Gorter and Grendel's Lipid Bilayer Discovery Year

The question asks about the year when E. Gorter and F. Grendel made their significant breakthrough regarding the structure of the cell membrane, specifically concluding it was a lipid bilayer based on surface area measurements of lipids.

E. Gorter and F. Grendel conducted experiments using lipids extracted from red blood cells. They carefully measured the surface area that these lipids occupied when spread as a single layer (monolayer) on a water surface. They then compared this measured area to the estimated surface area of the original red blood cells from which the lipids were extracted.

Their key observation was that the area occupied by the lipid monolayer was approximately double the calculated surface area of the red blood cells. This led them to propose a model for the cell membrane where the lipids are arranged in two layers, or a bilayer, around the cell. This bilayer structure would effectively double the lipid surface area compared to a single layer covering the same cell area.

This groundbreaking work was a crucial step in understanding the molecular architecture of the cell membrane.

Based on historical accounts and biological literature, the year this pivotal research by E. Gorter and F. Grendel was published, proposing the lipid bilayer model based on their surface area measurements, was 1925.

Let's look at the options provided:

• 1962: This year is associated with the fluid mosaic model proposed by Singer and Nicolson, which built upon the lipid bilayer concept but is much later than Gorter and Grendel's initial work.
• 1945: This year does not correspond to Gorter and Grendel's specific lipid bilayer hypothesis.
• 1910: This year is too early for Gorter and Grendel's detailed lipid studies on cell membranes.
• 1925: This year aligns with the publication date of Gorter and Grendel's influential paper proposing the lipid bilayer structure of the cell membrane based on their experiments.

Therefore, the year E. Gorter and F. Grendel made their breakthrough concerning the lipid bilayer structure of cell membranes was 1925.

Understanding Gorter and Grendel's Experiment

Gorter and Grendel's approach was ingenious for its time:

• They obtained a known quantity of red blood cells.
• They extracted lipids from these cells.
• They spread the extracted lipids on a Langmuir trough, a device used to measure the area occupied by a monolayer on a liquid surface.
• They determined the maximum area the lipids would cover as a single molecular layer.
• They estimated the total surface area of the red blood cells they started with.
• Comparing these two areas (lipid monolayer area vs. cell surface area), they found the lipid area was roughly twice the cell area.
• This ratio strongly suggested that the cell membrane was composed of two layers of lipids.

Revision Table: Key Cell Membrane Models

Additional Information: The Significance of the Lipid Bilayer

The concept of the lipid bilayer is fundamental to cell biology. Here's why it's so important:

• Barrier Function: The hydrophobic tails of the lipids face inwards, creating a non-polar core that acts as a barrier to most water-soluble molecules. This allows cells to maintain distinct internal environments.
• Fluidity: The lipids and many proteins within the bilayer are able to move laterally, giving the membrane a fluid-like quality. This fluidity is essential for various membrane functions like protein diffusion, cell movement, and cell division.
• Selective Permeability: While the bilayer acts as a general barrier, embedded proteins provide channels, pumps, and transporters that allow for the selective passage of specific substances across the membrane.
• Foundation for Structure: The bilayer serves as the basic structural framework into which proteins are inserted or associated, enabling the diverse functions of different cell membranes (e.g., plasma membrane, organelle membranes).

Gorter and Grendel's work, despite some inaccuracies in their experimental details (like underestimating the lipid content or not considering all lipid types), was remarkably insightful and correctly deduced the bilayer nature, laying the groundwork for all subsequent membrane models.