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Biology LibreTexts

3: Structure & Function

Function flows from structure. In order to understand the function of biomolecules, we must first understand their structures.

  • 3.0: Introduction to Structure & Function
    If we hope to understand function in biological systems, we must first understand structure.
  • 3.1: Building Blocks
    Biological macromolecules are all polymers of a sort, even fats, in which the fatty acids can be thought of as polymers of carbon. The remaining categories of biological macromolecules include proteins, nucleic acids, and polysaccharides. The building blocks of these, respectively, are amino acids, nucleotides, and monosaccharides (sugars). Of these, the most diverse collection of chemical properties is found among the amino acids.
  • 3.2: Proteins
    Whereas nucleotides all are water soluble and have the same basic composition (sugar, base, phosphate) and the sugars also are water soluble and mostly contain 5 or 6 carbons (a few exceptions), the amino acids (general structure below) are structurally and chemically diverse.
  • 3.3: Nucleic Acids
    The DNA molecule is a polymer of nucleoside monophosphates with phosphodiester bonds between the phosphate and the 5’ end of one deoxyribose and the 3’ end of the next one. In the B form the DNA helix has a repeat of 10.5 base pairs per turn, with sugars and phosphate forming the covalent “backbone" of the molecule and the adenine, guanine, cytosine, and thymine bases oriented in the middle where they form the now familiar base-pairs that look like the rungs of a ladder.
  • 3.4: Carbohydrates
    The last class of macromolecules we will consider structurally here is the carbohydrates. Built of sugars or modified sugars, carbohydrates have several important functions, including structural integrity, cellular identification, and energy storage.
  • 3.5: Lipids and Membranes
    Lipids are a broad class of molecules that all share the characteristic that they have at least a portion of them that is hydrophobic. The class of molecules includes fats, oils (and their substituent fatty acids), steroids, fat-soluble vitamins, prostaglandins, glycerophospholipids, and sphingolipids. Interestingly, each of these can be derived from acetyl-CoA.

Thumbanil: An antibody molecule. The two heavy chains are colored red and blue and the two light chains green and yellow. Image used with permission (Public Domain; TimVickers).