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Understand Disease and the Immune System

Worksheet Overview

QUESTION 1 of 10

Your body is an amazing design - there are things that are trying to harm it coming from everywhere: bacteria, viruses, blood-sucking bats and killer plants from outer space! But, thanks to years of perfecting the design, your body has a load of defence mechanisms to help you to kill off any foreign invaders. These mechanisms are so good that they can tell if you have an organ transplant and they will try and kill it (because it's not your own organ and it doesn't belong in your body!). To help with this, if you have an organ transplant most people have to take drugs for the rest of their lives to slow down their immune system so it doesn't kill off the foreign organ-invader. We will take a look at how your body keeps you safe in this worksheet. 

 

Microorganisms are tiny living organisms, usually made from only one cell. Some are quite useful, such as yeast that is used in baking, but most are quite dangerous, as they can cause disease. Microorganisms that cause disease are called pathogens. There are four types of pathogens:

 

Bacteria that cause diseases such as cholera, tuberculosis, salmonella, tetanus and pneumonia.

Viruses that cause AIDS, measles, rubella, warts and flu.

Fungi that cause athlete's foot, thrush and even throat infections.

Protozoa that cause dysentery and malaria.


Diseases that can spread from person to person are called contagious.

 Vector animals, like the mosquito and the house fly, carry microorganisms that cause a disease but they do not suffer from the disease themselves. An example of this is malaria, which is caused by the protozoan Plasmodium falciparum, which is transmitted to humans when they are bitten by female mosquitoes in some tropical areas. This parasite feeds on red blood cells from humans causing fever which can often be fatal.

 

Fortunately, our body can fight pathogens with the help of white blood cells. This is active immunity as our body actively tries to fight disease. Medical research has developed antibiotics and vaccines to save even more lives. This is called passive immunity.

 

Let's move on to the questions now.

What do we call microorganisms that cause disease?

Which of the statements below describe vectors?

Vectors are animals that carry a disease while not suffering from it

The parasites that vectors carry feed on red blood cells in humans

Spiders are vectors that carry malaria

Vectors are diagrams used in maths

Cancer is an illness, although it is rarely caused by microorganisms. An example is cervical cancer, which may be caused by a strain of a virus called HPV. It is caused by cells which divide out of control. Benign tumours are not cancerous.

 

Do you know the scientific name for cancerous tumours? 

Use your common sense or any previous knowledge you have to answer the following question.

 

What can we do to help our body fight disease? 

We should expose ourselves to the Sun a lot, as well as very cold weather

We should consume lots of vitamins

We should eat food that contains iron

We should maintain a healthy lifestyle

The diagram below shows the ways that the body uses to prevent microorganisms from entering, as well as defence 'weapons' that it uses once pathogens have entered.

 

 

Tick any conclusions that you can derive from the diagram about how the body fights pathogens before they enter.

Tears have bacteria killing substances

The skin protects the body on the outside

Antibodies are produced by white blood cells

Defence cells are called B-lymphocytes

White blood cells fight disease in three different ways:

They produce antibodies.

They produce antitoxins - some kind of an antidote for the toxins (poisonous chemicals) produced by microorganisms.

They engulf (eat) pathogens -  this is called phagocytosis.

 

Pathogens have chemical structures on their surface that are specific to each type of pathogen - they are called antigens. White blood cells produce antibodies that surround and disarm the pathogen by destroying the antigens. Here are two diagrams that show this process.

 

image of antibody specificity Image of a phagocyte

 

Study the diagrams and the options below.

The shape of the antibody depends on the shape of the antigen

The shape of the antigen depends on the shape of the antibody

Each type of antibody is made to disarm antigens produced by specific types of pathogens

Blue-purple antibodies are the best

Image of phogocitosis

 

Can you guess the name of the process illustrated in the diagram above? Think about the information that was given in the previous question.

An epidemic is when a disease spreads among the population of an area or country. An epidemic becomes a pandemic when the disease spreads across the world.

