Summary
Summary PROKARYOTIC CELLS AND THE ENDOSYMBIOTIC THEORY
- Module
- Unit 2 - Cells
- Institution
- AQA
Notes on PROKARYOTIC CELLS AND THE ENDOSYMBIOTIC THEORY
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BY JHENICA UTHAYAKUMARANPROKARYOTIC CELLS
Prokaryotic cells are smaller than eukaryotic cells and have no nucleus or nuclear envelope. Even though they may lack some membrane-bound organelles,
prokaryotic cells share some of the same features as eukaryotic cells:
1) The plasma/cell membrane= this acts as a physical barrier which controls what enters and leaves the cell. Furthermore, it enables the cell to communicate
with its neighbours and surroundings.
2) The ribosomes = even though the ribosomes are smaller than those in eukaryotic cells they are still able to undergo protein synthesis as they are made of
protein and ribosomal RNA. They are involved in the process of translation, in which proteins are synthesised from messenger RNA.
3) Cytoplasm = the cytoplasm holds all the chemicals of the cell and is where chemical reactions take place. It contains water, proteins, and organic and
inorganic molecules.
4) Cell wall (present in some eukaryotic cells; plants cells etc.) = In prokaryotic cells, the cell wall is usually made up of peptidoglycan (murein). In bacteria,
the cell wall may also contain other proteins, depending on whether they are Gram-positive or Gram-negative. In both eukaryotic cells and prokaryotic
cells the cell wall provides strength and rigidity to the cell structure and is permeable to allow diffusion of solutes.
Other features of prokaryotic cells:
1) (Slime)Capsule = This outmost layer in a prokaryotic cell is made of thick polysaccharide, making it highly organised and not easily removed.
2) Circular DNA= These contain the genomic DNA of the cell.
3) Nucleoid region= The region of the cytoplasm that contains the circular DNA.
4) Flagella = Long, ‘whip-like’, rigid tails that rotate to help the cell move in its surroundings.
5) Pili = These can ‘fix’ the cell to a surface and can aid the exchange of genetic information between cells.
ENDOSYMBIOSIS
A type of symbiosis in which one symbiotic organism lives inside another.
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