monosaccharides

Monosaccharides: Structure

• Carbohydrates are one of the main carbon-based compounds in living organisms

• All molecules in this group contain C, H and O

  • Carbon atoms are key to the structure of organic compounds because

    • Each carbon atom can form covalent bonds; this makes the compounds very stable

      • Covalent bonds are so strong they require a large input of energy to break them

    • Carbon atoms can form covalent bonds with oxygen, nitrogen and sulfur

    • Carbon atoms can bond to form straight chains, branched chains, or rings

• Carbon compounds can form small, single subunits, or monomers, that bond with many repeating subunits to form large molecules, or polymers

  • This is a process called polymerisation

• The three types of carbohydrates are monosaccharides, disaccharides, and polysaccharides

Monosaccharides

• Monosaccharides are the monomers of carbohydrate; they can join together to make carbohydrate polymers

  • Monosaccharides are simple carbohydrates

  • Monosaccharides are sugars

• There are different types of monosaccharide formed from molecules with varying numbers of carbon (C) atoms, for example

  • Triose (3C) eg. glyceraldehyde

  • Pentose (5C) eg. ribose

  • Hexose (6C) eg. glucose

• Glucose is a well known example of a monosaccharide

  • Glucose is a hexose sugar

  • The six carbons that make up glucose form a ring structure

    • Carbons 1-5 form a ring, while carbon 6 sticks out above the ring

• Glucose comes in two forms; alpha () and beta ()

  • The forms of glucose are almost identical; they differ only in the location of the H and OH groups attached to carbon 1

    • Alpha glucose has the H above carbon 1 and the OH group below

      • Remember = alpha has the H above

    • Beta glucose has the H below carbon 1 and the OH group above

      • Remember = beta has the H below

Alpha glucose (top) has the hydrogen above carbon 1 and the OH group below, while beta glucose (bottom) has the hydrogen below carbon 1 and the OH group above

Monosaccharides: Function

• The main function of monosaccharides is to store energy within their bonds

  • When the bonds are broken during respiration, energy is released

• The structure of glucose is related to its function as the main energy store for animals and plants 

  • It is soluble so can be transported easily

  • It has many covalent bonds which store energy

• Monosaccharides can combine through condensation reactions to form larger carbohydrates

• Some monosaccharides are used to form long, structural fibers, which can be used as cellular support in some cell types