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1、Specification Learning Objective: Structural differences between bacteria and viruses and their role in health and diseasePresentation: Screen 1 In 1994 there was widespread reporting by the media of a flesh eating bug in the UK. This superbug was destroying human flesh at the rate of one inch per h
2、our. The media hype led to widespread public anxiety. The condition necrotising fasciitis is caused by Streptococcus pyogenes, and is a very rare complication of surgery or other debilitating conditions. In many instances during the reporting of this case, the microbe responsible was wrongly reporte
3、d to be a virus. Bacteriophages a particular type of virus were also implicated. It was suggested that bacteriophages were altering the genetic makeup of the bacteria making it more virulent and resistant to antibiotics therefore leading to an epidemic of the condition. A basic understanding of the
4、differences between bacteria and viruses would have alleviated the concerns of the public since much of what was reported was at best misleading and at worst blatantly wrong. Screen 2 In order to understand the influence of bacteria and viruses on health and disease we need to compare their differen
5、t structures. You may already know some of the structural characteristics of bacteria and viruses if you dont dont worry you are going to learn about their structures by a process of trial and test. You will be presented with a list of structural components with descriptions of their characteristics
6、 and function. First of all familiarise yourself with these by clicking on each and reading through their descriptions.1.Size/scale 2.Capsid 3.Spike proteins 4.Helical/Icosahedral Shape 5.DNA strand 6.RNA strand 7.Chromosomes 8.Outer membrane 9.Plasmids 10. Ribosomes 11. Flagellum 12. Pili 13. Endos
7、pores 14. Cell wall 15. capsule 16. prokaryote1. Size scale (student should drag the correct size into the box)Bacteria are microorganisms that are between 0.5 and 5 m (micrometer) in diameter. If you took a metre rule and divided it into a million sections (106) each section would represent 1 micro
8、meter or m a large bacterium of 5 m would sit across 5 of these micrometer sections that gives you an indication of how small they are. Viruses are even smaller than that they are about 20-200 nm (nanometres) in diameter. In this case you would have to divide your metre rule into a thousand million
9、(109)sections and each section would represent a Screen 1 Can we use some images of countryside to pretend we are in GloucestershireMock up od newspaper headlines (dont suppose we can use real ones).Flash up images of bacteria and viruses and a bacteriophage as these words appear in the text.Screen
10、2 Images etc:http:/en.wikipedia.org/wiki/Virus Some illustrations also at will need to redraw these breaking them down into the different structural components http:/w3.dwm.ks.edu.tw/bio/activelear ner/23/ch23summary.htmlhttp:/www.hillstrath.on.ca/moffatt/bio3 a/microbio/bactvir.htmlList of structur
11、al components of bacteria and viruses randomly arranged. When student clicks they get a picture of the component and a brief description of what it is and its role in the bacteria and virus (without giving away which it is found within)1. Bacteria 0.5 - 5 m in diameterVirus 20 - 200 nm Add an analog
12、y to show the relative sizes ie size of the moon vs tennis ball?Or use the metre rule and zoom in nanometre. The largest virus would cover about 200 of these nanometre sections. 2. Capsid (Developer note: this should be dragged into the virus box it sticks if it is in the right box but it bounces ba
13、ck if put into the bacteria box with the feedback “No this structure does not belong to bacteria try again”)A protective shell made from protein molecules. The capsid protects the components within it from being broken down by enzymes produced by the target cells. Sometimes the capsid plays a part i
14、n the attachment of the microorganism to the target cell.3. Spike proteins (Developer note: this should be dragged into the virus box it sticks if it is in the right box but it bounces back if put into the bacteria box with the feedback “No this structure does not belong to bacteria try again”)These
15、 arent always present but do play a very important role. They recognise and bind to specific structures on the surface of target cells ensuring it is attaching to the right host. It can also work the other way the host cell might produce antibodies against the spike proteins to prevent attachment an
16、 immune response from the immune system.4. Helical/Icosahedral shape (Developer note: the helical or isohedral shape should be dragged into the virus box it sticks if it is in the right box but it bounces back if put into the bacteria box with the feedback “No this structure does not belong to bacteria try again”). Capsid coats can be helical or icosahedral in shape. An isohedron is a 3 dim
