Difference Between Active and Passive Diffusion

The key difference between active and passive diffusion is that the active diffusion or active transport uses energy to transport molecules against the concentration gradient while the passive diffusion does not need energy since it occurs along the concentration gradient.

There are different types of transport systems that help moving substances from one place to another. Basically, there are two mechanisms of transportation; they are the active and passive transport or diffusion. The main criterion for the difference between active and passive diffusion is energy consumption. Active transport consumes energy while passive transport does not require energy to occur. Furthermore, there are some more differences between active and passive diffusion. The main purpose of this article is to discuss those differences while giving an understanding of the two mechanisms.

CONTENTS

1. Overview and Key Difference
2. What is Active Diffusion
3. What is Passive Diffusion
4. Similarities Between Active and Passive Diffusion
5. Side by Side Comparison – Active vs Passive Diffusion in Tabular Form
6. Summary

What is Active Diffusion?

Active transport (active diffusion) is a type of diffusion that consumes energy to transport molecules across a membrane from a lower concentration to higher concentration against the concentration gradient. It differs from passive diffusion since it occurs against the concentration gradient and the need for energy. The net movement of molecules occurs from low concentration region to high concentration region. Active diffusion is responsible for the accumulation of essential nutrients such as ions, glucose, amino acids, etc., inside the cells.

Furthermore, active transport can be either primary active transport or secondary active transport. Primary active transport utilizes the energy of ATP while the secondary active transport utilizes the electrochemical gradient. Accordingly, active transport occurs in humans, animals and plant cells. Transportation of mineral ions from soil solution to the root hair cells and intestinal uptake of sugars occur due to this active diffusion mechanism.

What is Passive Diffusion?

Diffusion is one of the commonest methods found in passive transport. It is the process that facilitates the movement of molecules from a higher concentration region to a lower concentration region along the concentration gradient. Therefore, passive diffusion is a movement of molecules from a higher concentration region to a lower concentration region across a membrane along the concentration gradient. In here,  the net movement of molecules occurs from a high concentration to a low concentration due to the kinetic energy. Hence, it does not require cellular energy.

Passive diffusion has several types such as simple diffusion, facilitated diffusion, osmosis, etc., based on the method of transportation. In simple diffusion, solutes travel from high concentration to low concentration down a concentration gradient without the involvement of a membrane. In facilitated diffusion, special membrane proteins called carrier or channel proteins involve in the processes. Since the carrier or channel proteins facilitate the process, it got the name ‘facilitated diffusion’.

Some large molecules cannot simply pass through the membranes. Therefore, they need special support for transportation. That is; the transport proteins embedded in the cell membrane are modified to do this activity. In here, for the purpose of movement, the specific molecule binds with career protein. However, it is still happens through a concentration gradient.

Finally, osmosis is a different type of diffusion where the water molecules move across the semi-permeable or selectively permeable membrane from the high water potential to low water potential. Similarly, filtration is also a type of passive transport system but not considered as a diffusion.

What are the Similarities Between Active and Passive Diffusion?

• Active and Passive Diffusion are two types of processes that involve the movement of molecules from one place to another place.
• Both processes occur in cells.
• Also, both are extremely important processes for living organisms.

What is the Difference Between Active and Passive Diffusion?

Active diffusion utilizes energy while passive diffusion does not. Thus, it is the key difference between active and passive diffusion. Furthermore, a significant difference between active and passive diffusion is that the active diffusion happens from low concentration to high concentration against the concentration gradient while the passive diffusion happens from high concentration to low concentration along the concentration gradient.

Moreover, the net movement of molecules also contributes to a difference between active and passive diffusion. Net movement of molecules is from low concentration to high concentration in active transport while it is from high concentration to low concentration in passive diffusion.

Besides, there are two main types of active transport; primary and secondary active transport while there are four types of passive diffusion; simple diffusion, facilitated diffusion, osmosis and filtration.

The below infographic on the difference between active and passive diffusion presents these differences as a side by side comparison.

Summary – Active vs Passive Diffusion

Active and passive diffusion are two methods that facilitate the movements of molecules. In summarizing the difference between active and passive diffusion, the key difference between active and passive diffusion is the energy requirement. Active transport requires energy. But, passive diffusion does not require energy.

Furthermore, active transport occurs against the concentration gradient while passive diffusion occurs along the concentration gradient. Moreover, the net movement of molecules in active transport takes place from low concentration to high concentration while the net movement of molecules in passive diffusion takes place from high concentration to low concentration.

Reference:

1. “Active Transport.” Wikipedia, Wikimedia Foundation, 30 Dec. 2018. Available here 
2. “Passive Transport.” Wikipedia, Wikimedia Foundation, 19 Dec. 2018. Available here  

Image Courtesy:

1.”Scheme sodium-potassium pump-en”By LadyofHats Mariana Ruiz Villarreal – Own work. (Public Domain) via Commons Wikimedia  
2.”Blausen 0213 CellularDiffusion.”By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work, (CC BY 3.0) via Commons Wikimedia