Полнотекстовый поиск:
Где искать:
только в названии
только в тексте
слова в тексте
только заголовок

Рекомендуем ознакомиться

Остальные работы->Реферат
England’s greatest poet and playwright was born in Stratford, the son of a tradesman and Alderman of Stratford, John Shakespeare in 1564. William, the...полностью>>
Остальные работы->Реферат
The premise of sin and redemption is evident in Samuel Taylor Coleridge’s famous ballad “The Rime of the Ancient Mariner”. The poem focuses on the tri...полностью>>
Остальные работы->Реферат
Laura Esquirel s, Like Water for Chocolate, is a modern day Romeo and Juliet filled with mouthwatering recipes. It has become a valued part of America...полностью>>
Остальные работы->Реферат
* * * * I blessed you far * * greater than I ever had before. * * But you were too busy * * to thank me once more. * * * * You didn’t feel sick * * be...полностью>>

Главная > Реферат >Остальные работы

Сохрани ссылку в одной из сетей:

History Of Cell Membrane Essay, Research Paper

In the early stages of the twentieth century, little was known about cell membranes. Until the early 1950s, the biological cell membrane was rarely mentioned in scientific literature. It was recognised that something was probably there, but hardly anything about it was known. Considering the lack of technical equipment available a century ago, scientists such as Charles Overton and Edwin Gorter were not only exploring new territory in looking at the properties of cell membranes, but laying the way for future cell biologists. Scientists had to wait another fifty years for the discovery of the electron microscope, let alone seventy years for the advent of freeze fracturing techniques.

Nageli and Cramer in 1855 had already suggested that biological cells are separated from their environment by a membrane possessing special characteristics, and in 1900 Overton performed some simple but classical experiments which proposed that cell membranes were composed of lipids (1). By measuring the permeability of various compounds across the membrane of a frog muscle, Overton found some interesting results. He observed that lipophilic molecules (molecules attracted to fat solvents) could easily cross this cell membrane, however larger lipid insoluble molecules could not. He also observed that small polar molecules could slowly cross the membrane. Other experiments with the likes of hen eggs suggested the presence of a lipid layer in the membrane. These results became known to biologists across the world and it was generally accepted that a semi-permeable lipid membrane surrounded some if not all cells (2).

Although this was opening new doors for cell biologists, the information was widely disregarded. One hundred years ago biological fact was based on what could be seen and since the proposed lipid membrane was smaller than the wavelength of visible light it could not be studied under the light microscope. Most biologists merely concerned themselves with more evident structures. However, some scientists continued to dedicate their time to examining this ?invisible? structure.

Two such biologists were the Dutch Edwin Gorter and F. Grendel. They recognised in 1925 that two such lipid layers existed. Whilst working on red blood cells they showed the first detailed analysis of structure based on a new model. They extracted the lipid from a red blood cell and spread it as a film on water. The area covered by the lipid turned out to be twice the surface area of the red blood cell. Gorter and Grendel thus concluded that in a cell membrane phospholipids must be arranged as a bilayer, i.e. two lipid molecules thick (4).

Загрузить файл

Похожие страницы:

  1. The Advent Of Penicillin Essay Research Paper

    Реферат >> Остальные работы
    ... Of Penicillin Essay, Research Paper The advent of penicillin forever changed the world of medicine ... in bacterial cell walls, and keeps the cell membrane structures from ... penicillin a storied history in biotechnology, the advent of new genetic engineering ...
  2. Cocaine The Super Drug Essay Research Paper

    Реферат >> Остальные работы
    ... Drug Essay, Research Paper This paper will be describing the history, celebrity use, effects, and research of ... General Office and the Pepsi Cola Company. Former drug abusers volunteered ... is absorbed through the mucus membrane into the bloodstream. In about ...
  3. Bacteria An Actual Report Essay Research Paper

    Реферат >> Остальные работы
    Bacteria An Actual Report Essay, Research Paper Bacteria comes from ... the plasma membrane there is a rigid cell wall that gives ... Cillates move by means of cilla which are like flagella ... All through history bacheria have shaped the developement of mankind. ...
  4. MARIJUANA The Controversial Drug Essay Research Paper

    Реферат >> Остальные работы
    ... Essay, Research Paper DESCRIPTION: Marijuana is a green, brown, or gray mixture of ... world since the beginning of written history. During this time ... and performing tasks that call for more than ... and produce inflammation of the mucus membranes, and also increases ...
  5. Sickle Cell Anemia Essay Research Paper By

    Реферат >> Остальные работы
    ... Brief History of Sickle Cell Disease Sickle Cell Disease in ... of deoxyHbS. Each of these effects reduces the number of ... cell membrane redundancy. This protects against sickling-induced stretching of the cell membrane ... first paper makes no mention of the patient ...

Хочу больше похожих работ...

Generated in 0.0023729801177979