Eukaryotic cells are large and have a nucleus bounded by nuclear membranes, also known as the nuclear envelope
Prokaryotic cells are smaller and have no nucleus or nuclear envelope
Bacteria are versatile, adaptable and successful as a result of their small size, ranging from 0.1 to 10 micrometres in length
All bacteria possess a cell wall, which is made up of murein, which is a polysaccharide with peptide bonds. Many bacteria protect themselves with a capsule of mucilaginous slime around this wall
Inside the bacterial cell wall, there is a cell-surface membrane, within which is the cytoplasm that contains 70S ribosomes. These ribosomes are smaller than those found in eukaryotic cells but these still synthesise proteins
Bacteria store food reserves as glycogen granules and oil droplets. The genetic material in bacteria is in the form of a circular strand of DNA
Plasmids reproduce themselves independently and give the bacterium resistance to harmful chemicals such as antibiotics. They are also used as carriers of genetic material in genetic engineering
Another name given to murein is peptidoglycan
Bacteria do not have chloroplasts, only bacterial chlorophyll associated with the cell-surface membrane in some bacteria
Viruses are acellular, non-living particles. They are smaller than bacteria ranging from 20-300nm
They contain nucleic acids such as DNA and RNA as genetic material but can only multiply inside living host cells. The nucleic acid is enclosed within a protein coat called the capsid
Some viruses, like HIV are further surrounded by a lipid envelope. The lipid envelope or capsid have attachment proteins which are essential to allow the virus to identify and attach to the host cell
HIV: Human immunodeficiency virus, a virus that attacks the immune system and causes AIDS
Flagellum is used for locomotion. Some species contain multiple, some have none
Reverse transcriptase is an enzyme that catalyzes the conversion of RNA to DNA. Viruses do this toreplicate their genome
Attachment proteins can be viewed as the key that opens the cellular door to allow the virus to enter the cell