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7.4 Protecting the body – Further questions and answers Q1. Bk Ch7 S7.5 FQ1 Prepare a concept map to demonstrate your understanding of the non-specific defence mechanisms involved in defence discussed in this section. Include: skin phagocytes blood vessels cilia neutrophils dead cells other secretions inflammation mucous membranes granuloma white blood cells chemical barriers lymph toxins A1. Bk Ch7 S7.5 FA1 Example concept map: 7.4 Protecting the body FQA Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) page 1 of 4 Q2. Bk Ch7 S7.5 FQ2 a b c d Find out some of the different kinds of microflora that live in the gut. Describe the relationship between the microflora and the host. i How do the microflora benefit? ii How does the host benefit? Describe a disease that occurs in humans as a result of an imbalance of microflora in the gut. A2. Bk Ch7 S7.5 FA2 a b c d Gut bacteria (microflora) include: • Bacteriodes fragilis • Bacteriodes melaningenicus • Lactobacillus • Streptococcus faecalis • Escherichia coli. (There are at least 10 other types, which are also found.) The relationship is best described as mutualism. i The host supplies the microflora with nutrients, a stable environment, constant temperature and protection. ii The gut microflora benefit the host by: • synthesising and excreting certain vitamins (E. coli provides vitamin K) • occupying the site and so preventing pathogens from colonising • stimulating the host to produce cross-reactive antibodies which also work against pathogens. Examples: • Diarrhoea can be caused by an overgrowth of E. coli. The large intestine lining is irritated and does not absorb the usual amount of water. (Note: there are many strains of E. coli, some of which are naturally pathogenic.) • Stomach ulcers are caused by Helicobacter pylori, a spiral bacterium found in the stomach. It is able to penetrate the stomach’s protective layer of mucus and make the stomach cells more susceptible to acid and pepsin damage. • Some colonic cancers may be due in part to the products of microflora overgrowth. Q3. Bk Ch7 S7.5 FQ3 Each year some Australian city beaches are temporarily closed because of high levels of Escherichia coli (E. coli) in the water. E. coli is a bacterium that lives in the human bowel. In this relationship the bacterium causes no harm to humans. In fact, both bacterium and human benefit from their coexistence. a Outline the advantage of this symbiotic relationship to i the bacteria, and ii humans. b How do ocean beaches periodically become infected with high levels of E. coli? c Why are high levels of E. coli in the water around beaches detrimental to human health? d Describe the symptoms suffered by people suffering from E. coli infection. A3. Bk Ch7 S7.5 FA3 a b i ii E. coli bacteria benefit by having the provision of shelter and food. Humans benefit because the E. coli metabolise material in the gut, releasing vitamins K and B12. Untreated sewage has high populations of E. coli bacteria. When sewage treatment plants malfunction, untreated sewage or incompletely treated sewage may be flushed directly into the ocean causing water at ocean beaches to become infected with high levels of the bacteria. 7.4 Protecting the body FQA Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) page 2 of 4 c d The relationship between humans and E. coli is important to our well-being. However, E. coli is a pathogen when it is present in other parts of the body. E. coli infection results in diarrhoea that may contain blood. There is not much fever associated with E. coli infections but kidney failure can result in advanced cases. Q4. Bk Ch7 S7.5 FQ4 During early research on the human immunodeficiency virus (HIV), researchers were surprised to discover that some apparently healthy individuals tested positively for antibodies against the virus. What does this mean for those individuals? A4. Bk Ch7 S7.5 FA4 Healthy individuals who have tested positively for HIV must have had some exposure to the virus in the past and developed antibodies in response to the virus. Q5. Bk Ch7 S7.5 FQ5 Why is it that a rhesus-negative mother who has just given birth to a rhesus-positive baby must receive an injection of rhesus-negative antibodies? A5. Bk Ch7 S7.5 FA5 Rhesus is the name of a particular kind of antigen present on the surfaces of red blood cells. People who are rhesus-negative do not have the antigen. If they are exposed to the rhesus antigen their bodies will produce antibodies against it. If a rhesus-negative mother gives birth to a rhesus-positive baby and some of the baby’s blood mixes with the mother’s blood, as happens sometimes during childbirth, then her body will produce antibodies against the rhesus antigen. This will create a problem if she becomes pregnant at some time in the future with another rhesus-positive baby. If any of the baby’s blood leaks across the placenta into the mother’s bloodstream, her body will recognise the antigens as foreign and attack the foetus in the same way as the body would reject a transplanted organ. (New mothers in such circumstances are treated by injection to prevent this reaction from occurring. This ensures the safety of subsequent pregnancies.) Q6. Bk Ch7 S7.5 FQ6 a b Visit your local Blood Bank to find out i the differences between blood groups ii the reasons why blood type must be carefully determined before being used for transfusions. Use the information you have obtained to complete the following table, summarising the compatibility of blood groups. Blood type Antigens present on red blood cells Can donate blood to blood type Can receive blood from blood type A B AB O c i ii Which blood type is often referred to as a ‘universal donor’? Why? Which blood type is often referred to as a ‘universal recipient’? Why? 7.4 Protecting the body FQA Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) page 3 of 4 A6. Bk Ch7 S7.5 FA6 a i ii Blood groups are usually categorised according to the ABO blood grouping system. Red blood cells have different antigens on their surfaces. If A antigens are present the person is said to have blood type A; the presence of B antigens indicates blood group B; some people have both A and B antigens and therefore have blood group AB; others have blood group O because they have neither A nor B antigens on their red blood cells. It is essential that a person’s blood group is accurately determined so that blood transfusions can proceed without any problems. For example, if a person with A type blood receives blood from a donor with B type blood there will be a reaction between B antibodies present in the recipient’s blood and the donated B type red blood cells. This reaction is called agglutination and means that the blood cells clump together—this can be fatal. b c Blood type Antigens present on red blood cells Can donate blood to blood type Can receive blood from blood type A A A, AB A B B B, AB B AB A and B AB A, B, AB, O O Neither A nor B A, AB, B, O O i ii Blood group O is referred to as the universal donor because blood from people with this blood type can be transfused into a patient with any other blood group. Blood group AB is called the universal recipient because people with this blood type are able to accept blood from any other blood group. 7.4 Protecting the body FQA Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) page 4 of 4