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Biology LibreTexts

2: Basic Cell Chemistry - Chemical Compounds & their Interactions

  • Page ID
    16099
    • 2.1: Water
      There is no life without water. In this chapter, water will be used to review some very basic ideas in chemistry, particularly as applies to cell and molecular biology.
    • 2.2: Acids and Bases
      The release of H+ and OH— are not limited to water molecules, and many compounds do so in aqueous solutions. These compounds can be classified as acids (raising the free H+ concentration) or bases (increasing the free hydroxyl concentration]. The extent to which acids and bases donate or remove protons is measured on the pH scale, which is a logarithmic scale of relative H+ concentration.
    • 2.3: Carbon
      The major constituent molecules in all living organisms are based on carbon. Carbon has versatility stemming from its four outer shell electrons, allowing the possibility of four covalent bonds with a variety of partners, including very stable carbon-carbon covalent bonds. Because of this, long carbon chains can form the backbone of more complex molecules and makes possible the great diversity of macromolecules found in the cell.
    • 2.4: Sugars
      Sugars, and glucose in particular, are important molecules for cells because they are the primary energy source. Sugars have the general chemical formula CH₂O and can be joined together almost infinitely for storage. However, because they are hydrophilic, they allow water molecules to intercalate between them, and cannot pack as efficiently as fats, which are hydrophobic and thus exclude water. On the other hand, the sugars can be mobilized for use more quickly.
    • 2.5: Nucleotides
      Nucleotides, the building blocks of RNA and DNA, are themselves composed of a pentose sugar attached to a nitrogenous base on one side and a phosphate group on another. The sugar is either the 5-carbon sugar ribose or its close cousin, deoxyribose (the “deoxy” refers to a “missing” hydroxyl group on the 2-carbon, which has an H instead). The attached nitrogenous base can be a purine, which is a 6-member ring fused to a 5-member ring, or a pyrimidine, which is a single 6-membered ring.
    • 2.6: Amino Acids
      Most of the major molecules of the cell - whether structural, like cellular equivalents of a building’s girders and beams, or mechanical, like enzymes that take apart or put together other molecules, are proteins. Proteins interact with a wide variety of other molecules, though any given interaction is usually quite specific. The specificity is determined in part by electrical attraction between the molecules.
    • 2.7: Fatty Acids
      Unlike monosaccharides, nucleotides, and amino acids, fatty acids are not monomers that are linked together to form much larger molecules. Although fatty acids can be linked together, for example, into triacylglycerols or phospholipids, they are not linked directly to one another, and generally no more than three in a given molecule. The fatty acids themselves are long chains of carbon atoms topped off with a carboxyl group. The length of the chain vary, but most are between 14 and 20 carbons.