Organic Macromolecules

Brief Revision of Chemistry


  • The building block of matter
  • There are more than 100 different types of atoms known, as shown in the Periodic Table. Only 92 are naturally-occurring with hydrogen as the lightest and uranium as the heaviest of these.
  • The most common atoms on earth are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P) and sulphur (S).






Base or Alkali

Organic Macromolecules




Lipids (Fats & Oils)


  1. Long-term energy storage, providing 6 times as much energy as carbohydrates
  2. Lipids and proteins are the major structural components of cell membranes
  3. Insulation e.g. whale blubber


Proteins (Polypeptides)

  1. Supporting structure (e.g. cell membranes)
  2. Metabolism (e.g. enzymes)
  3. Immune defence (e.g. antibodies)
  4. Body regulation (e.g. hormones)
  5. Last resort energy source after carbohydrates and lipids
  1. Fibrous Proteins - structural proteins that resemble coiled springs (e.g. keratin in hair, collagen in skin, myosin in muscle)
  2. Globular Proteins - functional proteins that have irregular shapes (e.g. enzymes, hormones, antibodies)
  3. Conjugated Proteins - composed of both protein and non-protein parts (e.g. lipoproteins in cell membranes, nucleoproteins in the cell nucleus)

Nucleic Acids (DNA and RNA)

2 Types of Nucleic Acids

  1. DNA or Deoxyribonucleic Acid forms the genes, and is found only in the nucleus of cells
  2. RNA or Ribonucleic Acid is found in the nucleus, ribosomes, and some other parts of the cell such as mitochondria and chloroplasts


  1. a nitrogen-containing base (adenine, guanine, cytosine, thymine or uracil)
  2. a phosphate group
  3. a sugar (ribose or deoxyribose)

Complementary Nitrogen Bases

  1. Purines (adenine and guanine)
  2. Pyrimidines (cytosine, and thymine or uracil)

Structure of DNA

Structure of RNA

  1. Messenger RNA (mRNA)
  2. Transfer RNA (tRNA)
  3. Ribosomal RNA (rRNA)