Movement and accumulation of ions across a membrane against their concentration gradient can be explained by

In mass flow,various substances move independently according to their

Read the following statements regarding porins and select the correct option given below:
$I$. Porins are transport proteins.
$II$. Channel proteins are a type of transport protein,which are usually gated.
$III$. Carrier protein binds the particular solute to be transported.
$IV$. Particular solute is delivered to the other side of the membrane by carrier proteins.

Why does the rate of diffusion of a substance along the concentration gradient not increase continuously,even when the concentration difference of the molecules across the membrane increases?

When a carrier protein facilitates the movement of two molecules across the membrane in the same direction,it is called:

In which of the following pathways does the flow of water occur from cell to cell through their protoplasm?