Transcript Transport In and Out of the Cella

Transport In and Out of the Cell
How Diffusion Works
• A little video
• Video
Diffusion
• This is also known as passive transport
and simple diffusion
• Passive transport is the movement of
molecules down a concentration gradient
from a region of higher concentration to
lower concentration.
• Passive transport NEVER requires energy.
(ATP)
• The steeper the gradient, the faster the rate of
diffusion.
• Humans obtain oxygen by simple diffusion
across moist membranes in the air sacs in our
lungs called alveoli.
Diffusion
• It is also affected by
– Temperature- the higher the temp. the faster
the molecules are moving
– Size of the Molecules- the bigger the
molecule is the harder it is to pass through the
membrane, possible not pass at all.
How Osmosis Works
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__how_osmosis_works
.html
Osmosis
• Osmosis- the diffusion of water (across a
membrane)
• Water will move in the direction where
there is a high concentration of solute (and
hence a lower concentration of water.
• Salt is a solute, when it is concentrated
inside or outside the cell, it will draw the
water in its direction. This is also why you
get thirsty after eating something salty.
SALT SUCKS
Isotonic Solution
• If the concentration of
solute (salt) is equal
on both sides, the
water will move back
in forth but it won't
have any result on the
overall amount of
water on either
side."ISO" means the
same
Hypotonic Solutions
• The word "HYPO" means
less, in this case there
are less solute (salt)
molecules outside the
cell, since salt sucks,
water will move into the
cell.
• The cell will gain water
and grow larger. In plant
cells, the central vacuoles
will fill and the plant
becomes stiff and rigid,
the cell wall keeps the
plant from bursting
Hypertonic Solutions
• The word "HYPER"
means more, in this case
there are more solute
(salt) molecules outside
the cell, which causes the
water to be sucked in that
direction.
• In plant cells, the central
vacuole loses water and
the cells shrink, causing
wilting.
Hypertonic Solution
• In animal cells, the cells also shrink
• This is why it is dangerous to drink sea
water - its a myth that drinking sea water
will cause you to go insane, but people
marooned at sea will speed up
dehydration (and death) by drinking sea
water.
How Facilitated Transport Works
• A little video to show you
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__how_facilitated_diffu
sion_works.html
Facilitated Diffusion
• Facilitated diffusion relies on special protein
channels to assist in transporting specific
substances across membranes.
Facilitated Diffusion
• The proteins helps or facilitated the
diffusion by changing shape and moving
the molecule down the concentration
gradient.
• This is very similar to diffusion in that both
involve the movement of molecules down
the concentration gradient with out energy
– They differ in the fact that this needs special
proteins (carrier proteins)
Dynamic Equilibrium
• When the rates of the forward and reverse
reactions are equal. The system is dynamic
because individual molecules react
continuously. It is at equilibrium because no net
change occurs.
All of the previous
require
NO ENERGY or
ATP
Active Transport
• This is the movement of molecules against
a gradient.
– This is like driving a car in traffic, going in the
wrong direction. It takes more energy to go
against the path then it does to go with the
traffic.
• This requires ENERGY, ATP.
Active Transport
• Active transport occurs with the aid of
carrier proteins, which are commonly
known as pumps.
• The cell maintains the proper balance of
substances it needs due to this active
transport.
• This helps maintain homeostasis.
Endocytosis
• This is the process by which a cell surrounds a
substance in the outside environment, enclosing
it in a portion of the plasma membrane.
• The membrane pinches off and leaves the
substance inside the cell and the resulting
vacuole, with the contents moves to the inside of
the cell.
• http://www.coolschool.ca/lor/BI12/unit4/U04L05/
endocytosis_final.html
Exocytosis
• This is the active release of molecules
from a cell. This is the opposite of
endocytosis.
• The cell uses this to get rid of wastes and
to secrete substances, for example
hormones, produced by the cell.
•
http://www.coolschool.ca/lor/BI12/unit4/U0
4L05/exocytosis.html
Pinocytosis
• This is also called cell drinking.
• This is the uptake of large dissolves
molecules.
• The plasma membrane surrounds
small/tiny particles and encloses them in a
vesicle.
• http://student.ccbcmd.edu/~gkaiser/biotuto
rials/eustruct/pinocyt.html
Phagocytosis
• This is the engulfing of large particles or
even small organisms by pseudopods.
• The cell membrane wraps around the
particles and encloses them forming a
vacuole.
• This is the way that the human white blood
cells take up bacteria.
• PAC-MAN
Receptor-Mediated Endocytosis
• This enables cells to take up large
amounts of very specific substances.
• The extra cellular substances bind to
specific on the cell membrane and are
brought into the cell.
– Example: This is the way that body draws the
cholesterol into the blood.
• Membrane pumps carry particles or ions
across the membranes AGAINST the
gradient (needs energy/ATP).
• The sodium-potassium pump is an
example of this
Sodium - Potassium Pumps
• This is one of the most common active transport
pumps.
• This is found in the plasma (cell) membrane of
animal cells.
• This maintains the levels of Sodium (Na) and
Potassium (K) in and out of the cell
• This protein pump uses the energy in order to
transport 3 sodium ions out of the cell while
moving 2 potassium ions into the cell.
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/
chapter2/animation__how_the_sodium_po
tassium_pump_works.html