Name: Introduction to Cells
Uploaded: 2019-07-19
Duration: 2 min 29 s
Description: Cells are the basic building blocks of all living things. They are made of water, inorganic ions, and carbon-containing molecules. Watch the video.

Question

Describe the experimentation that led to the proposal of the Davson-Danielli model of the cell membrane and its later falsification leading to the Singer-Nicolson model.

Accepted Answer

The cell membrane is made up of phospholipid, cholesterol, proteins, lipoproteins and glycoproteins. Cholesterol is also a component of animal cell membrane. Hugh Davson and James Danielli in 1935 proposed a model of the cell membrane called the Davson–Danielli model or sandwich model based on the evidence from electron microscopy. They observed two dark parallel lines with a light region in between in the electron micrograph. This model described that a phospholipid bilayer that lies between two layers of proteins. It was the first model that describes the position of proteins within the lipid bilayer found in membranes. The model was also called a ‘lipoprotein sandwich’, as the lipid bilayer was sandwiched between two protein layers.

The Davson–Danielli model predominated until the fluid mosaic model of Singer and Nicolson advanced in 1972. The fluid mosaic model expanded on the Davson–Danielli model by including transmembrane proteins and eliminated the previously proposed flanking protein layers that were not supported by experimental evidence.

Describe the experimentation that led to the proposal of the Davson-Danielli model of the cell membrane and its later falsification leading to the Singer-Nicolson model.

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