Davson and Danielli developed a model for the plasma membran

Davson and Danielli developed a model for the plasma membrane called the Sandwich Model (pictured below) with a phospholipid plasma membrane and proteins like bread slices on a sandwich on either side. Although appearing to be supported by TEM (right image) and accepted for several years it was shown to be inaccurate.

Explain why the sandwich model is impossible and how we know this. Be thorough in your answer. Freeze-fracture microscopy does not sufficiently answer this question.

Solution

Sandwitch model for plasma membrane is not possible because, if plasma membrane would had this configuration, it would not have had fluid nature and would have been static. Its fluidity could not be explained by taking this model into consideration. Moreover transportation of water and water soluble substance is diificult if plasma membrane have had this structure.