3. Introduction
◦ Transportation is the process of movement or distribution of different materials or goods from
one place to another.
◦ In general, we humans make use of different means of transportation.
◦ Similarly, the living system, including plants, animals, and humans has an amazing network of
transportation systems, involved in circulating food, minerals, hormones, oxygen, carbon
dioxide, waste products, etc.
4. Definition
◦ Passive transport is the fundamental movement of ions and other molecular substances within
the cells along the concentration gradient, without any external energy.
◦ It is also known as passive diffusion.
5. Types of passive transport
◦ Simple diffusion
◦ Facilitated diffusion
◦ Filtration
◦ Osmosis
6. Simple diffusion
◦ Diffusion is the movement of substances from a region of higher concentration to a lower
concentration.
◦ It is an important process in living things required for different life processes.
◦ The substances move in and out of the cells by simple diffusion.
7. Facilitated diffusion
◦ Facilitated diffusion is the passive transportation of ions or molecules across the cell membrane
through specific transmembrane integral proteins.
◦ The molecules, which are large and insoluble require a carrier substance for their transportation
through the plasma membrane.
◦ This process does not require any cellular or external energy.
8. Filtration
◦ Filtration is the process of separating solids from liquids and gases.
◦ The selective absorption of nutrients in the body is an example of filtration.
◦ This process does not require any energy and takes place along the concentration gradient.
◦ The kidneys are an example of a biological filter.
◦ The blood is filtered by the glomerulus and the necessary molecules are reabsorbed.
9. Osmosis
◦ In the process of osmosis, water and other molecules pass through a selectively permeable
membrane in order to balance the concentration of other substances.
◦ Osmosis is affected by the concentration gradient and temperature.
◦ The greater the concentration gradient, the faster the rate of osmosis.
◦ Also, the rate of osmosis increases with the increase in temperature.
10. Examples of passive transport
◦ Ethanol enters our bodies and hits the bloodstream. This happens because the ethanol
molecules undergo simple diffusion and pass through the cell membrane without any external
energy.
◦ Reabsorption of nutrients by the intestines by separating them from the solid waste and
transporting the nutrients through the intestinal membrane into the bloodstream.
◦ When a raisin is soaked in water the water moves inside the raisin by the process of osmosis and
it swells.
11. Conclusion
◦ Passive transport is a physiological mechanism of transporting molecules across the membrane
that favors the concentration gradient.
◦ Without any expenditure of energy, the process transfers essential molecules, nutrients, and
gases to the organism’s body required for their living.
