Who proposed the concept of the unit membrane?

The main structural component of the plasma membrane of various cellular organelles is:

Given below are two statements.
Statement-$I$: Cell wall is freely permeable.
Statement-$II$: Plasma membrane is selectively permeable.
Choose the correct answer from the options given below with reference to the structure of root hair.

At which surface does the Donnan equilibrium occur?

$A$ boy is studying the transport of a certain type of molecule into a cell. He finds that the transport slows down when the cells are poisoned with a chemical that inhibits energy production. Under normal circumstances,the molecules studied by the boy are probably transported by

During the transport of sugar or amino acids through the cell membrane,what is the movement of $Na^+$ ions?