Although living cells are primarily made up of water, a number of other molecules are also abundant. Gigantic molecules, called macromolecules, populate a cell and provide it with important functions for life. For example, macromolecules provide structural support, a source of stored fuel, the ability to store and retrieve genetic information, and the ability to speed biochemical reactions. Four major types of macromolecules—proteins, carbohydrates, nucleic acids, and lipids—play these important roles in the life of a cell. In this tutorial, we examine the structures and functions of nucleic acids and proteins.


A macromolecule's structure is intimately connected with its function. Consider a nucleic acid. This type of polymer is made up of a chain of nucleotides that are strung together in a precise sequence. The nucleotide sequence provides a code that stores genetic information and that the cell can copy and pass on to the next generation of cells.

In a similar way, the precise sequence of monomers (amino acids) in a protein also acts as a kind of code. In this case, the amino acid sequence determines the protein's 3-dimensional shape and chemical reactivity, which, in turn, endow a protein with its specific function. Some proteins, for example, have shapes that allow them to grab molecules and speed chemical reactions. Others, such as strong cables of collagen, provide structural support to cells and tissues.

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Textbook Reference: Concept 3.1 Nucleic Acids Are Informational Macromolecules