Cell Differentiation (DP IB Biology)

Cell Differentiation

• One important process that occurred in the development of the cell was cell compartmentalisation 

• This enabled unicellular organisms to develop specialised functions through specific areas of their cell

  • One example is the nucleus region which contains DNA molecules

  • Another example is the compartmentalisation of energy producing areas formed by the endosymbiosis of mitochondria

• However, even with specialised compartments unicellular organisms have their limitations, and so multicellular organisms evolved 

• In complex multicellular organisms eukaryotic cells become specialised for specific functions

• Specialisation enables the cells in a tissue to function more efficiently as they develop specific adaptations for that role. The development of these distinct specialised cells occurs by differentiation

• These specialised eukaryotic cells have specific adaptations to help them carry out their functions

• For example, the structure of a cell is adapted to help it carry out its function (this is why specialised eukaryotic cells can look very different from each other)

• Structural adaptations include:

  • The shape of the cell

  • The organelles the cell contains (or doesn’t contain)

• For example:

  • Cells that make large amounts of proteins will be adapted for this function by containing many ribosomes (the organelle responsible for protein production)

Example of a specialised cell, a red blood cell

The biconcave shape of red blood cells (erythrocytes) increases the surface area available for oxygen absorption

Gene expression

• Every nucleus within the cells of a multicellular organism contains the same genes, that is, all cells of an organism have an identical genome

• Despite cells having the same genome, they have a diverse range of functions because during differentiation certain genes are expressed ('switched' on)

• Whether a gene is expressed or not is triggered by changes in the environment

• Controlling gene expression is the key to development as the cells differentiate due to the different genes being expressed

• Once certain genes are expressed the specialisation of the cell is usually fixed so the cell cannot adapt to a new function

Expression of genes resulting in cell differentiation