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Just like you , early investigators had lots of questions about the structure and chemical composition of the cell membrane and how these properties could account for differences in the membrane's permeability to different type of molecules.

At least one of these researchers, Ernest Overton of the University of Zurich, realized that systematic differences in the permeability of the membrane to solutes that varied in size, charge and lipid solubility (how well they dissolved in lipids relative to water) could provide insight into the membrane’s biochemical composition. That is, information about the membrane’s permeability to molecules of varied chemical properties could reveal biochemical properties of the biological molecules forming the membrane itself.

After investigating the permeability of a large variety of cell types to hundreds of different compounds, Overton eventually deduced the general chemical properties of the cell membrane and from this correctly predicted the type of biological molecule from which the membrane must be primarily formed (De Weer, 2000)! Interestingly, and as so often happens in science, Overton’s original research question had nothing to do with investigating properties of the cell membrane. Rather his pursuit of this question bloomed from research on heredity for which he needed a traceable material that would pass through the plant cell membrane (Eichman, 2007).

Unfortunately, Overton never published the detailed results of these studies so his data are no longer with us (De Weer, 2000). Data similar to Overton’s do exist, however, and an example taken from a paper published in 1937 based on work conducted on alga cells is presented in figure below.

Relationship between the permeability (log cm/hr) of the plasma membrane of cells of the alga Chara ceratophylla to non-ionic, organic solutes and the solute’s a) size as indicated by the relative size of the bubble (molecular mass; grams/mole); the larger the bubble the larger the solute and b) solubility in oil relative to water (log). Low values of oil to water solubility (ex. 0.001) indicate virtually no solubility in lipids and very high solubility in water. Increasing values indicate an increasing solubility in oil relative to water. Data from Collander (1937).

What do these data suggest to you about the biochemical properties of the cell membrane and, in turn, the type of biological molecule from which the cell membrane is constructed? To answer this question, review the figure above and work through the questions below.

1. a. Carefully review the figure legend, axes labels and the data presented. In a sentence or two, describe what relationship, if any, there is between membrane permeability and the oil to water solubility of a solute.

2. Describe what relationship, if any, there is between cell permeability and solute size. To answer this question, work through the series of questions below.

  • a) On a piece of paper, sketch what the above figure is expected to look like if permeability increases with increasing solute size. (Assume the relationship between permeability and solubility is the same as above.)
  • b) On a piece of paper, sketch what the above figure is expected to look like if permeability decreases with increasing solute size. (Assume the relationship between permeability and solubility is the same as above.)
  • c) Does the actual relationship between permeability and solute size match either hypothesis you sketched in response to parts a and b? Please explain.
  • d) What do the data presented in figure 1 and your answer to part c suggest about the relationship between cell permeability and solute size? Please explain in a sentence or two.

3. Consider what you know about hydrophobic and hydrophilic molecular interactions together with the results you described in questions 1 and 2 above. What do these results collectively suggest, if anything, about the type of biological molecules that form the cell membrane (i.e. the biochemical composition)? Please explain how the data support your conclusion.

4. An undisturbed cell membrane is generally impermeable to ions. Does your description of the cell membrane from question 3 account for this? Please explain.

5. If your description of the cell membrane cannot account for the observation that undisturbed cell membranes are generally impermeable to ions, please amend it so that it does.

6. Early on scientists knew that water, a very small polar molecule, could diffuse across the membrane although this problem was ignored for many years. Can your description of the properties of the cell membrane the account for the cell membrane’s permeability to water? Yes or no? Please explain.

    Works cited

  • Collander, R. 1937. The permeability of plant protoplasts to non-electrolytes. Transactions of the Faraday Society. 33:985-990.
  • De Weer, P. 2000. A century of thinking about cell membranes. Annual Review of Physiology. 62:919-926.
  • Eichman, P. 2007. (External Link) . SHiPS Resource Center for Sociology, History and Philosophy in Science Teaching

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Discovering the structure of the plasma membrane. OpenStax CNX. Oct 15, 2007 Download for free at http://cnx.org/content/col10470/1.1
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