Question

What is passive transport?

Answer 1

Passive transport is a movement of ions and other atomic or molecular substances across cell membranes without need of energy input.

Explanation:

It is driven by the tendency of the system to grow in entropy.

Sometimes cell membranes act as channels to help the movement along. There may also be in between transport process where very small molecules are able to cross a semipermeable membrane.

The rate of passive diffusion depends upon the permeability of the cell membrane. It depends on the organisation and characteristics of the membrane lipids and protein.

The four main kinds of passive transport are -

Simple diffusion
Facilitated diffusion
Filteration
Osmosis