R1.1: Normal Cell Structure

There are two major compartments in the cell:

  • The cytoplasm contains the structures of the cell outside of the nucleus. The cell membrane forms the boundary of the cytoplasm and the cell.
  • The nucleus is the central, darker staining part of the cell which contains the chromosomes.


The cytoplasm contains numerous organelles which perform cellular functions:

  • Mitochondria are energy producing organelles with their own mitochondrial DNA.
  • Endoplasmic reticulum is involved in the assembly of proteins. Rough endoplasmic reticulum contains ribosomes which translate messenger RNA into protein.
  • The golgi apparatus is involved in the packaging of protein into membrane bound organelles, either for storage or for delivery to the cell membrane
  • Centrioles are small assemblies of microtubles arranged in a cylinder. They are important localisation of the chromosomes during cell division.

The cytoskeleton extends through the cytoplasm, attached to cell membrane proteins. The cytoskeleton helps to cell to keep its shape and is also mobile in some cells (such as neutrophils), altering the shape of the cell and allowing movement. Tumour cells frequently co-opt the cytoskeleton to allow them to move through tissues.



The nucleus contains the DNA, stored in 44 somatic and two sex chromosomes. The nucleus may also contain a nucleolus, a site of ribosome manufacturing. The double-membrane of the nucleus contains numerous pores which allow proteins and RNA to communicate with the cytoplasm.