Passive and Active TransportUnit 2- Cell Structure and Function
Outcomes:• Identify the factors
which influence the rate and direction of diffusion.
• Identify how osmosis is related to diffusion and the value of osmosis to living organisms.
• Examine the mechanisms of active transport by identifying and explaining the two processes.
• Compare the similarities and differences between active and passive transport.
**Don’t have to write these out**
Cellular Transport Cellular transport moves substances
within the cell and moves substances into and out of the cell
There are 2 types:1. Passive Transport2. Active Transport
Passive Transport These types of transport do not require
energy a) Diffusionb) Facilitated Diffusionc) Osmosis
A) Diffusion Remember from years before that
particles in solids, liquids, and gasses are in constant random motion (Particle Theory of Matter)
Substances dissolved in water move constantly in random motion
The random motion of these particles creates DIFFUSION
The amount of a substance in a certain area is called CONCENTRATION
Substances diffuse from an area of higher concentration to an area of lower concentration
Watch the following video and draw the diagram on the next page: http://
www.youtube.com/watch?v=Um6OoN81rb4
Diagram of Diffusion
Diffusion occurs until there is an equal concentration of particles in an area/cell
The particles continue to move randomly, but there is no overall change- this is called DYNAMIC EQUILIBRIUM
Rate of Diffusion 3 main factors affect the rate that
diffusion occurs1. Concentration
When concentration is high, diffusion happens quickly because there are more particles to collide with each other
2. Temperature When temperature increases, the particles
collide more quickly3. Pressure
When pressure increases, the particles collide more quickly
B) Facilitated Diffusion While water can diffuse readily across a
plasma membrane, most other substances need help
Happens through carrier and channel proteins
The CHANNEL PROTEINS in the plasma membrane of the cell are used to diffuse ions and small molecules across the cell membrane (draw the diagram below)
http://kentsimmons.uwinnipeg.ca/cm1504/Image132.gif
CARRIER PROTEINS are also used to move substances across a cell membrane by changing shape to help diffusion in a cell (Draw the diagram)
http://www.biologycorner.com/resources/simpdiff.jpg
C) Osmosis The diffusion of water across a
selectively permeable membrane is OSMOSIS
Regulating the movement of water across the plasma membrane is an important factor in maintaining homeostasis
(draw the next diagram)
http://www.biologycorner.com/resources/osmosis.jpg
If the concentration of solute is higher on one side of the cell membrane, the water will move towards the higher solute concentration
This diffusion happens until dynamic equilibrium occurs
Isotonic Solution When a cell is in a solution that has the
same concentration of water and solutes is said to be in an ISOTONIC solution
Water moves into and out of the cell at the same rate and cells keep their normal shape
Hypotonic Solution If a cell is in a solution that has a lower
concentration of solute, the cell is said to be in a HYPOTONIC solution
There is more water outside of the cell than inside the cell which causes water to move into the cell
The water moving into the cell creates osmotic pressure
In an animal cell, the water may enter the cell so much so that it bursts
A plant cell will not burst if there is a high osmotic pressure because the cell wall is very rigid
Hypertonic Solution When the concentration of the solute
outside of the cell is higher than inside Water moves outside the cell Animal cells may shrivel because of
water loss Plant cells wilt because the water
vacuole is empty
Draw the diagram:
http://4.bp.blogspot.com/-yiAZAMJRq4s/Ta79K3vVk8I/AAAAAAAAACE/MhfD0z_ABi8/s1600/hypo.jpg
Video Explanation http://
www.youtube.com/watch?v=AYNwynwaALo
Active Transport This happens when substances have to
move from an area of lower concentration to an area of higher concentration
This process makes sure that cells have the proper amount of substances inside of them
These forms of cellular transport REQUIRE the use of ENERGY by the cell
a) Pumps (carrier proteins)b) Endocytosis/Exocytosis
A) Pumps (Carrier Proteins) Carrier proteins can move substances
against a concentration gradient Some pumps move one type of
substance in one direction across the plasma membrane
Other pumps move two substances in both directions across the plasma membrane
Sodium Potassium Pump This is a common type of pump moves 3 sodium ions out of the cell moves 2 potassium ions into the cell ATP (a form of energy) breaks down into
ADP to do this Video demonstration
http://www.youtube.com/watch?v=Q73uJ8WlY_E
http://4.bp.blogspot.com/_207DNIaL-gc/TOaSu8u3q7I/AAAAAAAAAV4/9QLnFO82wQA/s1600/07_16SodiumPotassiumPump.jpg
B) Endocytosis & Exocytosis Particles that are too large to travel
through the plasma membrane leave or enter the cell differently
Endocytosis ENDOCYTOSIS is when a cell surrounds
something outside of the cell The cell membrane pinches off and
leaves the substance inside the cell The substance is now in a vesicle to
travel throughout the cell
Exocytosis Is when substances leave the cell by
vesicles joining the plasma membrane to expel the substance
http://www.kscience.co.uk/as/module1/pictures/endoexo.jpg
