Internal membranes subdivide the eukaryotic cell into different functional compartments which are absent in prokaryotic cells. The development of compartmentalisation in eukaryotic cells was advantageous through its effects on cell volume, energy capture and gene expression regulation. However, problems arose from these advantageous adaptions and centre around issues such as substance transport and distribution, rate of macromolecular turnover, diffusion across membranes and the slowed rate of cell replication. This essay will discuss how these problems were overcome by further developments of the eukaryotic cell.
Compartmentalization allows for the eukaryotic cell to maintain a large volume. Certain advantages are enabled through this, for example: cells are able to function as larger muscle cells. However, the surface area to volume ratio is affected negatively as there is not enough surface area on the plasma membrane of the cell to accommodate the amount of metabolic activity required for efficient functioning. The organelles involved in the compartmentalisation of the cell contribute to the alleviation of this problem by developing their own plasma membranes, providing sufficient surface area for various chemical processes to be carried out. Required transport of the resultants of these metabolic processes is resolved by the presence of the cytoskeleton. Not only is the cytoskeleton responsible for the mechanical support and shape maintenance of the cell, but it is highly involved in cell motility. Tubulin-dimers – microtubules - form a track which guides secretory vesicles from the Golgi apparatus to the plasma membrane using motor proteins – dynein and kinetin. Actin filaments – microfilaments - are responsible for contraction within muscle cells making use of the protein, myosin. Cell streaming within plants, which brought about through these actin-myosin interactions, speeds the distribution of materials within the cell.
