Elements necessary for humans

At present there are 118 elements listed in the periodic table. Some of these elements are commonly found on the earth in the form of ores. Some are radioactive and have very short half lives. Many such elements have been synthesized in the laboratory and live for a very short time.

Human body like other things existing is made of compounds which are made from the elements. Out of these 118 only some elements are connected with the human body. Although elements as such don’t make up the body it is the combined form that is molecules constitute the human body. But elemental composition is as follows by mass.

Oxygen: 65%

Carbon: 18%

Hydrogen: 10%

Nitrogen: 3%

Other elements: 4%

Other elements include Calcium, Potassium, Phosphorus, Sulphur, Sodium, Chlorine, Magnesium, Boron, Chromium, Cobalt, Copper,  Fluorine, Iodine, Iron, Manganese, Molybdenum, Selenium, Silicon, Tin, Vanadium and Zinc. Although these elements are used in very minor amount, they are crucial to some body processes. These are micronutrients.

An element can perform one or many functions in the body. Elements roles are defined as follows:

Building Blocks

The main building blocks of the body are proteins which are synthesized from amino acids. For these elements used are Hydrogen, Carbon, Nitrogen, Oxygen, Phosphorus and Sulphur. DNA also contains these elements except Sulphur. DNA is the genetic code which encodes the instructions.


Enzymes are chemicals which are catalysts for carrying out chemical reactions like breakdown of sugars and other macro molecules. Such enzymes use some elements like Magnesium, Manganese, Copper, Zinc, Selenium and Molybdenum. Enzymes play role in respiration, digestion, metabolism and immune system.

Nerves and Control

Brain sends messages to different parts of the body and this is a two way communication. Electrical signals are carried through electrolytic solutions like brines. Sodium, Potassium and Calcium ions this play the role of transmitting the signals. Similarly Chloride ions regulate the water in and out of cells. Iodine is used to make hormones which regulate metabolism.

Bones and Teeth

Bones make the template on which our body is hoisted. Strong bones and teeth are essential for the healthy body.  Bones and Teeth are made of Calcium and phosphate. Phosphate contains Phosphorus and Oxygen. Manganese element makes more stronger and resistance to breaking.


Blood is the lifeline of the body. Blood carries oxygen to the cells and removes the carbon-dioxide gas which is the byproduct of combustion reaction. Oxygen is carried by blood due to the presence of iron which binds the Oxygen. Other elements which are constituents of blood are Carbon, Oxygen, Iron and Cobalt. Cobalt is essential to make red blood cells.

Respiration and Energy

Respiration is inhalation of Oxygen. Adenosine Triphosphate (ATP) is formed during respiration which is the compound used by body as energy. Main elements involved here are Carbon, Nitrogen, Phosphorus and Oxygen. Most prominent sources of energy are Carbohydrates and Fats which contain Carbon, hydrogen and Oxygen elements.

Source: c&en magazine of American Chemical Society (ACS)

Our Body is a Wonder Machine

Photosynthesis is the process by which plants make two essential things on which the very survival of animals is hinged. These are namely a sugar called Glucose and oxygen. In the beginning oxygen was a poison to many microbes. But since it was a question of survive or perish, slowly they adapted to respiration using oxygen. Those which could not change receded to great depth where oxygen cannot reach.

Glucose is a like a charged battery which stores energy. Where does this energy come from? Obviously it is the Sun on which the life on the Earth is based upon. Plants use carbon dioxide and water and a mediator called chlorophyll to make glucose and oxygen. Anyone familiar with thermodynamics knows that this reaction is not favorable as its overall Gibbs free energy is positive. Second law of thermodynamics requires that only those reactions are spontaneous for which this energy change is negative. In simple words the energy of products should be lower than that of reactants. Here the energy content of the products is higher by 2880 Kilo Joules per mole. It is the Sun who provides this energy and plants store it in the glucose.

Many of the reactions that take place in living organisms require a source of free energy to drive them. The immediate source of this energy in heterotrophic organisms, which include animals, fungi, and most bacteria, is the sugar glucose. Now reverse reaction that is the oxidation of glucose to carbon dioxide and water takes place when animals consume glucose and oxygen. Thus 2880 KJ/mole energy is liberated.

Of course it would not do to simply “burn” the glucose in the normal way; the energy change would be wasted as heat, and rather too quickly for the well-being of the organism! Effective utilization of this free energy requires a means of capturing it from the glucose and then releasing it in small amounts when and where it is needed. This is accomplished by breaking down the glucose in a series of a dozen or more steps in which the energy liberated in each stage is captured by an “energy carrier” molecule, of which the most important is adenosine diphosphate, known shortly as ADP. At each step in the breakdown of glucose, an ADP molecule reacts with inorganic phosphate and changes into adenosine triphosphate ATP

The 30 kJ mol–1 of free energy stored in each ATP molecule is released when the molecule travels to a site where it is needed and loses one of its phosphate groups, yielding inorganic phosphate and ADP, which eventually finds its way back the site of glucose metabolism for recycling back into ATP. The complete breakdown of one molecule of glucose is coupled with the production of 38 molecules of ATP according to the overall reaction

For each mole of glucose metabolized, 38 × (30 kJ) = 1140 kJ of free energy is captured as ATP, representing an energy efficiency of 1140/2880 = 0.4. That is, 40% of the free energy obtainable from the oxidation of glucose is made available to drive other metabolic processes. The rest is liberated as heat.

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