3 Passive Transport Examples: Explanation You Should Know


Passive transport doesn’t consume cell energy during transportation of molecules.

Passive transport facilitates the transportation of molecules with put consuming cell energy.

The transportation of molecules or ions occurs from greater concentration to lesser concentration gradient in Passive transport.

Simple diffusion:

In this process the molecules travel from high concentration gradient to low concentration gradient until the concentration of molecules becomes neutral.

The simple diffusion occurs in gases and liquids as in these cases the molecules move freely.

This process doesn’t require any energy.

It aids the transfer of molecules in to and out of the cell. This is very important cell activity for during life cycles.

Facilitated diffusion:

Facilitated transport supports the movement of molecules or ions without consuming cell energy with respect to their concentration gradient. Hence this can be the passive transport process.

In this process only a few molecules are allowed to travel through the membrane as it is a selective process. Basing on the electric charge and pH levels the molecules are diffused through the membrane.

The membrane doesn’t allow the passage of the hydrophilic, polar and charged ions. The facilitated diffusion enhances the passage of molecules like glucose, amino acids, nucleic acids, and ions like sodium, potassium, and calcium.

The facilitated diffusion works according to the Brownian movement.

Image Credit: Facilitated Diffusion Wikipedia

The facilitated diffusion is affected by four factors.

  • Temperature
  • Concentration
  • Diffusion distance
  • Size of the molecules

Temperature:

If there is rise in the temperature there is a rise in the diffusion rate of molecules because of increase in energy. Thus the facilitated diffusion is directly proportional to the temperature.

Concentration:

The molecules of ions are transported from greater concentration to lesser concentration.

Diffusion distance:

If there a small distance the diffusion rate will be high. Thus the facilitated diffusion is inversely proportional to the diffusion distance.

Size of the molecules:

If the molecule is small in size there will be high diffusion rate and vice versa. Hence the facilitated diffusion is inversely proportional to the size of molecules.

The facilitated diffusion is performed by the protein channels which are bounded in membrane. Namely they are channel proteins and carrier proteins.

Channel proteins:

These proteins aid the in and out of the molecules. These are two types.

Gated channel proteins:

They control the entry and exit of the molecules in a cell. They act as a gate.

Open channel proteins:

They make a pore in the cell membrane and enchances the flow of molecules.

Carrier proteins:

These are membrane bound and carry the substances into and out of the cell.

Glucose transporters:

These transporters play a pivotal role in the glucose transport in a cell. They are two types. Namely they are sodium glucose transporters and facilitative glucose transporters.

Aqua porins:

They facilitate the passage of water molecules through lipid bilayer.

Ion channels:

These channels enhance the passage of ions like sodium and potassium through the plasma membrane.

Filtration:

Filtration is the method of separation of solid matter which are suspended in liquids with the help of filters.

The filter does not allow the passage of solid matter but allows the liquids to travel. The solid substance is known as residue and the liquid matter is known as filtrate. Different types of materials can be used as a filter. For example paper, sand, cloth.

Types of filtration:

  • Vacuum filtration
  • Centrifugal filtration
  • Gravity filtration
  • Multilayer filtration

Vacuum filtration:

In this type of filtration the two funnels are used along with the filter paper which are different in size but same kind. The vacuum pump draws the fluid through the filter.

Centrifugal filtration:

In this filtration the substances are rotated at very high speed in horizontal manner. By this process the heavy substances are separated from light weight substances.

Gravity filtration:

In this filtration the filter paper is placed in the glass funnel. The insoluble particles remain on the paper and the liquid travels down.

This process works on gravity.

passive transport examples
Image Credit: Gravity Filitration Wikipedia

Multilayer filtration:

In this different layers of filters are used with different materials like sand, charcoal as they contain different size pores.

If the mixture is poured the particles are separated at different layers depending on the particle size.

For example sewage water is purified in this process, drinking water purification.

Uses of filtration:

Kidneys are best examples for biological filters as the blood gets filtered in glomerulus. In this process the important nutrients and molecules are reabsorbed.

This is most likely used in pharmaceutical industry to separate the impurities as well as sediments.

Sewage water is purified through filtration process.

Drinking water can also be purified by this process.

Osmosis:

Osmosis is nothing but the diffusion of molecules through a semipermeable membrane.

During osmosis the molecules are diffused from greater concentration solution to lesser concentration solution.

This is a passive transport as it does not consume energy.

Thus process lead the equalization of solutions by maintaining the solute concentration.

Osmosis is a pivotal process in our biological systems.

The ions, games, molecules, proteins, and polysaccharides are being transferred through osmosis process.

In osmosis process the water molecules are transported through aqua porins.

passive transport examples
Image Credit: Osmosis Wikipedia

Types of Osmosis:

  • Endosmosis
  • Exosmosis

Endosmosis:

Whenever the cell is placed in hypotonic solution the more molecules enter the Cell and this leads to the turgidity of cell. This process can be called as endosmosis.

Exosmosis:

Whenever the cell is placed in hypertonic solution the solvent molecules come out of the cell. This leads flaccidity of the cell. Thus this process is known as exosmosis.

Examples of osmosis:

The absorption of water from soil done by osmosis process.

During absorption of water the water flows into roots as they have higher concentration of water.

The guard cells in plant leaves can also be affected through osmosis.

If the plants have plenty of water then the guard cells become swollen and opens the stomata.

This helps in gaseous exchange in plants.

Human body can also absorb water if it is placed in water for longer time.

Importance of osmosis:

It regulates the turbidity of the cells.

 It can also regulate the balance between water and internal fluids.

It enhances the absorption of nutrients and release of waste substances.

It controls the water flow in plants.

Conclusion:

Thus the passive transport of molecules , ions, and substances occurs with respect to their concentration instead of consuming cell energy.

Narne Naga Srilakshmi

Hi...I am Nagasrilakshmi Narne, a postgraduate in Biotechnology and English. also completed my B.Ed. I worked in Vimtalabs as a project trainee and I have work experience as a faculty of English. So I can explain topics in simple language. Let's connect through LinkedIn:https://www.linkedin.com/in/narne-naga-srilakshmi-55069334

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