Download 7.4 Protecting the body – Further questions and answers Q1. Bk Ch7

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