Prokaryotic Cells Sarah Verghese Revision for End of Chapter test

What it is? Prokaryotic cells are smaller than Eukaryotic cells. Bacteria's are prokaryotic cells.

Features for prokaryotic cells Contains:  The cell wall  The plasma membrane  Flagella  Pili  Ribosomes  The nucleoid (region containing free DNA)

Cell wall Cell wall protects and maintains the shape of the cell Composed of carbohydrate-protein complex called peptidoglycan. Some bacteria has an additional layer called polysaccharide outside the cell.

Plasma Membrane Found inside the cell wall and is similar to the membranes of Eukaryotic cells Controls the movement of materials in and out of the cell. Plays a role in binary fission Cytoplasm occupies the interior part of the cell Most visible structure of the cell with a microscope is the chromosome or a molecule of DNA. No compartmentalization within the cytoplasm because there are no internal membranes other than plasma membrane. All cellular processes happens in the cytoplasm.

Pili and Flagella They’re hair-like growths outside the cell wall. Main function is to join bacterial cells in preparation for transferring of DNA for sexual reproduction Some bacteria have flagella that are longer than pili. Flagella allows the cell to move.

Ribosomes Occurs in all prokaryotic cells Function is to synthesise proteins Occurs in large numbers in cells that produces proteins Give a granular appearance on the electron micrograph.

Nucleoid region It is non-compartmentalized and contains a long continuous thread of DNA Bacteria also contain plasmids DNA molecules are not connected to the main bacterial chromosome. Plasmids replicate independently Plasmid DNA isn’t required by the cell under normal conditions but could help adapt to unusual circumstances. Nucleoid

Binary fission Prokaryotic cells can divide simply by binary fission During the process, DNA cells are copied and the two daughter cells become attached to the different regions on the plasma membrane and then it divides into identical daughter cells. The process contains an elongation of the cell and the partitioning of the new DNA by microtubule- like fibres called FtsZ.

A summary of the major characteristics of prokaryotic cells DNA isn’t enclosed within the membrane and forms one circular chromosome. DNA is free and not attached to proteins Lack of membrane-bound organelles. Ribosomes are complex structures within the plasma membrane and has no exterior membrane. Cell wall is made of peptidoglycan They divide by a simple form of division called binary division. They’re characteristically small in size