Biological Molecules

Biological Molecules: The Basics

  • Biological molecules are a group of substances that are vital for life and are found in living organisms.
  • They form the structure of a cell and carry out many of its functions, and can be grouped into four major categories: carbohydrates, proteins, lipids, and nucleic acids.
  • All biological molecules contain elements such as carbon, hydrogen, oxygen, nitrogen, and sometimes sulphur and phosphorus.

Carbohydrates

  • Carbohydrates are energy storage and transport molecules. They include sugars, starch and cellulose.
  • They are made up of elements carbon (C), hydrogen (H) and oxygen (O) with typically a ratio of H:O being 2:1 (like water).
  • Examples of simple carbohydrates (or monosaccharides) include glucose and fructose.
  • Disaccharides, such as sucrose or lactose, are formed by the condensation of two monosaccharides.
  • Polysaccharides are complex carbohydrates formed by combining hundreds or thousands of monosaccharides. Examples include starch (storage polysaccharide in plants) and cellulose (structural polysaccharide in plants).

Proteins

  • Proteins are macromolecules that serve many functions in organisms including catalyzing metabolic reactions, replicating DNA, responding to stimuli, and transporting molecules.
  • Proteins are made up of one or more chains of amino acids, which are linked together by peptide bonds in a specific order as determined by genes.
  • The structure of a protein is critical to its functioning and it can have four levels of structure: primary, secondary, tertiary, and quaternary.

Lipids

  • Lipids are a diverse group of hydrophobic biological molecules that are insoluble in water but soluble in nonpolar solvents.
  • They include fats, oils, waxes, phospholipids, and steroids.
  • Fats and oils are used for long-term energy storage.
  • Phospholipids are major components of all cell membranes.
  • Steroids function as hormones and play other roles.

Nucleic Acids

  • Nucleic acids, including DNA and RNA, are macromolecules that store and transmit genetic information.
  • DNA, or deoxyribonucleic acid, is the genetic material that carries information about an organism and is passed from parent to offspring.
  • RNA, or ribonucleic acid, translates the code stored in the DNA and allows for the synthesis of proteins.