• The key molecules that are required to build structures that enable organisms to function are:
  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids
  • Water

The key biological molecules for living organisms

• Carbohydrates, proteins, lipids and nucleic acids contain the elements?carbon?(C) and?hydrogen?(H) making them?organic compounds
• Carbon atoms are key to the organic compounds because:
  • Each carbon atom can form?four?covalent bonds?– this makes the compounds very stable (as 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?(monomers)?that bond with many repeating subunits to form large molecules?(polymers)?by a process called?polymerisation
• Macromolecules?are very large molecules
  • That contain 1000 or more atoms therefore having a?high molecular mass
  • Polymers can be macromolecules, however?not?all?macromolecules are polymers as the subunits of polymers have to be the?same?repeating units

Carbohydrates

• Carbohydrates are one of the main carbon-based compounds in living organisms
• All molecules in this group contain?C,?H?and?O
• As?H?and?O?atoms are always present in the?ratio?of?2:1?(eg. water H2O, which is where ‘hydrate’ comes from) they can be represented by the formula?Cx?(H2O)y
• The three types of carbohydrates are?monosaccharides,?disaccharides?and?polysaccharides

Types of carbohydrate table

• The most well-known carbohydrate?monomer?is?glucose
• Glucose has the molecular formula?C6H12O6
• Glucose is the most common?monosaccharide?and is of central importance to most forms of life
• There are different types of monosaccharide formed from molecules with varying numbers of carbon atom, for example:
  • Trioses (3C) eg. glyceraldehyde
  • Pentoses (5C) eg. ribose
  • Hexoses (6C) eg. glucose
• Glucose exists in two structurally different forms –?alpha (α)?glucose and?beta?(β) glucose?and is therefore known as an?isomer
  • This structural variety results in different functions between carbohydrates

Straight chain and ring structural formula of alpha & beta glucose

• Different?polysaccharides?are formed from the two isomers of glucose

Structure of polysaccharides table