Transcript 7-3 Cell Transport - MrKanesSciencePage

7-3 Cell Transport
REVIEW
Regulates what enters and
leaves the cell
Protects and supports the
cell
Composed of
Lipids = bilayer
Proteins = channels
Carbs = identification
cards
Different types of movement
• Passive Transport
– Diffusion
– Osmosis
– Facilitated Diffusion
• Active Transport
– Membrane Pumps
– Endo/Exocytosis
1.
PASSIVE TRANSPORT – Diffusion
“passive” = no energy required
–
Molecules in Motion
•
•
•
Molecules are in constant motion
Move from a region where they are more
numerous (high concentration) to where
they are less numerous (low concentration)
Want to reach a state where molecules are
spread out evenly = EQUILIBRIUM
1.
PASSIVE TRANSPORT – Diffusion
“passive” = no energy required
– Diffusion – the process by which molecules of a substance
move from areas of higher concentration of that substance
to areas of lower concentration
– Factors that contribute to movement of substances:
• Unequal concentrations
• Permeability
– The cell membrane is selectively permeable – allowing some
things to cross while others cannot
2. PASSIVE TRANSPORT - Osmosis
–
Most molecules cannot
dissolve in the lipid
bilayer of the cell;
therefore, they cannot
pass through - BUT –
WATER CAN…
–
Osmosis – diffusion of
water across a
selectively permeable
membrane
–
Water will pass through
the membrane from a
area of high water
concentration to an area
of low water
concentration
–
There is a net movement
of water from where
there is less solute to
where there is more
solute (in an attempt to
dilute it)
–
Osmotic pressure – the
force exerted by osmosis
•
Types of tonicity (the
ability of a substance to
draw water towards it)
Isotonic Solution
 “Iso” = the same
 Water will move both
ways in equal amounts
 Why is important that
contact lens solution is
isotonic?
Hypotonic Solution
 "Hypo" = less
 Less solute (salt) molecules outside
the cell
 Water will move in both directions
 BUT more water will move into the
cell causing it to grow larger
(cytolysis)
 In plant cells, the central vacuoles
will fill and the plant becomes stiff
and rigid (turgid), the cell wall keeps
the plant from bursting
 In animal cells, the cell may be in
danger of bursting, organelles called
CONTRACTILE VACUOLES (only on
paramecium) will pump water out of
the cell to prevent this
Hypertonic Solution
 "Hyper" = more
 More solute (salt) molecules outside
the cell
 Water will move in both directions
 BUT more will move out of the cell
causing it to shrink (plasmolysis)
 In plant cells, the central vacuole
loses water and the cells shrink,
causing wilting (loss of turgor
pressure)
 In animal cells, the cells shrink
 In both cases, the cell may die
 Why is it dangerous to drink sea
water?
 This is also why "salting fields" was a
common tactic during war, it would
kill the crops in the field, thus
causing food shortages
Which type of solution is it?
A
B
C
1. What type of solution
is this “cell” in?
a: hypotonic solution
2. What will happen to
this “cell” over time?
a: the cell will
expand and possibly
burst = CYTOLYSIS
3. PASSIVE TRANSPORT - Facilitated Diffusion
–
–
–
No energy required
Carrier proteins
transport molecules
across the membrane
(from high to low
concentrations)
Molecules may be too
big or cells may need
to get the molecules
quickly
4. ACTIVE TRANSPORT
–
–
Requires energy (usually ATP)
Move molecules against the concentration
gradient – the opposite direction of passive
transport
4. ACTIVE TRANSPORT - Membrane Pumps
–
–
–
Transport macromolecules move molecules across
the cell membrane
Requires ENERGY
Examples – calcium, potassium, sodium ions
5. ACTIVE TRANSPORT –
Endocytosis vs. Exocytosis
•
–
–
–
Endocytosis – taking materials into the cell by
infoldings of the cell membrane
Phagocytosis – when large particles (food, microorganisms)
are taken into the cell
Pinocytosis – when liquids or relatively small particles
(solutes) are taken into the cell
Receptor-mediated endocytosis
• Exocytosis – when large molecules
are removed from the cell
– Contractile vacuoles – water is pumped
out of the cell so it doesn’t burst
active
transport
concentration
gradient
facilitated
diffusion
particles/
water
energy