Summary of the differences between Prokaryotic and Eukaryotic Cells.
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Examples of prokaryotic cells are:
- Bacillus Bacteria
- E. coli Bacteria
- Salmonella Bacteria
Examples of Eukaryotic cells are:
- Red blood cells
- Centric Diatom
- Golden Colonia Alga
Eukaryotic cell:
Prokaryotic cell:
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2. What is endosymbiosis and how does it explain the existence of mitochondria and chloroplasts?
An endosymbiont is any that lives within the body or cells of another organism, i.e. forming an endosymbiosis. Examples are (called ) which live in on roots, single-celled inside reef-building , and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects.
Endosymbiosis is the process by which prokaryotes gave rise to the first eukaryotic cells. Chloroplasts in plants and mitochondria in other eukaryotes are thought to have evolved through a form of endosymbiosis.
One theory is that the mitochondria evolved from small hetrotrophic prokaryotes that were engulfed by a larger eukaryotic cell. Another theory is that mitochondria and chloroplasts are the result of years of evolution initiated by the endocytosis of bacteria and blue-green algae which became symbiotic instead of digested.
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It is thought that cell organelles such as nuclei, chloroplasts and mitochondria are developed from prokaryotic cells that became incorporated inside larger prokaryotic cells. This is backed up by the following observations:
- Organelles contain circular DNA.
- They contain 70S ribosomes.
- Organelles have a bilayer membrane, as if a single-membrane had been engulfed and surrounded by another.
- Organelles reproduce by binary fission.
- Organelles are very like some bacteria that are around now.
3. What is phagocytosis?
Phagocytosis is the cellular process of engulfing solid particles by the cell membrane which forms an internal phagosome. When the phagocytic white cell detects bacteria, it moves its cytoplasm and cell wall towards the bacteria. The extensions of the cell that form during this movement are called pseudopodia, false feet.
The cell membrane of the white cell completely surrounds a bacterium, enclosing it in a self contained vesicle called a phagosome. This vesicle is inside the white cell but the bacterium is a prisoner, surrounded by an internal cell wall to keep it away from the cell's cytoplasm.
An organelle called lysosome is involved in the breakdown of the cellular components, which then fuses with the phagosome. The contents are degraded and either released intracellulary to undergo further processing or extracellulary via exocytosis.
Phagocytic cells are either one-celled organisms or one of the body cells, such as a . Bacteria, dead tissue cells and dust particles are all examples of particles that may be phagocytosed. Example, a white blood cells are of the defending the body against both and foreign materials. They engulf potentially harmful or foreign objects in the blood therefore protecting the body from attack.
A diagram of the process of phagocytosis is shown below.
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