Diseases & Immunity (Cambridge (CIE) IGCSE Biology)

(i)

Describe and explain the effects of cholera bacteria on the gut.

[4]

(ii)

Suggest one treatment for cholera.

[1]

What term is used to describe ‘disease-causing organisms’?

Fig. 1 shows some virus particles that cause the transmissible disease, influenza.

Fig. 1

Suggest how the virus particles that cause influenza are transmitted from one person to another.

Describe the defences of the body which prevent or fight infection.

Explain why antibiotics are not successful in treating influenza.

Eating food contaminated by bacteria can cause illness.

This type of illness is called food poisoning.

Fig. 1 shows the number of cases of food poisoning per 100 000 people in the population in one country.

Fig. 1

(i)

State the year with the highest number of cases of food poisoning in Fig. 1.

[1]

(ii)

State the number of cases of food poisoning per 100 000 people in the population in the year 1996 in Fig. 1.

[1]

(iii)

Describe the trend in the number of cases of food poisoning between 2003 and 2011 in Fig. 1.

[3]

Food poisoning is caused by different types of bacteria.

A common type of bacterium that causes food poisoning is Campylobacter jejuni.

State the genus of this species.

Food poisoning can result in vomiting and diarrhoea.

Outline the treatment of diarrhoea.

The body has several defence mechanisms against bacteria.

Table 1 shows three types of defence mechanism.

The word list gives examples of these defence mechanisms.

In Table 1 write the examples under the correct type of defence.

Use each word once only.

Table 1

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White blood cells form part of the immune system in the human body which provides protection against infection by pathogens.

Outline the possible responses of these white blood cells to an infection by pathogens.

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Being vaccinated is another way to gain protection against infection by pathogens.

Describe how vaccines provide protection against infection by pathogens.

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The measles vaccine will not give a child immunity against the influenza virus.

Explain the reason for this.

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The flu is an example of a disease against which we typically don't build immunity; this is the main reason why we need to get vaccinated against flu regularly.

Explain why it is difficult to develop immunity against certain pathogens, such as the influenza virus.

Breastfeeding is an example of passive immunity which provides the baby with short-term protection against pathogens.

Explain why passive immunity only provides short-term protection against pathogens.

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Not all babies are breastfed.

Suggest one way in which these babies may gain immunity against pathogens.

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An American TV crew visited a remote tribe in the Brazilian rainforest to make a documentary. 

Two weeks after the crew's visit, six members of the tribe died of influenza and many more were seriously ill.

The members of the TV crew did not show symptoms of influenza during their visit, but members of the remote tribe died from the disease.

Suggest an explanation for this. 

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The Center for Disease Control and Prevention estimated that 3.55 × 10⁷ individuals were infected with influenza in the United States during the 2018-19 'flu season. 

Of those individuals affected, an estimated 3.42 × 10⁴ died, sadly.

Based on these estimated figures, calculate the percentage of people infected with influenza that died from the disease during the 2018-19 'flu season.

Show your working and give your answer to two decimal places.

Streptococcus pyogenes is a pathogenic bacteria that spreads through direct contact with discharges from the nose and throat, as well as through open wounds and sores on the skin of infected people.

In the 19th century, many women died shortly after childbirth due to a disease called puerperal fever, which is caused by an infection of S. pyogenes. At the time, it was common practice for doctors to dissect dead bodies in order to study human anatomy and then move straight onto delivering babies immediately after.

Suggest an explanation for the frequent deaths of women after childbirth due to puerperal fever.

Table 1 shows the number of births and deaths at a hospital between 1841 and 1846.

Table 1

Calculate and state the percentage change in the number of deaths between 1841 and 1846.

Show your working and give your answer to the nearest whole number.

In 1847 a handwashing policy was introduced at the hospital from part (b) which stated that doctors should wash their hands before delivering babies in the maternity ward. This policy was strictly enforced in 1848.

Fig. 1 shows the death rate of mothers from puerperal fever between 1846 and 1848.

Fig. 1

Describe and explain the data from January 1847 to July 1848.

Other than washing their hands, suggest two other hygiene practices that doctors in hospitals should carry out in order to avoid the spread of pathogens to their patients.

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CGRP is a protein found in the human brain. High levels of CGRP has been linked to the occurrence of migraines in sufferers. A possible treatment under investigation involves injecting mice with human CGRP.

Explain how the immune system of mice would respond to the CGRP injection.

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CGRP binds to receptors in the brain that triggers blood vessels to dilate. The dilation of blood vessels is responsible for the intense pain associated with migraines.

The substances produced by the immune system of mice, after the CGRP injection, are extracted and modified before being sold as medication. When administered to migraine sufferers, these substances will bind to CGRP proteins in the brain.

Suggest how this may act as a treatment for migraines.

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Complete the graph in Fig. 1 to show how the number of antibodies changes when a vaccinated person becomes infected with a live pathogen. 

Fig. 1

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After many people were vaccinated against Covid-19, a new variant of the virus emerged that had different shaped antigens to the first version of the virus. 

This caused the vaccine to be less effective against the virus.

Explain why having different shaped antigens caused the vaccine to be less effective against the virus.

Table 1 shows information about the number of deaths from malaria in a particular area of Africa. 

Table 1

Complete Fig. 1 using data from Table 1.

Fig. 1

Malaria is spread by the female Anopheles mosquito when they break through the skin of an uninfected person during a blood meal.

Explain how the skin acts as a mechanical barrier against disease.

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Once the mechanical barrier formed by the skin is broken, the malaria pathogen enters the blood.

Outline the defence mechanism that will come into effect once a pathogen enters the blood.

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Compare active and passive immunity with each other.