Question

In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?

A) The membrane is only fluid across a very narrow temperature range.
B) Proteins rarely move, even though they possibly can do so.
C) Unsaturated lipids are excluded from the membranes.
D) The concentration of protein molecules is now known to be much higher.
E) The proteins are known to be made of only acidic amino acids.

Answer 1

The Fluid Mosaic Model has been refined to reflect a higher concentration of protein molecules in the cell membrane, supporting its complexity and dynamic nature in facilitating cellular processes.

Step-by-step explanation:

In the years since the proposal of the Fluid Mosaic Model of the cell membrane by S.J. Singer and G.L. Nicolson, one of the important observations that has been added to the model is that the concentration of protein molecules within the cell membrane is now known to be much higher. This refinement acknowledges the complex and abundant nature of membrane proteins in facilitating various cellular processes, including transport and signal reception. Therefore, the correct answer to the question is: D) The concentration of protein molecules is now known to be much higher.

The Fluid Mosaic Model has also been refined over time to account for the dynamic nature of membrane proteins and lipids, which are understood to be in constant motion, making the membrane a fluid structure rather than static. Furthermore, the presence of various kinds of lipids, such as unsaturated fatty acids with kinks, contributes to the fluidity of the membrane by preventing the fatty acid tails from packing tightly together.