Monday, August 5, 2013

Quick Overview of the Organic Molecules of Life

3D Render of Glucose Molecule; credit: wikimedia

There are four groups of molecules that make up living organisms from the single celled prokaryotes to complex eukaryotes. These are carbohydrates, proteins, lipids and nucleic acids.


These consist of the simple sugars (monosaccharides), disaccharides which are two monosaccharides joined  together by covalent bond and polysaccharides which consist of many monosaccharides bonded together.

Common Monosaccharides
  • Galactose: A source of energy for living organisms
  • Ribose: Found in RNA
  • Glucose: A source of energy for living organisms
  • Fructose: A source of energy for living organisms
 Common Polysaccharides
  • Chitin: Used by arthropods to build their exoskeletons
  • Starch: Used by plants for storage of sugars
  • Glycogen: Used by animals for storage of sugars
  • Cellulose: Plants use this to build their cell walls


The defining trait of all lipids is that they do not mix well with water. This is due to the fact that their molecular structure contains mostly regions of hydrocarbons.
  • Phospholipids: These are what cell membranes are made of
  • Fats: Their main purpose is energy storage, although fat cells also serve to protect organs and provide insulation
  • Steroids: These are often used to create hormones in the body or are components in cells (an example being cholesterol)


These molecules are responsible for countless functions in living organisms. They can be used for everything from storage and structure to defense of our bodies. Here are a few examples:
  • Insulin: Transmits a signal to stop the release of glucagon thereby regulating blood sugar levels
  • Lactase: This is an enzyme, used in the digestion of milk
  • Keratin: A group of structural proteins found in human skin, hair and fingernails as well as other animals.
  • Antibodies: A protein produced by our immune systems that helps identify viruses and bacteria.
  • Hemoglobin: Used to transport oxygen throughout the body
  • Actin: This forms microfilaments found in eukaryotic cells, and is used in cell movement, muscle contraction and cell division to name just a few.
  • Histones: Proteins that package DNA into structural units to form chromosomes.

Nucleic Acids

These provide the blueprints for all living organisms in the form of DNA and RNA.
  • Deoxyribonucleic acid (DNA): Contains the genetic instruction, which is passed along through each generation, for the growth and maintenance of all living organisms and some viruses.
  • Ribonucleic acid (RNA): Can also carry genetic information as is the case of some viruses, but in more complex organisms, typically performs the tasks of gene expression

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