What is a Cell
What is a Cell?
"The basic structural and functional unit of living organism; the smallest structure capable of performing the essential functions characteristic of life"
A Prokaryote is a catagory of organisms characterised by absence of a true nucleus and other membrane bound organells.
Prokaryote's are simple cells
Prokaryote's include both groups, Bacteria and Archea
Eukaryotes are a catagory of organisms whose cells are characterised by the presence of a membrane bound nucleus and other membrane bound organelles.
Eukaryotes are complex, compartmentalised cells.
Examples of Eukaryotes include:
An organelle is: Any membrane bound intracellular structure that is specialised for carrying out a particular function.
An Organelle allows eukaryotic cells to be bigger then prokaryotic cells, and carry out more complex functions.
Some Organelle's are Ubiquitous
Some are only found in particular cell types.
Nucleus - Organises Genetic Material
Mitochondria - Makes Cellular Energy
Chloroplasts - Carry out Photosynthesis
Lysomes - Break down material not wanted by the cell
Mitochondria and Chloroplasts are thought to have derived from symbiotic bacteria.
This means that both Mitochondria and Chloroplasts at one point, were in their own right bacteria and they migrated into other cells, forming a symbiotic relationship.
Evidence for Symbiotic Theory
Both Prokaryotes and the two organelles (Mitochondria and Chloroplast) have plasmid DNA contained within them, not only this but the DNA is very similer.
The Genes found within the DNA is very similer.
Several antibodies have the same effect on both Mitochondria and Chloroplast
Both Mitochondria and Chloroplast have a double membrane.
- Occurs in certain sea slugs and mollasks
- Animals incorporates chloroplasts from the green algae it eats into its cells
- Chloroplasts provide carbohydrates for the animal.
- This in effect, alows the animal to photosynthesis, using the chloroplast from it's food source.
- Viruses aren't a cell as they can not independantly survive and replicate
- Viruses highjack a living cells machinery to replicate
- Microbiologists usually include them as a type of microbe though
A microbe is classed as any microscopic organism (Microscopic being anything you cannot see with the naked eye)
There is a very wide variety of types and sizes and they can be found in all habitats
Microbes can be eaither unicellular or multicellular
Examples of Microbes include:
Prokaryotic Organelles and Magnetosomes
Although Prokaryotes are described as not having organelles in recent years we have began to found organelle like structures within some bacteria.
Although there is no official way of classifying these potential organelles as of yet, for now they are described as being organelle like structures, as once they become classed as organelles, this would cause the deffinition of Prokaryotic to be incorrect.
An example of this issue is shown in Magnetotactic bacteria.
Magnetotactic Bacteria can sense the presence and direction of magnetic fields and align themselves with them. They do this using Magnetosomes, which could be classed as Organells how ever due to them being found in Prokaryotes, classifiying them it still something that needs to be done. For now they are "Organelle Like Structures".