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Passive Transport is a type of cellular movement that involves movements of ions and molecules across the cellular membrane. It does not require energy to move from a higher concentration to a lower concentration.
- The reason for no use of energy is that the movement is done downhill.
- Passive Transport is based on the second law of thermodynamics.
- The process increases the overall entropy of the system.
- The elements tend to follow Fick's First Law.
- Passive transport is the opposite of Active Transport.
- Active Transport involves the movement of ions from low concentration to high concentration.
- It requires energy for the movement of ions and molecules.
- All living systems use this method of transporting various things such as food, oxygen, hormones, etc.
Read More: Discovery of Cells
| Table of Content |
Key Terms: Passive Transport, Active Transport, Second Law of Thermodynamics, Diffusion, Osmosis, Facilated Diffusion, Filtration
What is Passive Transport?
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Passive Transport is a transportation method that requires the movement of molecules or ions from a higher concentration to a lower concentration. It does not require energy to move the molecules across the cell membrane.
- The rate at which the movement of ions will occur depends on the permeability of the cell membrane.
- Passive transport is classified into four types, namely Diffusion, Facilitated Diffusion, Filtration, and Osmosis.
- The movement of ions takes place along a concentration gradient.
- Passive transport depends upon the movement of lipids and proteins.
Passive Transport
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Types of Passive Transport
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Passive Transport is divided into four categories which are as follows:
Diffusion
Diffusion is defined as the movement of molecules from a region of higher concentration to a lower concentration. The concentration difference between the two areas is known as the concentration gradient, and the concentration gradient continues until the gradient has been neutralized.
- Substances diffuse according to their concentration gradient.
- After the completion of the diffusion process, the molecules will roam in the space.
- There will be no net movement of molecules from one concentration to another concentration.
- Several factors affect the rate of diffusion, which are the mass of the solute, the temperature of the environment, and the distance travelled.
- Example of Diffusion: the exchange of gas that occurs during the respiration process in the human body.
Facilitated Diffusion
Facilitated Diffusion, also known as carrier-mediated osmosis, is a transportation process during which molecules are transported with the help of proteins in the plasma membrane. Integral membrane proteins are used in facilitated Diffusion to transport the molecules across the hydrophobic regions in the membrane.
- Channel proteins help in the facilitated Diffusion by forming a hydrophilic passage.
- The passage is formed with the plasma membrane with the help of polar and charged substances.
- Examples of Facilitated Diffusion: Ion channels, Glucose transporters, and aquaporins.
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Filtration
Filtration is the process of separating one molecule from the other, which is called filtration. It is also the movement of solute and water molecules within a cell membrane due to hydrostatic pressure generated by the cardiovascular system of the body.
- The filtration process doesn’t require any energy.
- In this, the size of the solute will be allowed to pass through the membrane.
- It depends on the size of the membrane pores.
- Example of Filtration: Water and Inorganic Ions are regulated by the Kidney.
Read More: Why is respiration an exothermic reaction?
Osmosis
Osmosis is defined as the movement of water and other molecules from an area of low solute concentration to an area of higher solute concentration. It occurs according to the water’s concentration gradient and follows until the concentration gradient neutralizes.
- Osmosis is affected by temperature and Concentration gradient.
- It is inversely proportional to the concentration of solutes.
- The greater the concentration gradient, the faster will be the rate of osmosis.
- Examples of Osmosis: Kidney dialysis
Types of Passive Transport
Read More: Difference between Lipids and Fats
Things to Remember
- Passive Transport is a natural phenomenon that does not require any external energy.
- It involves the movement of ions from higher to lower concentrations.
- Passive Transport is categorized as Diffusion, Facilitated Diffusion, Filtration, and Osmosis.
- Diffusion is the movement of molecules from the region of higher concentration to lower concentration.
- Facilitated Diffusion is a transportation process during which molecules are transported with the help of proteins in the plasma membrane.
- Filtration is the process of separating one molecule from the rest of the molecules.
- Osmosis is the movement of water and other molecules from an area of low solute concentration to an area of higher solute concentration..
Read More: Difference Between Catabolism and Anabolism
Sample Questions
Ques. Name all the substances which are absorbed by active, passive, and simple diffusion in the digestion process? (2 marks)
Ans. The substances absorbed by simple diffusion include glycerol, monoglycerides and fatty acids (fat digestion), water-soluble vitamins, and water. The substances absorbed by active diffusion include Sodium ions. Passive Diffusion involves Vitamin C and Vitamin B.