 

 A graph of the swine flu pandemic

Study the graph showing how the swine flu pandemic affected the United States of America.

 

How many people were infected between the 15th of May 2009 (05/15/09) and the 10th of July (07/10/09)?

When our white blood cells make antibodies to fight a disease, it can take some time, like two weeks. However, some diseases would develop really quickly and could even kill us during this time, so scientists have developed vaccines. Injection of a vaccine is called vaccination or immunisation and is passive immunity, because our immune system receives some help. 

A vaccine contains a weak or dead form of the pathogen, which white blood cells still recognise as foreign to our body, so they produce antibodies (this takes a few weeks as mentioned above). If we are infected by the real pathogen after being vaccinated though, white blood cells can make antibodies within a couple of days, because they are familiar with the pathogen. 

The graph shows clearly that the secondary response (making antibodies for the second exposure to the pathogen) is much higher than the primary response.

 

A graph showing the importance of vaccination.

 

What can be said to be true from this graph?

Primary response is higher than the secondary

The curve of the secondary response is steeper than that of the primary response

A steeper curve means antibody production is higher and faster

A primary response is only triggered by a vaccine

Antibiotics are drugs that are developed to fight bacteria. They cannot kill viruses.

 

What statements below are true of viruses?

We can kill viruses with antibiotics

All viruses can be tackled with vaccines

Viruses use the host's cells to reproduce

Viruses mutate (change DNA) frequently so new drugs have to be developed regularly to tackle the new form of the virus

  • Question 1

What do we call microorganisms that cause disease?

CORRECT ANSWER
pathogens
EDDIE SAYS
It's always hard when you have no options to choose from! How did you do with the spelling of this word? Pathogens are microorganisms that cause disease. They include bacteria, viruses, fungi and protists.
  • Question 2

Which of the statements below describe vectors?

CORRECT ANSWER
Vectors are animals that carry a disease while not suffering from it
The parasites that vectors carry feed on red blood cells in humans
EDDIE SAYS
OK, so technically there were three correct options here because vectors are indeed used in maths! However, in this context of the word, it is not a correct description so it wouldn't be allowed! Vectors are animals that carry a disease, while they do not suffer from it. An example is mosquitoes that carry a parasite that causes malaria, or fleas that carry the bubonic plague.
  • Question 3

Cancer is an illness, although it is rarely caused by microorganisms. An example is cervical cancer, which may be caused by a strain of a virus called HPV. It is caused by cells which divide out of control. Benign tumours are not cancerous.

 

Do you know the scientific name for cancerous tumours? 

CORRECT ANSWER
malignant
EDDIE SAYS
Did you know this one or did you do a bit of research to find the answer? Cancerous tumours are called malignant. This means that they are not enclosed by a membrane and are able to spread to different parts of the body.
  • Question 4

Use your common sense or any previous knowledge you have to answer the following question.

 

What can we do to help our body fight disease? 

CORRECT ANSWER
We should consume lots of vitamins
We should eat food that contains iron
We should maintain a healthy lifestyle
EDDIE SAYS
These were really common sense, weren't they? A healthy lifestyle and a balanced diet (including plenty of vitamins and minerals) are very important. They make you more healthy in general and so, when you become ill, you are stronger and more able to fight off the pathogens.
  • Question 5

The diagram below shows the ways that the body uses to prevent microorganisms from entering, as well as defence 'weapons' that it uses once pathogens have entered.

 

 

Tick any conclusions that you can derive from the diagram about how the body fights pathogens before they enter.

CORRECT ANSWER
Tears have bacteria killing substances
The skin protects the body on the outside
EDDIE SAYS
What a lot there was to think about here. All four sentences describe how the body fights disease, but only options one and two refer to ways that pathogens are fought before they enter the body. We call these non-specific as they kill all pathogens and not only specific ones.
  • Question 6

White blood cells fight disease in three different ways:

They produce antibodies.

