Transport in Cells
Biology 30 ~ Cells Unit
Mrs. S. Pipke-Painchaud
Cell Membrane

Cell Membrane Info:
– http://cellbio.utmb.edu/cellbio/membrane.h
tm
Cell Membrane

Fluid Mosaic Model
Fluid:
– Phospholipids move at 2 micrometres per second
– Proteins move at a much slower rate
Mosaic:
- Cell membrane is made up of many different
molecules
- Carrier proteins
- Phospholipids
- Glycoproteins
- Glycolipids
- Cholesterol
** Animation:
http://home.earthlink.net/~shalpine/anim/Life/memb.
htm

Fluid Mosaic
– http://www.bio.davidson.edu/people/macamp
bell/111/memb-swf/membranes.swf
– http://www.stolaf.edu/people/giannini/flashan
imat/lipids/membrane%20fluidity.swf
Molecules Crossing the Membrane

Can cross:
– Hydrocarbons and oxygen because they can dissolve
in the lipid bilayer
– Small polar molecules
 Water
 Carbon dioxide

Cannot Cross:
– Large polar molecules (Sugar)
– Ions (H+, Na+, Cl-)

Animation:
http://www.hillstrath.on.ca/moffatt/bio3a/cellbio
/celtrans3.htm
Review Topics

Cell Membrane – Fluid Mosaic
– http://www.stolaf.edu/people/giannini/flashan
imat/lipids/membrane%20fluidity.swf
General Info

Concentration = [ ] = the number of
molecules per volume.

Brownian Motion:
– Random movement (and collision of molecules) 
Think back to the collision theory of Science 10
– Molecules move in all directions with equal frequency
and bounce off of each other
– This causes molecules to spread out

Concentration Gradient:
– Is a regular concentration change over a
distance in a particular direction.
Wikipedia:
http://en.wi
kipedia.org/
wiki/Concen
tration_grad
ient
Passive Transport

Moving biochemicals and other particles
across membranes without the use of
energy.
Diffusion
Is the movement of molecules from an
area of high concentration to an area of
low concentration.
 Diffusion is affected by:

– Temperature
– Pressure (because molecules are forced to be
closer together)
– Concentration
** Diffusion increases as these variables do
Example . . .
Consider
perfume
diffusing
around a
classroom.
 TMSS
example:
Foods Class
cooking
cinnamon
buns

http://www.mun.ca/biology/Osmosis_Diffu
sion/tutor2.html
Example

General Anatomy and Physiology – Diffusion
Demo
– http://www.wisconline.com/objects/index_tj.asp?objID=AP1903

Interactive Animation:
– http://www.wiley.com/legacy/college/boyer/0470003
790/animations/membrane_transport/membrane_tran
sport.htm

Diffusion:
– http://www.stolaf.edu/people/giannini/flashanimat/tra
nsport/diffusion.swf
Diffusion . . .

Occurs until everything is equally distributed
– Equilibrium – a condition in which all acting forces are
balanced = stable condition

Example:
– As oxygen travels along in the blood until it reaches a
cell. In the bloodstream there is a high concentration
of oxygen and in the cell there is a low concentration
of oxygen so the molecule of oxygen diffuses from an
area of high concentration to an area of low
concentration.
– Carbon dioxide does the reverse and catches a ride
back to the lung to be exhaled.
Demos

Hot water and Cold water and red dye.
Facilitated Diffusion
Passive Transport
 Molecules diffuse across the cell membrane with
the help of carrier proteins.

– Protein carrier molecule speeds up the diffusion
process of substances already moving across the
membrane.
– Ex// sugars (polar molecules) and ions
– Movement is always down the concentration gradient

Facilitated Diffusion Animation
– http://www.d.umn.edu/~sdowning/Membrane
s/diffusionanimation.html

Animation:
– http://bio.winona.edu/berg/ANIMTNS/facdiff.
htm
Osmosis
The movement of water molecules from an area
of high concentration to an area of low
concentration
 Occurs through a selectively permeable
membrane.
 Water moves through the membrane to balance
the concentration

– Water follows the concentration gradient.

