Prokaryotic cells
Introduction

Topic 1 Cell theory

Topic 2 Prokaryotic cells

Topic 3 Eukaryotic cells

Topic 4 Cell Division

Topic 5 Cell membranes


What are prokaryotic cells?

There are two types of cells found in living organism which are prokaryotic and eukaryotic cells. Prokaryotic have no definate nucleus. The DNA can lie free in the cytoplasm in a ring form but not enclosed with a nuclear membrane. An example of a prokaryotic cell is a bacteria or cyanotacteria. Bacterias are the smallest living organisms with a cellurar structure. They are single cells but some are joined together( bluegreen bacteria).

  This is a picture of a bacteria done in a computer.

Structures of Prokayotic cells:

Cell wall: it is strong an rigid. The cell wall prevents the cell from bursting when it absorves water by osmosis. The cell wall is made out of Nurenin, a molecule that consists of a parallel polysaccharide chain cross-linked at regular intervals by short chain of aminoacis.

Plasma membrane: it is made out of phospholipids. It controls the exchange of waste materials and nutrients. It is fully permeable. The membrane can also be used as a receptor of hormonmes and neurotransmiters and other chemicals.

Mesosomes: they are infoldings of the surface cell divisions. They organise the separation of two daughter cell and help in the formation also of cross wall between doughter cell.

Ribosomes: They are tiny organelles ( 70s ). They are found in large number in the cytoplasm. Each ribosome consists of 2 subunit. Ribosmes are made up of equall amounts of RNA and proteins. The RNA is made in the nucleus. They are the sites of protein synthesis.

Naked DNA: Unit of unheritance ( genetic material ) organised usually into genes andchromosomes but lies freely in the cytoplasm of prokaryotic cells.

 

Metabolic activity of rpokaryotic cells:

Photosynthesis: CO2 + H2O = glucose ( C6H12O6 ) + O2

Fermentation: the breaking down of glucose

glucose = ethanol + energry

Nitrogen fixation: bacteria can live freely in the soil or live in the roots. This bacteria uses nitrogen in the air and changes it into nitrates so the plant can make aminoacids and proteins. In exchange the plant feeds the bacteria.

  This is a picture of a Phylum Proteobacteria which is involved in the nitrogen fixation process.