They produce antitoxins - some kind of an antidote for the toxins (poisonous chemicals) produced by microorganisms.

They engulf (eat) pathogens -  this is called phagocytosis.

 

Pathogens have chemical structures on their surface that are specific to each type of pathogen - they are called antigens. White blood cells produce antibodies that surround and disarm the pathogen by destroying the antigens. Here are two diagrams that show this process.

 

image of antibody specificity Image of a phagocyte

 

Study the diagrams and the options below.

CORRECT ANSWER
The shape of the antibody depends on the shape of the antigen
Each type of antibody is made to disarm antigens produced by specific types of pathogens
EDDIE SAYS
This was a pretty tough question so don't despair if you didn't get both the options right. Antibodies are made after the pathogens (with their antigens) enter the body, so their shape fits that of the antigen. Therefore, pathogens are fought by specific antibodies. If the antibodies were generalised, then they could accidentally harm your body cells. This is why the immune system needs to be specific about what it attacks.
  • Question 7

Image of phogocitosis

 

Can you guess the name of the process illustrated in the diagram above? Think about the information that was given in the previous question.

CORRECT ANSWER
phagocytosis
EDDIE SAYS
Well done if you got this one correct - and spelled it right too! Some white blood cells specialise in engulfing (eating) pathogens. This process is called phagocytosis.
  • Question 8

An epidemic is when a disease spreads among the population of an area or country. An epidemic becomes a pandemic when the disease spreads across the world.

 

 A graph of the swine flu pandemic

Study the graph showing how the swine flu pandemic affected the United States of America.

 

How many people were infected between the 15th of May 2009 (05/15/09) and the 10th of July (07/10/09)?

CORRECT ANSWER
32,500
32 500
32500
EDDIE SAYS
Did you find this a bit confusing because the dates were written differently? This is an American graph and they write their dates in a different order to the way we write them in the UK. They put the month before the day, so they would write the 15th May as 05/15. In order to find the answer, you have to subtract the number of cases on the 15th of May (5,000) from the number of cases on the 10th of July (37,500), which leaves 32,500.
  • Question 9

When our white blood cells make antibodies to fight a disease, it can take some time, like two weeks. However, some diseases would develop really quickly and could even kill us during this time, so scientists have developed vaccines. Injection of a vaccine is called vaccination or immunisation and is passive immunity, because our immune system receives some help. 

A vaccine contains a weak or dead form of the pathogen, which white blood cells still recognise as foreign to our body, so they produce antibodies (this takes a few weeks as mentioned above). If we are infected by the real pathogen after being vaccinated though, white blood cells can make antibodies within a couple of days, because they are familiar with the pathogen. 

The graph shows clearly that the secondary response (making antibodies for the second exposure to the pathogen) is much higher than the primary response.

 

A graph showing the importance of vaccination.

 

What can be said to be true from this graph?

CORRECT ANSWER
The curve of the secondary response is steeper than that of the primary response
A steeper curve means antibody production is higher and faster
EDDIE SAYS
Did you spot the trend in this graph? The curve becomes much steeper after the secondary response. This means that antibody production is faster and higher. A primary response can be caused by a vaccine or the first exposure to the real pathogen.
  • Question 10

Antibiotics are drugs that are developed to fight bacteria. They cannot kill viruses.

 

What statements below are true of viruses?

CORRECT ANSWER
Viruses use the host's cells to reproduce
Viruses mutate (change DNA) frequently so new drugs have to be developed regularly to tackle the new form of the virus
EDDIE SAYS
There were two correct options here. Did you get them both? Viruses use the host's cells to reproduce and they also mutate (change DNA) frequently so new drugs have to be developed regularly to tackle the new form of the virus. These two factors, make it much harder to treat a virus than a bacterial infection. This is a complicated topic, so well done for getting to the end of this activity. Hopefully, you feel more confident with the difference between bacteria and viruses, and how our immune system works to protect us.
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