BRAINCAKEProkaryotic Cells
Revision notes for Prokaryotic Cells in Edexcel Biology (8BI0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Bacterial CellBacteria are prokaryotic cells.
- Pili and FlagellaMany bacteria have thin projections from their surface: pili and flagella.
- Cell Surface MembraneLike all cells, a bacterium has a cell surface membrane (plasma membrane).
- PlasmidsA plasmid is a small, circular loop of double-stranded DNA found in the cytoplasm of many bacteria, separate from the main bacterial chromosome in…
- NucleoidProkaryotic cells have no nucleus.
- 70S RibosomesRibosomes are the sites of protein synthesis (translation).
- Gram-StainingGram staining is a differential staining technique that divides bacteria into two groups according to the structure of their cell wall.
- AntibioticsAn antibiotic is a chemical that kills bacteria or stops them growing, without harming the cells of the host.
- Alternative Classification of BacteriaAs well as the Gram stain, bacteria can be classified by their shape and by their respiratory requirements.
- VirusesViruses are tiny infectious particles, usually between about 20 nm and 300 nm across, much smaller than bacteria.
- The Structure of VirusesAll viruses share the same basic plan: a core of nucleic acid protected by a protein coat.
- DNA VirusesViruses are classified mainly by the nucleic acid in their genome.
- RNA VirusesRNA viruses have a genome made of RNA rather than DNA.
- RNA RetrovirusesRetroviruses are a special group of RNA viruses.
- Viral ReproductionA virus has no ribosomes, no enzymes for respiration and no supply of ATP.
- Virus Life CycleAlthough viruses differ in detail, their replication inside a host cell follows the same general sequence of stages: 1.
- DNA Virus LatencyLatency is a state in which a virus is inside a host cell but is not replicating and is not making new virus particles.
- DNA Virus Lytic PathwayIn the lytic pathway, a virus replicates straight after infection and the host cell is destroyed.
- RNA Virus ReplicationRNA viruses face a problem that DNA viruses do not.
- Positive ssRNA VirusesIn positive-sense single-stranded RNA (+ssRNA) viruses, the genome has the same base sequence as mRNA.
- Negative ssRNA VirusesIn negative-sense single-stranded RNA (−ssRNA) viruses, the genome is complementary to mRNA.
- Retrovirus ReplicationRetroviruses such as HIV replicate by copying their RNA genome into DNA and inserting it into the host's DNA.
- Viruses and DiseaseViruses cause disease in several ways, and the symptoms of an infection come from a mix of damage done by the virus and the body's own response.
- The Spread of Viral DiseasesViral diseases spread when virus particles pass from an infected host to a new one.
- Treating Viral DiseasesViral diseases are much harder to treat than bacterial ones.
- Preventing Viral DiseasesBecause viral diseases are hard to treat, prevention is the most effective approach.
- VaccinationA vaccine contains antigens from a pathogen, given so that the body makes an immune response and memory cells without the person having the disease.
- Disease ControlDisease control means the measures a government or health service takes to reduce the spread of an infectious disease through a whole population…
- Drug DevelopmentDeveloping a new drug, such as an antiviral, takes 10 to 15 years and follows a strict series of stages designed to show that the drug is safe and…
- PandemicsDiseases are described by how widely they occur: • Endemic: always present at a steady level in a particular region, e.g. malaria in parts of…
- EthicsMany decisions about treating and controlling viral diseases raise ethical questions: questions about what is right, not just what works.