Electrolytes exist as salts which dissociate into charged particle ions once dissolved in water, which allow for an electrical current to be carried through water (Gropper & Smith, 2013). Water follows electrolyte movement across the selectively permeable cell membrane walls (Gropper & Smith, 2013). Electrolytes reside both inside and outside cells and carry both positively and negatively charged ions. Sodium and chloride are known as extracellular electrolytes as they are primarily housed outside the cell. Potassium, magnesium, phosphate and sulfate function as intracellular electrolytes housed primarily inside the cell (Gropper & Smith, 2013).
Sodium is the most abundant cation within the body and plays key roles in the maintenance of fluid balance, impulse conduction, transmission and even muscle contraction (Gropper & Smith, 2013). It has a large effect on plasma osmolarity and is he most abundant electrolyte in sweat (Evans, James, Shirreffs, & Maughan, 2017). Chloride, being the most abundant anion, is utilized in the maintenance of electrolyte balance and in the formation of gastric hydrochloric acid, and also during phagocytosis in the contribution of destruction of foreign compounds (Gropper & Smith, 2013). Phosphate/ phosphorus has a number of functions and mechanisms of actions which include: bone mineralization, nucleotide/nucleoside phosphates, as a component of cell membranes, acid-base balance and in oxygen delivery (Gropper & Smith, 2013). Magnesium plays a wide variety of functions such as glycolysis, TCA cycle, pentose phosphate pathways, creatine phosphate formation, b-oxidation, nucleic acid synthesis, DNA synthesis and degradation, and replication and transcription. Potassium exists as the greatest cation within intracellular fluid (Evans et al., 2017). Unlike sodium, it is lost in small amounts of sweat and therefore does not cause significant health concerns such as low sodium levels, a condition known as hypokalemia (Evans et al., 2017).
References
Evans, G.H., James, L.J., Shirreffs, S.M., & Maughan, R.J. (2017). Optimizing the restoration and maintenance fluid balance after exercise-induced dehydration. Journal of Applied Physiology, 122, 945-951. Retrieved from https://www.physiology.org/doi/full/10.1152/japplphysiol.00745.2016
Gropper, S.S., & Smith, J.L. (2013). Chapter 11: Major minerals & Chapter 12: Water and electrolytes. Advanced nutrition and human metabolism (6th ed.)(pp.425-473). Belmont, CA:Wadsworth Cengage Learning
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