What is cell biology?

Cells form the basis of all living things. They are the smallest single unit of life, from the simplest bacteria to blue whales and giant redwood trees. Differences in the structure of cells and they way that they carry out their internal mechanisms form the basis of the first major divisions of life, into the three kingdoms of Archaea (“ancient” bacteria), Eubacteria (“modern” bacteria) and Eukaryota (everything else, including us). An understanding of cells is therefore vital in any understanding of life itself.

Cell biology is the study of cells and how they function, from the subcellular processes which keep them functioning, to the way that cells interact with other cells. Whilst molecular biology concentrates largely on the molecules of life (largely the nucleic acids and proteins), cell biology concerns itself with how these molecules are used by the cell to survive, reproduce and carry out normal cell functions.

In biomedical research, cell biology is used to find out more about how cells normally work, and how disturbances in this normal function can result in disease. An understanding of these processes can lead to therapies which work by targeting the abnormal function.

Common cell biology techniques

The following list covers some of the more commonly used cell biology techniques – it is by no means exhaustive.

  • Cell / Tissue Culture – in the same way that bacteria and other simple organisms can be grown in the laboratory outside their normal environment, cells and tissues from more complicated organisms can be cultured as well. The techniques are slightly different, and the culture media are more complex to reflect the complex internal environment inside the host from which the cells are derived, however cell and tissue culture is a powerful tool which provides an almost limitless supply of test material for researchers to use without resorting to using whole organisms. In addition, the controlled conditions in cell and tissue culture allows researchers to carry out experiments with a lower number of variables which may affect the outcome of the test. Cell culture may use cells removed directly from an organism (primary culture), or it may use lines of cultured cancer cells. The benefit of the latter approach is that cancer cells continue to divide, while primary cultures cease dividing after a number of cycles.
  • Microscopy – the basic tool of cell biology is microscopy. Recent advances in imaging technology has allowed an unprecedented amount of information to be gleaned from microscopic analysis. Types of microscopic techniques which are used include :
  • Brightfield – traditional microscopy, where cells are illuminated by visible light. Brightfield microscopy gives a general picture of cell function, although that information is not very detailed or specific. As animal cells lack cell walls, brightfield microscopy may use special techniques such as phase contrast to show cellular structures in more detail. Brightfield microscopy allows imaging of live or fixed (dead) cells and tissues)
  • Electron Microscopy – uses a focused beam of electrons instead of light. Electron microscopy permits a much higher magnification of specimens than light microscopy and is useful in obtaining detailed information about sub-cellular structures. Electron microscopy requires extensive processing and so can only be performed on fixed specimens. Transmission electron microscopy provides a cross section of a specimen, while scanning electron microscopy gives a three-dimensional image of the surface of a specimen.
  • Fluorescence Microscopy – uses fluorescent materials to indicate structures in a specimen. Fluorescence occurs when light of one wavelength “excites” a material and causes it to emit light of a different wavelength. Most fluorescent materials give off visible light after excitation by ultraviolet light. Structures may be naturally fluorescent (autofluorescence) or they may be labeled with a compound which is fluorescent (eg. DAPI is a dye which binds onto DNA. The DNA and nuclei of cells stained with DAPI emit a blue light under ultraviolet light).
  • Immunofluorescence – antibodies are proteins made by the immune system which bind onto specific parts of proteins. Antibodies can be raised against any protein in the cell. If these antibodies are attached to a fluorescent tag, the tag will only show up where that antibody attached (ie. where the target protein is found in the cell). Immunofluorescence allows very specific targeting of cellular structures.
  • RNA Interference – RNA interference uses short sequences of RNA which are complementary to the mRNA which carries to instructions to translate proteins from the DNA to the ribosomes. The interfering RNA binds to the target sequence, preventing it from being translated. As a result, careful selection of interfering RNA can be used to silence a particular gene. This allows researchers to study what role a protein plays in a cell, by observing what happens when that protein is absent.
  • Timelapse Microscopy – many cellular processes (eg. mitosis) occur over a period of time which is not practical for direct observation. Imaging cells over a period of time (eg. a photograph is taken every 20 minutes for 24 hours) allows us to combine these images in a “movie” which compresses a long time period into a shorter one.