Osmolytes are low-molecular-weight organic compounds that influence the properties of biological fluids. Osmolytes are a class of organic molecules that play a significant role in regulating osmotic pressure and maintaining cellular homeostasis in various organisms, particularly in response to environmental stressors.[1] Their primary role is to maintain the integrity of cells by affecting the viscosity, melting point, and ionic strength of the aqueous solution. When a cell swells due to external osmotic pressure, membrane channels open and allow efflux of osmolytes carrying water, restoring normal cell volume.

These molecules are involved in counteracting the effects of osmotic stress, which occurs when there are fluctuations in the concentration of solutes (such as ions and sugars) inside and outside cells. Osmolytes help cells adapt to changing osmotic conditions, thereby ensuring their survival and functionality.[2] Osmolytes also interact with the constituents of the cell, e.g., they influence protein folding.[3][4] Common osmolytes include amino acids, sugars and polyols, methylamines, methylsulfonium compounds, and urea.

Case studies

Natural osmolytes that can act as osmoprotectants include trimethylamine N-oxide (TMAO), dimethylsulfoniopropionate, sarcosine, betaine, glycerophosphorylcholine, myo-inositol, taurine, glycine, and others.[5][6] Bacteria accumulate osmolytes for protection against a high osmotic environment.[7] The osmolytes are neutral non-electrolytes, except in bacteria that can tolerate salts.[6] In humans, osmolytes are of particular importance in the renal medulla.[8]

Osmolytes are present in the cells of fish, and function to protect the cells from water pressure. As the osmolyte concentration in fish cells scales linearly with pressure and therefore depth, osmolytes have been used to calculate the maximum depth where a fish can survive. Fish cells reach a maximum concentration of osmolytes at depths of approximately 26,900 feet (8,200 meters), with no fish ever being observed beyond 27,349 feet (8,336 meters).[9][10]

References

  1. ^ Paul H. Yancey (2005). "Organic osmolytes as compatible, metabolic and counteracting cytoprotectants in high osmolarity and other stresses". Journal of Experimental Biology. 208 (15): 2819–2830. doi:10.1242/jeb.01730. PMID 16043587.
  2. ^ Review of Medical Physiology, William F. Ganong, McGraw-Hill Medical, ISBN 978-0-07-144040-0.
  3. ^ Bolen DW, Baskakov IV (2001). "The osmophobic effect: natural selection of a thermodynamic force in protein folding". Journal of Molecular Biology. 310 (5): 955–963. doi:10.1006/jmbi.2001.4819. PMID 11502004.
  4. ^ author, Su, Zhaoqian (2017). Roles of cosolvents on protein stability. OCLC 1245504372. ((cite book)): |last= has generic name (help)CS1 maint: multiple names: authors list (link)
  5. ^ Neuhofer, W.; Beck, F. X. (2006). "Survival in Hostile Environments: Strategies of Renal Medullary Cells". Physiology. 21 (3): 171–180. doi:10.1152/physiol.00003.2006. PMID 16714475.
  6. ^ a b Arakawa T, Timasheff SN (1985). "The stabilization of proteins by osmolytes". Biophysical Journal. 47 (3): 411–414. Bibcode:1985BpJ....47..411A. doi:10.1016/s0006-3495(85)83932-1. PMC 1435219. PMID 3978211.
  7. ^ Csonka LN (1989). "Physiological and genetic responses of bacteria to osmotic stress". Microbiology and Molecular Biology Reviews. 53 (1): 121–147. doi:10.1128/mr.53.1.121-147.1989. PMC 372720. PMID 2651863.
  8. ^ Gallazzini, M.; Burg, M. B. (2009). "What's New About Osmotic Regulation of Glycerophosphocholine". Physiology. 24 (4): 245–249. doi:10.1152/physiol.00009.2009. PMC 2943332. PMID 19675355.
  9. ^ Yancey PH, Gerringer ME, Drazen JC, Rowden AA, Jamieson A (2014). "Marine fish may be biochemically constrained from inhabiting the deepest ocean depths". PNAS. 111 (12): 4461–4465. Bibcode:2014PNAS..111.4461Y. doi:10.1073/pnas.1322003111. PMC 3970477. PMID 24591588.
  10. ^ Lu, Donna (3 April 2023). "Scientists find deepest fish ever recorded at 8,300 metres underwater near Japan". The Guardian. London. Retrieved 25 May 2023.

Further reading


Categories