Question

Which of the following pieces of evidence does not contradict the Davson - Danielli model of membrane structure?

• A. Lipids are arranged in a bilayer with the hydrophobic group in contact with each other.
• B. Treatment of membranes with salts, it removes lipids.
• C. Freeze-fracture of membranes results in particle studded membrane face; particles are rarely present and are highly pure lipid membranes.
• D. Proteins from $\alpha$-helical structures with the hydrophobic group that interacts with the fatty acid chain of lipids.

Answer 1

The correct option is A Lipids are arranged in a bilayer with the hydrophobic group in contact with each other.

According to the Lamellar or Sandwich models, cell membranes contain both protein and lipids in distinct layers. Two such models were popular Danielli and Davson model and Robertson's model. Robertson gave unit membrane concept which proposed that all biomembranes have a trilaminar structure. According to Danielli and Davidson, 1935, plasmalemma is a double phospholipid layer surrounded on either side by a layer of hydrated globular proteins in the form of "Protein-Lipid-Lipid-Protein". The hydrophobic or non-polar tails of the two lipid layers are towards the centre. Thus, the correct answer is option A.