Half - term Test: Revision

There are two basic types of cells:

• Prokaryotic - bateria and cyanobacteria ( which used to be called blue-green algae)
• Eukaryotic - all other cells, such as protoctista, fungi, plant and animal cells. 

Prokaryotic Cells

• Size: 0.5 - 5 µm
• Cells Wall: Yes - contains pepitdoglycan
• Genetic Materials: DNA is naked, a single circular molecule
• Ribosome:  70S ribosomes (smaller)
• ER: None
• Golgi Apparatus: None
• Mitochondria: No - respiration occurs on an in folding of the cell membrane mesosome 

Eukarytoic Cells 

• Size: 
• Cell Wall: Yes (plant) / No (animals)
• Genetic Materials: DNA linear, associated with histones (proteins), in a nucleus, surrounding by a nuclear envelope.
• ER: Yes
• Golgi Apparatus: YEs
• Mitchondria: Yes 

Endoplasmic Reticulum are: 

• A system of flattened cavities lined by a thin membrane (cisternae) 

• It is the site of the synthesis of many substances in the cell and so provides a compartmentalised area.

• The cavities are also a transport system whereby substances move through them from one part of the cell to another. 

There are two different types of endoplasmic reticulum

- rough endoplasmic reticulum (rough er) 

- smooth endoplasmic reticulum (smooth er) 

• Have ribosomes (which are made up of RNA & protein) attached to the cytosolic side of their membrane
• Found in cells that are making proteins for export (enzymes, hormones, structural proteins, antibodies)
• Thus, involved in protein synthesise
• Modifies proteins by the addition of carbohydrates, removal of signal sequences
• Phospholipid synthesis and assembly of polypeptides

• Have no ribsomes atatched and often appear more tubular than the rough ER
• Necessary for steroids synthesis, metabloilsm and detoxification and lipid synthesis 
• Numerous in the liver