Monosaccharides

  • Monosaccharides are the monomers of Carbohydrates. Carbohydrates make up about 1/10 of the organic matter in a cell, their functions include:
    • Energy Sourceage - They provide the enegry for respiration
    • Energy Storage - They store energy
    • Structure - For example Cellulose
  • They contain the elements Carbon, Hydrogen and Oxygen in the proportions \(C_n(H_2O)_n\).

  • Monosaccharides come in many different forms, ranging from three to six carbon atoms. They all: are soluble in water, are sweet tasting and form crystals. They are grouped according to the number of Carbon atoms, being called triose, tetrose, pentose or hexose sugars, the most common being hexose sugars. Pentose and hexose sugars tend to form ring structures.

  • When Glucose forms a ring structure, it can do so in two different ways. If the \(OH\) at \(C_1\) is below the plane of the ring, it is called an α Glucose, if the \(OH\) at \(C_1\) is above the plane of the ring, it is called β Glucose. This difference in structure leads to a difference in properties.

β and α forms of glucose. Note how in the β form the OH is above, while in the α form it is below
β and α forms of glucose. Note how in the β form the \(OH\) is above, while in the α form it is below
  • Monosaccharides can be bonded together (for example, to produce a disaccharide, or maybe even a polysaccharide, like Starch) with a Condensation Reaction, forming a Glycosidic Bond. This bond can be broken by Hydrolysis. The bond is named after the Carbon atoms that are involved in the bond, for example, the bond between two Glucose molecules in Amylose is called a (1→4) Glycosidic Bond, as the bond is between \(C_1\) of one monomer and \(C_4\) of another.

Written by Sam Adam-Day.