Essential Elements in a Biological System and their Role

What are the essential elements in a biological system ?

As the name suggests, elements that are essential or necessary for the life process are called essential elements. For example, Oxygen, Carbon, Hydrogen, Nitrogen, etc.

Metals like Ca, Ni, Co, Zn, etc. are responsible for initiating or inhibiting reactions in biological systems. That's why in bioinorganic chemistry we investigate these metals in terms of their nutrition, toxicity, storage, and transport in biological systems.

These elements are a must for normal growth and reproduction in living organisms and cannot be replaced by other elements. So, the following are some common essential elements that are found in humans and plants.

1. Calcium (Ca)

Calcium is a critical essential element in all animals and human beings. A healthy human adult has about 1.05 Kg of calcium, out of which 99% exists as phosphates, resembling the mineral hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] in bones and teeth.

Calcium source milk

The small remainder of calcium is found in cellular fluids, existing in partly ionized or protein-bound forms. Calcium can be obtained from primary dietary sources like milk (65-76 %), eggs (5-10 %), fish and meat. It is also found in non-dairy foods like nuts, fruits, beans, etc. but in very less amount.

Role of calcium in the biological system

  1. Calcium plays a vital role in performing the body's basic functions like blood circulation, moving of muscles, and releasing of hormones.
  2. Calcium acts as an intracellular messenger which helps to carry messages from the brain to other parts of the body.
  3. Calcium plays a significant role in the metabolism of nitrogen in plants. The absence of this mineral in the plants affects the size and number of chloroplasts.
  4. Extracellular calcium is important for maintaining potential differences across cell membranes.

Deficiency of calcium

  1. Deficiency of calcium can increase the chances of getting osteoporosis and porous bones that can easily fracture.
  2. Calcium helps in blood clotting. So, its deficiency can increase the blood clotting time.
  3. Deficiency of calcium hampers the growth and development in children who don't get enough calcium may not grow to their full potential height.
  4. Its deficiency also leads to disorder of nerves.

Excess of calcium

  1. Excess of calcium leads to the formation of stones, hardening of arteries, and cataracts in the eyes because when the excess calcium comes into the blood, it is rejected by cells and its salt is not soluble.
  2. Excess calcium can interfere in the waking of the brain, resulting in confusion, lethargy, and fatigue.
  3. Excess calcium can also increase the chances of getting heart diseases like cardiac arrhythmia.
  4. Excess calcium can cause general problems like upset stomach, nausea, vomiting, and constipation.

2. Magnesium (Mg)

Magnesium is an essential element in the biological system which occurs typically as an Mg⁺² ion. It is an essential element for life and present in every cell of organisms. An average human has 35 mg, out of which 99% is either intercellular or it is present in bones.


It can be obtained from dietary sources like nuts, seafood, legumes, and vegetables.

Role of Magnesium in biological systems

  1. Magnesium act as a cofactor in all enzymatic reaction in animals that are catalyzed by ATP (Adenosine Triphosphate)
  2. Magnesium is responsible for oxidative phosphorylation, DNA transcription, RNA function, protein synthesis, and critical cell membrane functions.
  3. Magnesium helps to maintain a healthy electrolytic balance in our body.
  4. In plants, Magnesium is necessary for the synthesis of chlorophyll and photosynthesis.

Deficiency of Magnesium

  1. Magnesium deficiency in plants destroys the green color of leaves.
  2. Magnesium deficiency can cause life-threatening complications like seizures, cardiac arrhythmias, sudden death, etc.
  3. Magnesium deficiency can cause mental disorders such as mental numbness, delirium, and coma.
  4. Magnesium deficiency in humans is indicated by cramps and swelling of arterial walls.

Excess of Magnesium

  1. Excess Magnesium in the body is known as hypermagnesemia. It increases Magnesium concentration in the blood which leads to chronic kidney disease.
  2. High level of Magnesium in the blood can also cause heart problems, difficulty in breathing, and shock.
  3. Its overdose can cause general problems like nausea, vomiting, headache, and hypotension.

3. Sodium (Na)

Sodium is an essential element in the biological system which occurs typically as Na⁺ ion. It is the main extracellular cation in all animals including human beings. An average human body contains 105 g sodium, out of which 24% is present in bones and 65% is present in extracellular fluid.

Sodium source salt

Sodium is obtained from Sodium chloride (NaCl) in our diet. Other food items like buttermilk, cottage cheese, Butter, etc. also contain an acceptable amount of sodium.

Role of Sodium in the biological system

  1. Sodium is essential for the formation of HCl (Hydrochloric acid) in the stomach and conduction of nerve and muscle contraction.
  2. Sodium also helps in maintaining the osmotic pressure of the body fluid, thereby protecting the body against fluid loss.
  3. Na⁺ ion is responsive for the transport of glucose and amino acid in the cell.
  4. Sodium plays important role in the presentation of permeability of the cell.

Deficiency of Sodium

  1. Due to high environmental temperature extreme sweating may cause loss of sodium ion levels in the body which leads to muscular cramps of the abdomen and headaches.
  2. Deficiency of Sodium can cause loss of consciousness, seizures, and coma.
  3. Low sodium count in the body can cause common problems like dizziness, malaise, nausea, bloating, etc.

Excess of Sodium

  1. Excessive intake of Na⁺ ions results in elevated blood pressure (hypertension).
  2. The saline water containing an excessive amount of NaCl is harmful to plants and aquatic life because of the toxicity of Na⁺ ions.
  3. Our body holds water to compensate for the high Sodium levels. This results in increased water retention which results in swelling of different parts of the body.
  4. Some studies show that excessive Sodium levels in the body cause stiffening of blood vessels and arteries. This may result in a higher risk of heart disease and premature death.

4. Potassium (K)

Potassium is an essential element in the biological system which occurs typically as a K⁺ ion. It is mainly present in the intracellular and extracellular fluids of the body. An average human body contains 140 g of Potassium, out of which 90% is both intracellular and exchangeable.

Potassium source banana

Potassium is obtained from primary dietary sources like vegetables that include broccoli, peas, tomatoes, potatoes, and fruits like cantaloupe, bananas, kiwi, etc.

Role of Potassium in the biological system

  1. It plays a vital role in metabolic functions, protein synthesis, and enzyme activity.
  2. It contains osmotic pressure and water retention.
  3. It regulates acid-base equilibrium.
  4. K+ ion is essential for nerve impulse and muscle retention.

Deficiency of Potassium

  1. Potassium helps to regulate muscle contractions. So, when potassium levels are low in the blood, it may result in sudden cramps and uncontrolled muscle contraction.
  2. Potassium deficiency can slow the movement of food through the digestive system which causes problems like bloating and constipation.
  3. Potassium helps to regulate heartbeat. So, its deficiency can cause problems like irregular heartbeat, heart palpitations, and arrhythmia.
  4. Potassium helps the lungs to expand and contract. So, its deficiency may result in shortness of breath or even lung failure, which is fatal.

Excess of Potassium

  1. Excess Potassium, may prove toxic to mammals when injected intravenously.
  2. High Potassium level can cause kidney failure because when kidneys don't function properly, they can remove extra potassium from the body which leads to potassium buildup.
  3. Excess potassium can cause various general problems like dehydration, internal bleeding, and Type 1 diabetes.
  4. Excess Potassium can affect arteries and veins and can cause a heart attack.

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