Download The Cell and Its Environment

The Cell in its Environment
6th Grade Text, Chapter 5-1
CELL MEMBRANE
“THE DOOR MAN”
• The cell membrane is
selectively permeable.
That is… it regulates which
materials can enter and leave
the cell.
• Examples:
– Permeable to water, oxygen,
and carbon dioxide
– Not permeable to large
molecules and salts
Image: www.answers.com/topic/semipermeable
What is SELECTIVE PERMEABILITY?
• Feature and a function of
the cell membrane essential
to maintain equilibrium by
regulating the passage of
some substances and not
others.
• Some substances can pass
through but other substances
cannot
cell transportation *
Substances can move in and
out of a cell in 2 ways:
1. Passive transport
•
•
diffusion
osmosis
2. Active transport
•
•
endocytosis
exocytosis
Passive transport *
A molecule that crosses the membrane by
moving down the gradient (with the gradient)
and does not require energy
• Diffusion
• Osmosis
DIFFUSION
• Process by which molecules move from an area of higher
concentration to an area of lower concentration.
• Concentration:
– The amount of a given substance in a given volume.
– Ex: How much sugar is in your glass of iced tea.
What causes diffusion?
• Over time the molecules will spread out
until they are evenly spread over an area
or reach equilibrium.
OSMOSIS
• Is a process in which the
water molecules moves from
an area of higher
concentration of water to an
area of lower concentration
of water
• The water molecules move
through a selectively
permeable membrane until
equilibrium has been reached
Is osmosis important
• Yes it is important because cells cannot
function properly without water!!!!!
Cell environment
Solutions and osmosis
solutions!
• a red blood cell is put in a glass of distilled
water (all water with no salt or sugar in it)
also known as hypotonic solution.
• 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. In
the end pieces of cell membrane are left in
the water.
http://www.usd.edu/~bgoodman/Osmos.htm
Solution= solute + solvent
• Solute
a substance dissolved
in another substance
NaCl
• Solvent
A liquid in which
substances are
dissolved
H 2O
solutions!
• Hypertonic
• solution that has more solutes than the
cytoplasm of the cell.
• If water molecules continue to diffuse out
of the cell, it will cause the cell to shrink.
Green Machine Elodea
• Distillated water
Hypotonic solution
• H2O + NaCl
• Hypertonic solution
Green Machine Elodea
• Distillated water
• NaCl Hypotonic
solution
• H2O + NaCl
• Hypertonic solution
DIFFUSION BP IN RED CELLS:
OXYGEN
• There are a lot more oxygen
molecules outside of the cell
than there are in the cell.
• That is, there is a higher
concentration of oxygen
molecules outside of the cell,
and a lower concentration of
oxygen molecules inside the
cell.
• This causes oxygen molecules
to move into the cell.
• Passive transport BP
Osmosis & Red Blood Cells
Distilled Water:
Salt Water:
Water moves into the
cell because there is
more salt in the cell
that there is water.
Water moves out of
the cell and into the
surroundings causing
the cell to shrink
Normal Red
Blood Cell
Image: http://academic.brooklyn.cuny.edu/biology/bio4fv/page
How does it works for unicellular
organism?
Questions:
• Which way will the oxygen molecules move?
Into the cell
• Why will the oxygen molecules move into the
cell?
• Because during diffusion the oxygen molecules
will move from an area of high concentration to
an area of low concentration.
Let’s fill out our diagram!
ACTIVE TRANSPORT *
• The movement of materials through a cell membrane using energy.
• This occurs when a cell needs to take in a substance that is higher
concentration inside the cell instead of outside the cell.
• The cell needs to move materials in the opposite direction as diffusion.
• Cells can do this but they have to use energy.
Active transportation
• Endocytosis
– Proteins in the cell membrane function to pick up
molecules that are needed inside using energy
TRANSPORT PROTEINS
• Proteins that are located in the cell membrane that “pick up”
molecules outside of the cell and bring them in.
• Process requires the cell to use energy.
Active transport
• Engulfing or phagocytosis
Cell membrane surrounds or
engulf a particle to bring it in to
the cell using energy
Once it is engulfed the cell
membrane connects and form
a vesicle or vacuole
Phagocytosis
• Paramecium eating
yeast
• Contractile vacuole
• Amoebas eating
paramecium
• More amoebas
Active transport
• Exocytosis
• the process by which a
cell packages materials
in membrane secretory
vesicles inside the cell
and directs them to fuse
with the cell membrane
releasing the packaged
materials to the exterior
space.
Active Transport BP
Question:
• How is active transport different
than diffusion?
 Diffusion:
high concentration ► low concentration
Does not require energy
 Active Transport:
low concentration ► high concentration
Requires energy
Why are cells so small?
• As cells grow, the amount of surface area becomes too large to
allow food and wastes to enter & leave the cell quickly enough
• If it grows too large it cannot function well enough to survive
• When a cell reaches a certain size it divides into two new cells.
• interactive video for active and pasive
transport
• interactive
• http://leavingbio.net/OSMOSIS%20AND%
20DIFFUSION.htm
• http://www.wisconline.com/Objects/ViewObject.aspx?ID=
AP1903
• http://www.wisconline.com/Objects/ViewObject.aspx?ID=
AP11403
• http://www.wisconline.com/Objects/ViewObject.aspx?ID=
• http://www.udel.edu/biology/ketcham/micr
oscope/testFLV8.html