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1.2 Elements of Life






⏱️  3 min read

written by

Danna Esther Gelfand

danna esther gelfand

September 18, 2020

Organisms, such as ourselves, are made up of matter, which takes up space and has mass. The matter is made up of elements, which are substances that cannot be broken down further by chemical reactions. Example: C (Carbon), and O (Oxygen). Essential elements to know: O, C, H, N, Ca, P, K, S, Na, Cl, and Mg.

Compounds are substances that can be broken down further by chemical reactions because they are made of two or more elements that are in a fixed ratio to each other. (e.g H20 which is two hydrogens and one oxygen).


An element's properties are retained by the smallest unit of mass called an atom. The subatomic particles that make up atoms are: protons (positive charge), neutrons (neutral/no electrical charge), and electrons (negative charge).

The atomic number is determined by the number of protons in the nucleus (in the figure below, the number 6 is the atomic number of Carbon). The atomic mass number is the sum of the protons and neutrons in the nucleus (in the figure below, the number 12.011 is the Atomic Mass number for Carbon).

Image courtesy of ABCTeach.


Isotopes are two atoms of an element that have a different number of neutrons. Radioactive Isotopes are present in dating fossils, diagnosing disorders, etc. They decay spontaneously and release energy. Example: Carbon-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.

Electron Shells

An electron's potential energy (location/structure) is called an energy level or electron shell. When electrons absorb energy they move up an energy level farther away from the nucleus. When electrons release the energy they move closer to the nucleus.


Carbon is the building block of the major macromolecules/organic molecules: carbohydrates, lipids, proteins, and nucleic Acids. It stores compounds and forms cells in organisms like us!

Reasoning: Carbon has the unique ability to form 4 covalent bonds (tetra-valence). The goal for all atoms is to be stable. Carbon must find four more electrons to fill its outer shell, giving a total of eight and satisfying the octet rule. The octet rule states that atoms will lose, gain or share electrons to achieve an electron configuration of 8 valence electrons. (e.g CH4 methane)

Functional Groups

Functional Groups are accessory elements that give molecules a different structure, therefore, a different function. They can be classified as hydrophobic or hydrophilic based on their charge and polarity characteristics.

  • Hydroxyl Group: Hydrogen bonded to Oxygen (OH) attached to the carbon skeleton. (alcohols such as methanol, polar)

Image courtesy of WikiMedia Commons.

  • Carbonyl Group: Double bond (sharing of two pairs of valence electrons) between carbon and oxygen. If it's on the end of the carbon skeleton, it’s called an aldehyde. If not then it is a ketone. (polar)

Image courtesy of WikiMedia Commons.

  • Carboxyl Group: a combination of carbonyl and hydroxyl. Carbon double-bonded to an oxygen and a hydroxyl. (release H+ into solutions, acidic)

Image courtesy of WikiMedia Commons.

  • Amino Group: Nitrogen bonded to two hydrogens and one carbon atom. Amines are organic molecules that have an amino group. (remove H+ from solutions therefore basic) Nitrogen is used to build proteins and nucleic acids.

Image courtesy of WikiMedia Commons.

  • Phosphate Group: phosphate ion covalently attached to the carbon skeleton. (Lots of energy.used to make nucleic acids and phospholipids, acidic because they release H+ into solutions)

Image courtesy of WikiMedia Commons.

  • Sulfhydryl Group: Sulfur bonded to a hydrogen atom. (Polar)

**(In the images above, the R represents an unknown part of the molecule that the functional group is attached to)**

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