Ques. Why is Diffusion also termed passive transport? (2 marks)
Ans. There is no energy involved during the passive transport, and the movement of molecules from a region of higher concentration to a lower concentration is called diffusion. The concentration difference between the two areas is known as the concentration gradient, and the concentration gradient continues until the gradient has been neutralized.
Ques. What allows the movement of a substance from a higher to a lower gradient? (2 marks)
Ans. Changes in the concentration gradient allow the substances to move from a higher to a lower gradient. It is based on the second law of thermodynamics. The overall process increases the overall entropy of the system. In this, the elements tend to follow Fick's First Law.
Ques. Are Diffusion and Passive Transport the same? (2 marks)
Ans. Passive transport is the movement of molecules from a high gradient to a lower gradient, and it does not require energy to move those molecules. This transfer of molecules is also termed Diffusion, and hence, diffusion is the part of Passive Transportation.
Ques. Differentiate between Active and Passive Transport? (4 marks)
Ans. The differences between Active and Passive Transport are as follows:
| Active Transport | Passive Transport |
|---|---|
| Active Transportation is the movement of molecules from a lower concentration gradient to a region of the higher concentration gradient. | Passive Transportation is the movement of molecules from a higher concentration gradient to a region of the lower concentration gradient. |
| It requires energy for movement of molecules. | It does not requires energy for movement of molecules. |
| It is an energetic and quick process. | It is an extremely slow process. |
| Active Transport occurs in one direction. | Passive Transport occurs in both direction. |
Ques. What importance do active and passive transport hold? (2 marks)
Ans. Active Transport involves the movement of molecules from a lower concentration region to a higher concentration gradient. Similarly, Passive Transport involves the movement of molecules from a higher concentration region to a lower concentration gradient. Regulation of entry and exit of ions and molecules within a cell is done by active and passive transportation. These two processes allow only specific molecules to pass through the membrane, disallowing the others.
Ques. What are the different types of Passive Transport? (4 marks)
Ans. Passive Transport is categorized as Diffusion, Facilitated Diffusion, Filtration, and Osmosis.
- Diffusion is the movement of molecules from the region of higher concentration to lower concentration.
- Facilitated Diffusion is a transportation process during which molecules are transported with the help of proteins in the plasma membrane.
- Filtration is the process of separating one molecule from the rest of the molecules.
- Osmosis is the movement of water and other molecules from an area of low solute concentration to an area of higher solute concentration.
Ques. What are the examples of Diffusion, Facilitated Diffusion, Filtration, and Osmosis? (4 marks)
Ans. The examples of Diffusion, Facilitated Diffusion, Filtration, and Osmosis are as follows:
- Example of Diffusion: the exchange of gas that occurs during the respiration process in the human body.
- Examples of Facilitated Diffusion: Ion channels, Glucose transporters, and aquaporins
- Example of Filtration: water and inorganic ions are regulated by the Kidney.
- Examples of Osmosis: Kidney dialysis.
Ques. Explain the process of transportation? (4 marks)
Ans. Transportation involves the movement or distribution of goods and materials from one place to another is called Transportation. Similarly, all living systems have this method of transporting various things such as food, oxygen, hormones, etc. The human body follows two types of Transportation- Active transportation and Passive Transportation.
- Active Transportation- The movement of ions and molecules from low concentration to High concentration within a cell membrane with the help of energy is called Active Transportation.
- Passive Transportation- The movement of molecules from a high concentration to a low concentration across the cell membrane, without the use of energy, is called Passive concentration.
Ques. Explain the term osmosis? (2 marks)
Ans. Osmosis is defined as the movement of water and other molecules from an area of low solute concentration to an area of higher solute concentration. It occurs according to the water’s concentration gradient and follows until the concentration gradient neutralizes. The process is affected by temperature and concentration gradient. It is inversely proportional to the concentration of solutes which means greater the concentration gradient, the faster will be the rate of osmosis. Example of Osmosis includes Kidney dialysis
Ques. What is the difference between diffusion and facilitated diffusion? (4 marks)
Ans. The difference between diffusion and facilitated diffusion are as follows:
| Diffusion | Facilitated Diffusion |
|---|---|
| Diffusion involves movement of ions when electrochemical barrier is applied on the two side of membrane. | Facilitated Diffusion is a type of diffusion which involves interaction of solutes and its particles. |
| It is a type of passive transport. | It is a type of passive and biological transport. |
| The process of diffusion is slow. | The process of diffusion is fast. |
| It take place in the direction of concentration gradient. | It take place in the direction of concentration gradient and also against the direction of gradient. |
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