Chapter 23: Viruses Leaving Certificate Biology Higher Level.
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Transcript of Chapter 23: Viruses Leaving Certificate Biology Higher Level.
![Page 1: Chapter 23: Viruses Leaving Certificate Biology Higher Level.](https://reader036.fdocuments.net/reader036/viewer/2022082613/5697bf7d1a28abf838c84621/html5/thumbnails/1.jpg)
Chapter 23: VirusesChapter 23: Viruses
Leaving Certificate BiologyLeaving Certificate Biology
Higher LevelHigher Level
![Page 2: Chapter 23: Viruses Leaving Certificate Biology Higher Level.](https://reader036.fdocuments.net/reader036/viewer/2022082613/5697bf7d1a28abf838c84621/html5/thumbnails/2.jpg)
VirusesViruses• Viruses are obligate parasites – they can
only reproduce inside a living host• Viruses are non-cellular: made of a piece of
DNA oror RNA surrounded by a protein coat• Syllabus: “Viruses: identify the problem of
definition”– The problem of definition comes from the debate
as to whether or not viruses are living or non-living
– Viruses do not show all the characteristics of living things: organisation; nutrition; excretion; response; reproduction
![Page 3: Chapter 23: Viruses Leaving Certificate Biology Higher Level.](https://reader036.fdocuments.net/reader036/viewer/2022082613/5697bf7d1a28abf838c84621/html5/thumbnails/3.jpg)
Virus ShapesVirus Shapes
• Round/spherical-shaped
• Rod-shaped
• Complex-shaped
![Page 4: Chapter 23: Viruses Leaving Certificate Biology Higher Level.](https://reader036.fdocuments.net/reader036/viewer/2022082613/5697bf7d1a28abf838c84621/html5/thumbnails/4.jpg)
Virus StructureVirus Structure
• Viruses are composed of a single piece of either DNA or RNA surrounded by a protein coat
Protein coat
Piece of DNA or RNA
![Page 5: Chapter 23: Viruses Leaving Certificate Biology Higher Level.](https://reader036.fdocuments.net/reader036/viewer/2022082613/5697bf7d1a28abf838c84621/html5/thumbnails/5.jpg)
Viral ReplicationViral Replication1. Attachment: virus attaches to proteins on the target cell’s
surface2. Entry: either the whole virus enters the cell by pushing into
the cell or the virus injects its DNA/RNA into the host cell3. Synthesis of viral DNA and viral proteins: the virus
causes the cell’s own DNA to become inactive and uses the cells ribosomes and organelles to make new DNA/RNA and protein
4. Assembly of new viruses: the newly synthesised DNA/RNA and viral proteins assemble themselves into new viruses
5. Release of new viruses: the number of new viruses build up in the host cell until the host cell bursts and releases all the newly-formed viruses which go on to infect other cells
![Page 6: Chapter 23: Viruses Leaving Certificate Biology Higher Level.](https://reader036.fdocuments.net/reader036/viewer/2022082613/5697bf7d1a28abf838c84621/html5/thumbnails/6.jpg)
Economic and Medical Economic and Medical Importance of VirusesImportance of Viruses
• Two harmful effects of viruses:– AIDS (acquired immunodeficiency syndrome) caused
by the HIV (human immunodeficiency virus) – which is a retrovirus (contains RNA)
– Human papilloma virus: causes cervical cancer by integrating its own DNA into the host cells DNA and remains dormant
• Beneficial effect of viruses:– Used in genetic engineering to transfer genes
especially between bacteria– It is possible that bacteriophages might be used to kill
bacterial infections in the future