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Molecules of Life



All living things on Earth share basic characteristics and require similar molecules of life to survive and carry out the functions of life. Water is essential for life. Although some species can survive long, dry periods, every organism needs water to live. Organisms rely on a class of molecules containing carbon, called organic molecules. Among these organic molecules are the nucleic acids that provide the genetic material to the cell, proteins that control the cell's functions and provide structure, carbohydrates that give the cell energy, and lipids that enclose the cell. Furthermore, cells regulate their internal pH, which indicates how acidic or basic the cell is.

At A Glance

  • Living things consist of water, carbon (organic) molecules, acids, and bases.
  • Living things require water to carry out life's functions, such as moving materials into and out of cells and keeping cool.
  • Life on Earth is built on carbon-containing compounds.
  • Nucleic acids provide instructions for making organisms and building and maintaining cells.
  • Proteins assist chemical reactions, transport materials into and out of cells, and provide structure.
  • Carbohydrates provide energy for cells.
  • Lipids make up cell membranes and are used as energy storage.
  • Living things maintain a near-neutral pH. The pH of a solution indicates how acidic or basic the solution is. Buffers resist changes in pH.