MadSci Network: Cell Biology
Query:

Re: how the different organelles of the egg cell work 2gether to make the cell.

Date: Thu Oct 11 19:58:21 2007
Posted By: Mike Klymkowsky, Professor
Area of science: Cell Biology
ID: 1191043412.Cb
Message:

Organelles


Your question, "how the different organelles of the egg cell work together to make the cell" is a little confusing for me.

Perhaps the most important point to recognize is the continuity of cells, cells are made by other cells, not their organelles. This Cell Theory of Life states that once the first cells first formed, sometime around 3.5 to 3.8 billion years ago, subsequent cells have always been the product of other cells.

This implies that there is an unbroken line of descent from modern cells to those first cells.

If we talk about how different organelles work together, that is a different question all together.

In the context of the prokaryotes, i.e. the archea and the eubacteria, both have a relatively simple overall cellular structure, characterized by a cell wall, plasma membrane, and cytoplasm - which contains the cell's genetic material, its chromosome.

In the context of eukaryotes (organisms with cell structure like ourselves), a number of distinct organelles have been recognized: these include the nucleus (which contains the chromosomes), the internal membrane systems, which includes the nuclear envelope, the endoplasmic reticulum, and the Golgi apparatus, and associated with these major membrane systems are the various types of vesicles associated with endo- and exocytosis.

Other organelles are derived from the endomembrane systems. This include lysosomes and peroxisomes.

Finally, there are the mitochondria (in all eukaryotes) and the chloroplasts (found in plants).

These organelles appear to have been derived from originally free-living bacteria symbionts, sometime around 1.5 to 2 billion years ago.

The various "parts" of the cell are involved in different functions, for example genes are transcribed into RNAs in the nucleus, transported through the nuclear envelope, and most function in the cytoplasm.

The activities of the various organelles are coordinated by various "feed-back" mechanisms that lead to stability, and where appropriate, growth, cell division, morphogenesis, and differentiation, to produce the adult (multicellular) organism.

The molecular details of these processes would take much longer to explain.


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