
CELL MEMBRANES
• … are selectively permeable, which means
that they allow some substances to pass
through but not others.
• Selective means “choosy” and
• Permeable means “to go through”
Demonstration: Smelly Balloons
Record your observations about the balloons’ smell as they are passed around.
Discussion Q’s:
1. How do the smells get out of the balloon?
2. How does your nose detect the smell?
3. Describe how the molecules are moving inside the
balloon?
4. How is the balloon similar or different to the cell
membrane?
Diffusion
• Molecules will always move from an
area where they are more
CONCENTRATED to an area where
they are less CONCENTRATED. This
is called diffusion.
What does concentrated mean?
• How many particles are packed in
an area
Diffusion continues until the
molecules of a substance are evenly
distributed in an area.
• This state of “evenly spread” is called
equilibrium.
• Do molecules stop moving once
equilibrium is reached?
• NO
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html
http://www.wisc-online.com/objects/index_tj.asp?objid=AP1903
Diffusion by Brainpop
… is a special kind of diffusion that is
very important to living things.
Osmosis is the diffusion of water
through a selectively permeable
membrane.
This is the manner in which water
gets into and out of cells.
Animation: How Osmosis Works
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html
• Water molecules will naturally flow
from an area in which the water
molecules are in greater numbers to
an area where they are in fewer
numbers.
http://www.biologycorner.com/bio1/diffusion.html
• Which way are water molecules
moving when a plant begins to wilt?
• Out of the cells
Passive transport
requires no ENERGY from the cell.
Diffusion and osmosis are examples of
passive transport.
Molecules in the cell membrane called
transport proteins help to move LARGER
molecules into or out of the cell. This still
does not require energy. Think of this as
being like taking a ferry ride without
having to pay. This is called Facilitated
transport
facilitated transport
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/ani
mation__how_facilitated_diffusion_works.html
Active transport
requires ENERGY and uses transport
proteins in the cell membrane.
Used when cells need to move substances
from areas of lower concentration to an area
of higher concentration. This is the opposite
of DIFFUSION and requires energy.
Other types of active transport
endocytosis
o Endocytosis occurs when VERY LARGE
THINGS need to move INTO a cell.
o A vesicle fuses to the cell membrane and
then releases an object into the cell.
o A white blood cell “eating” a BACTERIA
would be an example of endocytosis.
o What does “endo” mean? “IN”
Exocytosis
o Occurs when VERY LARGE molecules need
to move OUT of a cell.
o A vesicle fuses to the cell membrane and
then releases an object out of the cell.
o An example of exocytosis is when proteins
packaged by the GOLGI BODIES need to
move out of the cell, to get to another cell.
o What does “exo” mean? OUT OF
Let’s get some practice:
Tell if each of the following as diffusion, osmosis, facilitated
transport, active transport, endocytosis, or exocytosis.
• Large waste molecules stored in
vacuoles need to be moved out of a
cell:
• exocytosis
Water concentration outside a cell is
85%. Water concentration inside the
cell is 70%. Water flows into the cell:
• Osmosis
85%
70%
• You can smell the cookies baking in
the oven even before you enter the
kitchen:
• Diffusion
The concentration of Na ions outside
the cell is 10%. The concentration of
Na ions inside the cell is 25%. Na ions
move into the cell.
• Active Transport
25%
10%
A one-celled organism “eats” another
one-celled organism:
• Endocytosis
• Glucose molecules are helped to move
into the cell by transport proteins in
the cell membrane, but no energy is
used to do this:
• Facilitated transport