Sodium in biology

They are responsible for the co-transport of glucose in the sodium glucose symport, are used to help maintain membrane polarity with the help of the sodium potassium pump, and are paired with water to thin the mucus of the airway lumen when the active Cystic Fibrosis Transport Receptor moves chloride ions into the airway.

[4] The minimum physiological requirement for sodium is between 115 and 500 mg per day depending on sweating due to physical activity, and whether the person is adapted to the climate.

[8] In C4 plants, sodium is a micronutrient that aids in metabolism, specifically in regeneration of phosphoenolpyruvate (involved in the biosynthesis of various aromatic compounds, and in carbon fixation) and synthesis of chlorophyll.

[17] In others, it substitutes for potassium in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata.

Relative loss of body water will cause sodium concentration to rise higher than normal, a condition known as hypernatremia.

Conversely, an excess of body water caused by drinking will result in too little sodium in the blood (hyponatremia), a condition which is again sensed by the hypothalamus, causing a decrease in vasopressin hormone secretion from the posterior pituitary, and a consequent loss of water in the urine, which acts to restore blood sodium concentrations to normal.

Severely dehydrated persons, such as people rescued from ocean or desert survival situations, usually have very high blood sodium concentrations.

These must be very carefully and slowly returned to normal, since too-rapid correction of hypernatremia may result in brain damage from cellular swelling, as water moves suddenly into cells with high osmolar content.

Nitric oxide (NO) contributes to vessel homeostasis by inhibiting vascular smooth muscle contraction and growth, platelet aggregation, and leukocyte adhesion to the endothelium.

The sodium-potassium pump works with the sodium and potassium leak channels to maintain the membrane potential between the cell and the extracellular space.

[4] The sodium-potassium pump plays a large role in neural signaling due to the maintenance of cell membrane potential.

[24] When the pump fails to function, patients are susceptible to illnesses like heart failure and chronic obstructive lung disease (COLD).

[25] In COLD diagnoses, a majority of patients found to have a lowered amount of magnesium and potassium also had a decreased concentration of the sodium-potassium pump in skeletal and smooth muscle during respiratory failure.

In cases of Cystic Fibrosis, the CFTR is defective and only binds a single ATP, leading to the channel failing to open and preventing chloride ions from diffusing into the airway lumen.

The sodium–potassium pump , a critical enzyme for regulating sodium and potassium levels in cells
Here is a hand-drawn depiction of a membrane bound sodium-potassium pump and sodium and potassium ion channels can be seen along with the directed movement of the ions indicated by arrows.
The sodium-glucose symporter is initially opened to the extracellular matrix. Once 2 sodium and the glucose bind, the conformation closes to the extracellular matrix and opens to the cytosol where the sodium and glucose are released. The confirmation of the symporter than returns to the initial confirmation.
Pictured on the left is the working CFTR where the ions are able to move through the cells and the mucus is thinned out. On the right is a not functioning CFTR that prevents the movements of ions and causes thicker mucus in the airway lumen.