Question

In the 1950s, J. D. Robertson reported that any membrane that he observed in the electron microscope looked the same. This led to his proposal of the Unit Membrane model of membrane structure suggesting that all membranes were exactly alike. Why was this model eventually rejected?

Answer 1

The Unit Membrane model was rejected due to new microscopy techniques showing diversity in membrane structure and function, leading to the adoption of the more comprehensive Fluid Mosaic Model, which accounts for membrane asymmetry and fluidity.

Step-by-step explanation:

The Unit Membrane model proposed by J.D. Robertson was eventually rejected because it could not explain the diversity in membrane function and structure revealed by newer scientific findings. With advances in microscopy, notably transmission electron microscopy (TEM), it became clear that although membranes have a common basic structure, they are not identical and have functional and structural differences.

The Fluid Mosaic Model, devised by S. J. Singer and Garth L. Nicolson in 1972, is currently accepted because it better explains both microscopic observations and the dynamic nature of the plasma membrane. This model describes the plasma membrane as a mosaic of components, such as phospholipids, cholesterol, proteins, and carbohydrates, that are fluid and can move in the plane of the membrane.

Additionally, the freeze-fracture technique showed the membrane asymmetry and further confirmed that the Unit Membrane model was too simplistic.