In the year 1925, who extracted lipids from an erythrocyte sample and found that lipid monolayers are good for measuring molecular surface area versus lateral pressure?

Correct — B. In 1925 Evert Gorter and Francois Grendel extracted the lipids from red blood cells, spread them as a monolayer on a water surface, and measured the area that film covered against the lateral pressure applied to it.

The area came out at roughly twice the total surface area of the cells the lipids had come from.

From that ratio they concluded the membrane is two molecules thick — the first statement of the lipid bilayer, and the work option (b) names.

Why the others are wrong

• (a)
  Avery and Buck — Not a pairing on membranes. Oswald Avery is remembered for the 1944 work identifying DNA as the transforming principle, which is genetics rather than membrane structure.
• (c)
  Carson and Eccles — Neither name belongs to the 1925 monolayer work. John Eccles shared the 1963 Nobel Prize for the ionic mechanisms of the nerve cell membrane, four decades later.
• (d)
  Margulis and Ruska — Lynn Margulis is associated with the endosymbiotic origin of mitochondria and chloroplasts, and Ernst Ruska with building the first electron microscope. Neither measured erythrocyte lipids.

Membrane models arrived in a sequence you can hold in order.

Gorter and Grendel (1925) gave the bilayer. Davson and Danielli (1935) wrapped that bilayer in protein layers on both faces. Singer and Nicolson (1972) replaced the protein sandwich with the fluid mosaic model, in which proteins float in and pass through a fluid lipid bilayer.

The fluid mosaic model is the one still taught, and the 1925 measurement is the observation the whole sequence is built on.

Key facts

• Gorter and Grendel, in 1925, measured erythrocyte lipids as a monolayer and found an area about twice the cell surface, implying a bilayer.
• The Davson-Danielli model of 1935 placed protein layers on both surfaces of the lipid bilayer.
• Singer and Nicolson proposed the fluid mosaic model in 1972.

Common traps

• Attaching the bilayer discovery to Singer and Nicolson, who explained how proteins sit in the membrane, not that it is two layers thick.
• Recognising one famous surname in a wrong option and choosing on that alone.

No directly related past PYQ was found.