Simple Diffusion: Process, Examples and Difference with Osmosis and with Facilitated Diffusion

The simple broadcast is the physical process by which substances move from a region where they are highly concentrated to areas where the concentration of that substance is lower. Simple diffusion is a spontaneous process that does not require energy, but is promoted by a concentration gradient.

The substances that are dissolved are called solutes, they move through a solution (or a gas) by random movements. Random movement is defined as the movement that happens by chance, where there is no regular order or system by which the movements of the particles change in a solution or gas.

Simple diffusion Simple diffusion

If the molecules are small enough, this simple diffusion can occur through the cell membranes, between the individual phospholipids that make it up. The membranes can be permeable, waterproof or semipermeable.

A permeable membrane is one that lets through any substance, a waterproof membrane does not pass any substance and a semipermeable membrane only allows the passage of certain substances.

Index

  • 1 Simple diffusion process
  • 2 Simple broadcast examples
    • 2.1 Gas exchange in the respiratory system
    • 2.2 Dissemination of tea in hot water
  • 3 Differences between simple diffusion and facilitated diffusion
  • 4 Differences between simple diffusion and osmosis
  • 5 References

Simple diffusion process

The simple diffusion is carried out through actions of the hydrogen bonds that are formed between the water molecules and the solutes dissolved in it. The water molecules move randomly and eventually surround the individual solute molecules, which maximizes the opportunity to form the hydrogen bonds.

Thus, if a mixture of a substance were made in water, initially the substance would be concentrated in one place, the initial one. At that time the concentration gradient is very high.

As time passes the molecules move and collide with each other; This movement promotes the formation of bonds between the particles of solute and the solvent. However, these links break quickly because they are very weak and this is the property that allows them to be distributed throughout the space until reaching equilibrium.

At that point, where the solute is evenly distributed throughout the solution, the strength of the concentration gradient is over.

Simple broadcast examples

Gas exchange in the respiratory system

In the respiratory system of the lung animals, oxygen (O2) and carbon dioxide (CO2) are constantly exchanged. Animals absorb oxygen and expel carbon dioxide by simple diffusion.

In the lungs the concentration of oxygen is higher than in the blood, so there is a concentration gradient between these two regions, and this causes the diffusion of oxygen from the lungs to the blood to be promoted.

Similarly, having more carbon dioxide molecules in the blood than in the lungs, these will tend to move from the blood to the lungs.

Dissemination of tea in hot water

When you prepare a cup of tea initially there is only hot water without any solute. By placing the tea bag in the hot water it begins to release the tea particles from the bag - where there is a higher concentration of tea - into the water, where the tea concentration is lower.

The movement of the molecules is favored by the initial concentration gradient of the tea. Eventually, the diffusion of the tea causes the concentrations to equalize throughout the cup and the solution to become homogeneous (all of the same color is seen). At this point there is no concentration gradient.

Differences between simple diffusion and facilitated diffusion

- In simple diffusion the particles cross the cell membrane freely, without the"help"of other structures. In contrast, in facilitated diffusion the molecules are transported through small protein channels that cross the entire membrane.

- Simple diffusion is slower than facilitated diffusion.

- The simple diffusion is not specific to the solute, only that the particles to be transported must be hydrophobic so that they can cross the cell membrane without problem. In contrast, in the facilitated diffusion, specific solutes are transported.

- Simple diffusion can not be inhibited, while facilitated diffusion can be inhibited by specific molecules that bind to the transport channels.

- Simple diffusion is always a passive process, that is, it does not require the energy coming from the ATP. In contrast, facilitated diffusion can be an active or passive mechanism, depending on whether or not it requires the energy of the ATP.

- In simple diffusion the substances always move in favor of their concentration gradient. Conversely, in the facilitated diffusion the substances pass the membrane against or in favor of their concentration gradient.

- Simple diffusion allows the passage of small and non-polar molecules (hydrophobic), while facilitated diffusion allows the passage of large and polar (hydrophilic) molecules.

Differences between simple diffusion and osmosis

- Simple diffusion refers to the movement of any substance according to its concentration gradient; On the other hand, osmosis refers exclusively to the movement of water according to its water potential.

- Simple diffusion occurs in solid liquids and gases. On the contrary, osmosis can only occur in liquid medium.

- Simple diffusion does not require a semipermeable membrane, while osmosis is a process that occurs through a semipermeable membrane.

- Simple diffusion helps to equalize the concentrations of solutes dissolved in the available space. Osmosis does not favor the equal concentration of water on both sides of the semipermeable membrane.

- Simple diffusion can occur between different types of solvents. In contrast, osmosis can only occur between similar solvents and in biological systems. This solvent is usually water.

- In simple diffusion the particles are distributed in all directions, in osmosis the flow of molecules is basically in the same direction.

- The simple diffusion process can not be stopped or reversed. In contrast, osmosis can be stopped or reversed if additional pressure is applied on the side of the membrane where there is less water available.

References

  1. Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K. & Walter, P. (2014). Molecular Biology of the Cell (6th ed.). Garland Science.
  2. Campbell, N. & Reece, J. (2005). Biology (2nd ed.) Pearson Education.
  3. Lodish, H., Berk, A., Kaiser, C., Krieger, M., Bretscher, A., Ploegh, H., Amon, A. & Martin, K. (2016). Molecular Cell Biology (8th ed.). W. H. Freeman and Company.
  4. Purves, W., Sadava, D., Orians, G. & Heller, H. (2004). Life: the science of biology (7th ed.). Sinauer Associates and W. H. Freeman.
  5. Solomon, E., Berg, L. & Martin, D. (2004). Biology (7th ed.) Cengage Learning.
  6. Thibodeau, P. (2013). Anatomy and Physiology (8 th ). Mosby, Inc.
  7. Tortora, G. & Derrickson, B. (2012). Principles of Anatomy and Physiology (13th ed.). John Wiley & Sons Inc.


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