Why are keratinized skin cell so hard to penetrate?

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Why are keratinized skin cell so hard to penetrate?

Postby jewish_scientist » Wed Apr 05, 2017 1:41 pm UTC

As a skin cell ages, it moves closer and closer to the surface. At the same time, it undergoes a process called keratinization, which is defined as the process by which keratin builds up in a cell. By the type the cell is at the outer most layer, it is almost pure keratin. This cell, along with other keratinazed cells, for a matrix (the physical equivalent of a geometric tessellation). After a little while, the cell falls off and is replaced by the cell one layer lower than it. Almost all microorganisms cannot penetrate this matrix, which is by holes in this matrix (orifices and cuts) are the most likely places for an infection to occur.

I am 99.99999999999999999999999999999999999999999999999999998% sure that everything I just wrote is correct. What I cannot understand is why this matrix is so resistant to microorganisms. Keratin is the protein that makes up many tough structures e.g. a rhino's horn, but those structures are not so fragile that the outer layers come off. Viruses can penetrate the cellular membrane, so why are they stopped by a protein matrix?

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Re: Why are keratinized skin cell so hard to penetrate?

Postby p1t1o » Wed Apr 05, 2017 2:05 pm UTC

I believe it is a physical effect. It is an effective barrier because the filaments are tough and tightly bundled together. A "protein" does not have to be a wet, digestible, nutrient-rich mass. "Protein" just means "made of amino acids" and in some combinations, they can form strong fibres and networks. In keratin, there is a large proportion of amino acids that like to bond together via "sulphur bridges", these are fully covalent chemical bonds that are some of the strongest bonds found in proteins.

Compared to a cell membrane, it is like tank armour. A cell membrane is essentially liquid in phase consisting of fatty molecules only loosely bonded together by much weaker mechanisms like Van der Waals forces.

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