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Life Science: Session 1

Organic Molecules

What is the nature of living matter?

Levels of Organization
Organic Molecule

Like all matter, life is built from atoms — the basic units of matter that link together to form molecules. Organic molecules are the molecules of life and are built around chains of carbon atoms that are often quite long. There are four main groups of organic molecules that combine to build cells and their parts: carbohydrates, proteins, lipids, and nucleic acids.

What makes carbon so unique?

Each carbon atom can form strong, stable bonds with four other atoms at a time – these are usually oxygen, hydrogen, nitrogen, sulfur, and phosphorus atoms. Carbon can also bond to other carbon atoms to form chains that are almost unlimited in length. This creates a huge number and variety of molecules that can be built from carbon atoms. No other element even comes close. Organic chemistry is the study of these carbon-based molecules.

In addition to composing living matter, organic molecules are found in the nonliving world. Fossil fuels, which are derived from the buried remains of once-living organisms, are made of organic molecules. So are many man-made compounds, such as plastics, pesticides, and many medicines. The clothes we wear are all made of organic molecules: wool, silk, cotton, polyester, nylon, acrylic, and rayon. Many household and personal goods are organic as well, including detergent, cleaners, soap, shampoo, and perfume.

How does living matter compare to nonliving matter?

Although there are some exceptions, most naturally occurring nonliving things are made of inorganic molecules. Inorganic molecules are not composed of chains of carbon atoms and are generally much less complex. Living things do use inorganic molecules—like water, oxygen, and carbon dioxide—and their atoms may even be assimilated into organic molecules. Plants, for example, use carbon dioxide with the carbon being assimilated into a carbohydrate: sugar.

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