Elements of Life Study Guide


Approximately 115 elements are known to humans and can be easily encountered in the periodic table. But only 19 out of them are vital for the survival of humans. These elements are essential and have a general trend to be restricted to the first four rows of the periodic table (molybdenum and iodine being the exception).

However, these elements may be indispensable for the nutrition of some specific organisms. For instance, bromine is abundant in marine species, and tungsten is required to survive several microbes.

What makes these elements essential?

Essential elements are necessary for maintaining balance in life. For example, if a deficiency of any important element continuously causes aberrant growth or functioning, dietary supplementation of that element prevents this from occurring. Thus, the element is regarded as vital/essential. However, if an organism develops typically on a diet with low Vitamin E, it is not considered essential for that specific organism.

Basic elements required in the human body

99% percent of the mass of the human body is made up of CHNOPS (hydrogen, oxygen, nitrogen, carbon, phosphorus, and sulfur). In plants, carbon, hydrogen, and oxygen (macromolecules) are mostly received from CO₂ and H₂O. Carbon makes up 17.5%, oxygen makes up 25.6%, nitrogen makes up 2.4%, and hydrogen 10.2%.


  • Carbon atoms have the unique ability to create lengthy chains and rings by connecting.
  • This ability permits carbon to build many stable compounds with distinct molecular structures and still be closely related.
  • Biological molecules such as carbohydrates, proteins, lipids, and nucleic acids are composed of carbon molecules.


  • Hydrogen is the perfect stability provider to carbon atoms.
  • Because of the existence of C—H bonds, a considerable section of the carbon chain is rendered unreactive.
  • Hydrogen aids in the production of energy in the human body. As we all know, ATP (Adenosine triphosphate) is the main source of energy for most cellular processes.
  • We eat carbs, which are made up of carbon, hydrogen, and oxygen, and provide energy.


  • Oxygen is what keeps us alive.
  • The energy released by the cells requires aerobic respiration to release chemical energy to our organs and tissues.
  • It is believed that 90% of our biochemical and metabolic activities need oxygen.


One aspect of biological molecules that is extremely significant is the presence of functional groups. Functional groups are collections of atoms that attach to the carbon skeleton of an organic molecule and confer specific properties. Since many biological molecules have long chains, they can take on an almost endless range of forms.

The Amino Group:

Nitrogen atomSource

  • This tasteless gaseous element that makes up 75% (by weight) of the earth’s atmosphere is vital for protein synthesis and producing numerous nitrogenous compounds like hormones and neurotransmitters.
  • The functional group is called the Amino Group: Nitrogen bonded to two hydrogens and one carbon atom.
  • Nitrogen is an important component of DNA and other nucleic acids, the major component of chromosomes, and a carrier of genetic information.
  • The genetic information is carried by DNA.
  • Even in plants, nitrogen is one of the major constituents of proteins, nucleic acids, vitamins, and hormones.

The Phosphate Group:

Phosphorus atomSource

  • Bones, teeth, DNA, and RNA are all made up of phosphorus.
  • Phosphorus is also a part of the cell membrane structure in the form of phospholipids and the body’s primary source of energy, ATP.
  • The phosphate ion covalently attaches to the carbon skeleton to form the functional phosphate group.
  • Phosphorus is essential for gene transcription, enzyme activity, maintaining a proper pH in extracellular fluid, and intracellular energy storage.
  • Phosphorus is found in cell membranes, proteins, and all nucleic acids and nucleotides in plants, and it is essential for all phosphorylation reactions.

The Sulfhydryl Group:

  • This eighth most abundant element in humans helps create amino acids that are used to create protein, the building blocks of our body.
  • Sulfur also plays an important role in detoxification. It aids in the safe digestion of medications, dietary chemicals, and even hazardous metals by the human body.
  • In plants, sulphur is found in two amino acids, cysteine and methionine, and is a key component of various coenzymes, vitamins (thiamine, biotin, coenzyme A), and ferredoxin.
  • The sulfhydryl group is the functional group that includes sulfur bonded to a hydrogen atom and can form cross-links with other sulfhydryl groups.

The Hydroxyl Group:

  • This group is found in sugars and alcohol. Hydrogen bonded to Oxygen (OH) attached to the carbon skeleton helps in forming hydrogen bonds with water.
  • This property confers on the molecule hydrophilicity and increases the solubility of molecules containing them.

The Carbonyl Group:

  • A carbonyl group is a functional group where a carbon atom is double-bonded to an oxygen atom.
  • There are two groups: One group is composed of the aldehydes and ketones, the other is composed of the carboxylic acids and their derivatives.
  • If a hydrogen atom is attached to the carbon-oxygen double bond, it’s called an aldehyde. A ketone’s carbonyl group does not have hydrogen. Molecules containing the carbonyl group are polar.

The Carboxyl Group:

  • The carboxyl group is a combination of carbonyl and hydroxyl functional groups.
  • Carbon double-bonded to oxygen and hydroxyl bestows unique properties of each individual group.
  • Carboxyl groups are polar and make good acids and are found in the amino acids used to build proteins.


  • Elements are the chemically pure substances included in the periodic table.
  • We are made and surrounded by elements and the use of these elements.
  • Hydrogen and carbon are two essential elements that affect life forms, among many others.
  • Functional groups include amino, phosphate, hydroxyl, carbonyl, carboxyl, and sulfhydryl groups.


1. What are the 5 main elements of life?

Everything in nature is made up of 5 elements of life, according to the five elements theory: Earth, Water, Fire, Air, and Space. However, chemistry answers this with carbon, hydrogen, nitrogen, oxygen, and sulfur.

2. What are the 21 elements essential for life?

Calcium, carbon, chlorine, cobalt, copper, fluorine, hydrogen, iodine, iron, magnesium, manganese, molybdenum, nitrogen, oxygen, phosphorus, potassium, selenium, sodium, sulfur, and zinc are regarded as the 21 elements essential for life.

3. What are the six elements of life, and how can we get them?

CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur) are the six elements of life and can be found in the form of natural resources in any of the three states.

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  1. Mineral nutrition https://ncert.nic.in/textbook/pdf/kebo112.pdf. Accessed 16 Dec, 2021.
  2. Biology Elements of Life – Carbon. https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/1.9/related/lecture/biology-elements-of-life-carbon/. Accessed 16 Dec, 2021.
  3. The Basic Elements of Life’s. https://thescipub.com/abstract/ajeassp.2016.1189.1197. Accessed 16 Dec, 2021.
  4. How six elements came together to form life on Earth. https://blog.oup.com/2019/02/how-six-elements-form-life-earth/. Accessed 16 Dec, 2021.

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