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