Particles move across the cell membrane through several processes. They move by osmosis, diffusion, active transport, or by facilitated transport. Osmosis is the movement of particles from a region of low concentration to a region of high concentration through a semi-permeable membrane (Helmenstine, 2020). Diffusion is the movement of particles from a region of high concentration to a region of low concentration with the aim of balancing the concentration throughout the medium (Helmenstine, 2020). A good example of where osmosis occurs is where plant roots take up water from the soil. A good illustration of diffusion is when a highly concentrated drop of food coloring is dropped into a glass of water, and soon the food coloring colors the whole glass of water. Both osmosis and diffusion are very different processes, but they also share some similarities. One major similarity between the two processes is that they are both passive processes, in the sense that they do not require any energy to be applied for them to take place (Helmenstine, 2020).
Osmosis and diffusion are also similar in the sense that they both serve to balance out the concentration of the solutions in which they take place. However, the differences between the two processes outweigh their similarities. One major difference between the two processes is that in diffusion, any substance can move from a region of high concentration to a region of low concentration, while in osmosis, only water or any other solvent can move from a region of high concentration to a region of low concentration (Helmenstine, 2020). Also, diffusion occurs in a wide range of mediums such as solids, liquids, and gases, while osmosis can only take place in one medium: liquids. Another difference between the two processes is that in diffusion, the concentration of the substance in high concentration is transported to balance out the concentration of the region of low concentration, while in osmosis, there is an unequal concentration of the solvent after the particles have moved through the semi-permeable membrane (Helmenstine, 2020).
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Active transport is the movement of molecules from one region to another against the concentration gradient. A good example of where active transport occurs is in the human body, where amino acids are transported into the intestinal lining cells (Anderson, 2017). Facilitated transport, on the other hand, is the movement of molecules from one region to another down the concentration gradient. A good example of where facilitated transport occurs is in the human body, where this process plays a preeminent role in how the body retains water (Anderson, 2017). Through facilitated transport, water is transported from the kidney tubules and into the capillaries, a process that ensures that excessive amounts of water are not excreted along with urine.
Both active and facilitated transport are different processes and, as such, have similarities and differences. The first similarity between the two processes is that they transport ions, sugars, and salts across a membrane (Anderson, 2017). The second similarity between the two processes is that they both use proteins as a medium of transporting molecules in and out of the cells. Active transport and facilitated transport are also different in a number of ways. The first difference between the two processes is that facilitated transport moves molecules down their concentration gradient, from a region of high concentration to a region of low concentration. Active transport, on the other hand, moves molecules against their concentration gradient, from a region of low concentration to a region of high concentration (Anderson, 2017). Another difference between the two processes is that active transport requires energy to take place, whereas facilitated transport does not require any energy. Besides, active transport involves the transportation of rather large substances, while facilitated transport involves the transportation of small substances (Anderson, 2017). Last but not least, active transport moves substances in only one direction while facilitated transport moves substances in different directions.
References
Anderson, H. (2017). Passive diffusion vs active transport - examples, and differences . https://www.microscopemaster.com/passive-diffusion-vs-active-transport.html .
Helmenstine, Anne Marie, Ph.D. (2020). Differences between Osmosis and Diffusion. Retrieved from https://www.thoughtco.com/difference-between-osmosis-and-diffusion-609191