Process continues until the system is equal.
Osmosis

Osmosis Demo
– http://www.stolaf.edu/people/giannini/flashanimat/transport/os
mosis.swf

General Passive Transport Info
– http://www.biologycorner.com/bio1/diffusion.html#

Introduces Hyper/hypo/isotonic solutions
– http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.h
tm

Osmosis:
– http://www.colorado.edu/eeb/web_resources/osmosis/

Osmosis:
– http://ull.chemistry.uakron.edu/genobc/animations/osmosis.mov
Osmosis Demos
Plastic bag and Iodine demo
 Egg and vinegar and syrup

Active Transport
The transport of biochemicals and other
particles across a membrane.
 This process requires energy.


Animation
– http://www.brookscole.com/chemistry_d/tem
plates/student_resources/shared_resources/a
nimations/ion_pump/ionpump.html
Active Transport + Carrier Proteins






A molecule finds a specific carrier/transport
protein
The transport protein opens
Molecule moves inside
Transport protein opens to the inside
Molecule moves into the cell.
** the molecule is moving against the
concentration gradient so energy is required.
Active Transport
http://www.biologycorner.com/bio1/active
.html
 Active Transport (Carrier Proteins)

– http://www.northland.cc.mn.us/biology/Biolog
y1111/animations/active1.swf

Reviews both passive and active transport.
– http://www.northland.cc.mn.us/biology/Biolog
y1111/animations/active1.swf
Endocytosis
Cells engulf large particles by extending
cytoplasm around the particle
 As the membranes come together –
ingested particles are trapped in a pouch
(vesicle/ vacuole)
 Enzymes from the lysosomes are then
used to digest large molecules.

Endocytosis Websites

Max Animations:
– http://www.maxanim.com/physiology/Endocyt
osis%20and%20Exocytosis/Endocytosis%20a
nd%20Exocytosis.htm

http://www.sumanasinc.com/webcontent/
anisamples/molecularbiology/endocytosis.
html
Phagocytosis

Cells engulf solid particles
– Ex// white blood cells engulf bacteria

Phagocytosis
– http://student.ccbcmd.edu/~gkaiser/biotutori
als/eustruct/phagocyt.html
Pinocytosis

Cells engulf liquid droplets
– Ex// fats in the small intestine

Pinocytosis
– http://student.ccbcmd.edu/~gkaiser/biotutorials/eustr
uct/pinocyt.html

Diagram of both
– http://www.coolschool.ca/lor/BI12/unit4/U04L05.htm
Exocytosis
Process by which large molecules held
within the cell are transported to the
external environment
 Ex// release of waste products
 Small vesicles break off from the golgi
apparatus and move to the cell membrane
 Here they fuse with the cell membrane
and are released

Exocytosis

Exocytosis:
– http://academic.brooklyn.cuny.edu/biology/bi
o4fv/page/exocy.htm

Exocytosis:
– http://www.stanford.edu/group/Urchin/GIFS/
exocyt.gif

Endo/Exo Review
– http://www.stolaf.edu/people/giannini/flashan
imat/cellstructures/phagocitosis.swf
Review

Access
Excellence:
http://www.a
ccessexcellen
ce.org/RC/VL
/GG/ecb/com
parison_activ
e_passive_tr
ansport.html

Info from: Access Excellence
– http://www.accessexcellence.org/RC/VL/GG/ecb/comparison
_active_passive_transport.html

Solutes cross cell membranes by passive or active transport.
If uncharged solutes are small enough, they can move down their
concentration gradients directly across the lipid bilayer itself by
simple diffusion. Examples of such solutes are ethanol, carbon
dioxide, and oxygen. Most solutes, however, can cross the
membrane only if there is a membrane transport protein (a carrier
protein or a channel protein) to transfer them. As indicated, passive
transport, in the same direction as a concentration gradient, occurs
spontaneously, whereas transport against a concentration gradient
(active transport) requires an input of energy. Only carrier proteins
can carry out active transport, but both carrier proteins and channel
proteins can carry out passive transport.
Resources

Chart of Movement across the membrane:
– http://defiant.corban.edu/jjohnson/Pages/BioI/07/Traffic_Conce
ptMap.html

Listing of Bio Info
– http://science.nhmccd.edu/biol/bio1int.htm#biochem



http://www.northland.cc.mn.us/biology/Biology1111/ani
mations/active1.swf
http://www.stolaf.edu/people/giannini/biological%20ana
mations.html
http://defiant.corban.edu/jjohnson/Pages/BioI/07/Memb
rane.html