Transmition Electron Microscope (TEM) image of Eukaryotic Cell
Scanning Electron Microscope (SEM) image of Prokaryotic Cell
However there are many more differences/defining features between the two, as you can see from the table below, there are many organelles absent and present in both which helps to show the difference between the two.
The table illustrates quite clearly the difference between the two cell types, and the differences between animal and plant cells. From the table we can also see that not only do prokaryotes have no membrane-bound organelles, but they are also much simpler, with far fewer organelles. However looking at the cell size we can see that prokaryotic cells are easily 10 to 100 times smaller than eukaryotic cell, which can perhaps explain why they are so simple in comparison to the eukaryotic cells.
All eukaryotic cells have within them a functionally interrelated membrane system, the endomembrane system consisting of the nuclear envelope, ER and Golgi apparatus, vesicles and other organelles derived from them, and the plasma membrane.
Many materials are moved around the cell by the endomembrane system, including some proteins.
The common features of prokaryotic and eukaryotic cells are:
1. DNA, the genetic material contained in one or more chromosomes and located in a non membrane bound nucleus in prokaryotes and a membrane-bound nucleus in eukaryotes
2. Plasma membrane, a phospholipids bi-layer with proteins that separates the cell from the surrounding environment and functions as a selective barrier for the import and export of materials
3. Cytoplasm, the rest of the material of the cell within the plasma membrane, excluding the nucleus, that consists of a fluid portion called the cytosol, the organelles and other particulates suspended in it.
4. Ribosome’s, the organelles on which protein synthesis takes place
Endosymbiosis
As I have mentioned in the first paragraph: Prokaryotic cells are far older and more diverse than eukaryotic cells. Prokaryotic cells have probably been around for 3.5 billion years, while eukaryotic cells arose only about 1 billion years ago. It is thought that eukaryotic cell organelles like nuclei, mitochondria and chloroplasts are derived from prokaryotic cells that became incorporated inside larger prokaryotic cells. This idea is called endosymbiosis, and is supported by these observations:
- Organelles contain circular DNA, like bacteria cells.
- Contain 70S ribosome’s, like bacteria cells.
- Organelles have double membranes, as though a single-membrane cell had been engulfed and surrounded by a larger cell.
- Organelles reproduce by binary fission, like bacteria.
- Organelles are very like some bacteria that are alive today.
by
ikraziiex3 (student)
