CORE QUESTIONS #
1a) Define the term pathogen.
A pathogen is a disease-causing organism.
Examples include bacteria, viruses, fungi, and some protoctists. These organisms enter the body and cause illness or infection.
1b) State three ways in which a pathogen can be transmitted.
1. Direct contact – when infected person touches another person (for example, through cuts in the skin or sexual contact)
2. Indirect contact – through contaminated objects, water, or food that has been touched by an infected person
3. Through the air – when an infected person coughs or sneezes, tiny droplets containing pathogens spread through the air and other people breathe them in
2. Indirect contact – through contaminated objects, water, or food that has been touched by an infected person
3. Through the air – when an infected person coughs or sneezes, tiny droplets containing pathogens spread through the air and other people breathe them in
1c) Complete the table by giving three examples of body defences. For each example, describe how it defends the body.
| Body defence | How it defends the body |
|---|---|
| 1 | |
| 2 | |
| 3 |
| Body defence | How it defends the body |
|---|---|
| Skin | Acts as a physical barrier to stop pathogens entering the body. It is tough and difficult for pathogens to pass through. |
| Stomach acid | Contains hydrochloric acid which kills most pathogens that enter the body through food or drink. |
| White blood cells | Destroy pathogens that enter the body by either engulfing them (phagocytosis) or producing antibodies to kill them. |
Other acceptable answers: mucus in the airways traps pathogens; tears contain enzymes that kill bacteria; platelets help blood clot to seal cuts and prevent pathogens entering.
SUPPLEMENT QUESTIONS #
2) State what could be done to enhance the body’s defences to protect a person from a life-threatening disease.
Vaccination can be given to enhance the body’s defences.
A vaccine contains dead or weakened pathogens that are injected into the body. This causes the immune system to produce antibodies against the disease without making the person sick. If the person is later exposed to the real disease, their immune system can respond quickly to destroy the pathogens before they cause serious illness.
Other measures that enhance defences include:
- Good hygiene practices (washing hands, clean food preparation)
- Healthy diet to keep the immune system strong
- Avoiding contact with infected people
- Using antimicrobial medicines when prescribed by a doctor
3) Outline the role of the immune system in:
a) antibody production, making five key points
a) antibody production, making five key points
1. Pathogens have antigens on their surface – these are proteins that the body recognizes as foreign.
2. White blood cells called lymphocytes detect the antigens on pathogens.
3. Each lymphocyte produces a specific antibody that matches one type of antigen.
4. The antibodies bind to the antigens on the pathogen, marking them for destruction.
5. Some lymphocytes become memory cells that remain in the blood. If the same pathogen enters the body again, these memory cells quickly produce large amounts of the correct antibody to destroy it before it causes disease.
2. White blood cells called lymphocytes detect the antigens on pathogens.
3. Each lymphocyte produces a specific antibody that matches one type of antigen.
4. The antibodies bind to the antigens on the pathogen, marking them for destruction.
5. Some lymphocytes become memory cells that remain in the blood. If the same pathogen enters the body again, these memory cells quickly produce large amounts of the correct antibody to destroy it before it causes disease.
3b) phagocytosis, making three key points.
1. White blood cells called phagocytes detect pathogens in the blood or tissues.
2. The phagocyte surrounds the pathogen and engulfs it (takes it inside the cell).
3. Enzymes inside the phagocyte digest and destroy the pathogen completely.
2. The phagocyte surrounds the pathogen and engulfs it (takes it inside the cell).
3. Enzymes inside the phagocyte digest and destroy the pathogen completely.
4) Explain the process of vaccination, making three key points.
1. A vaccine containing dead or weakened pathogens is injected into the body.
2. The immune system responds by producing antibodies against the antigens on the vaccine pathogens, just as it would for a real infection. However, the person does not become ill because the pathogens in the vaccine are not strong enough to cause disease.
3. Memory cells are produced and remain in the blood. If the person is exposed to the real pathogen in the future, these memory cells quickly produce large amounts of antibodies to destroy the pathogen before it causes serious illness. This gives the person immunity to the disease.
2. The immune system responds by producing antibodies against the antigens on the vaccine pathogens, just as it would for a real infection. However, the person does not become ill because the pathogens in the vaccine are not strong enough to cause disease.
3. Memory cells are produced and remain in the blood. If the person is exposed to the real pathogen in the future, these memory cells quickly produce large amounts of antibodies to destroy the pathogen before it causes serious illness. This gives the person immunity to the disease.
5) Distinguish between passive immunity and active immunity. You should make four clear points.
Active immunity:
Passive immunity:
- The body produces its own antibodies in response to a pathogen or vaccine
- Takes time to develop (several days to weeks)
- Provides long-lasting protection (can last for years or even a lifetime)
- Examples: immunity after having a disease, immunity from vaccination
Passive immunity:
- The body receives ready-made antibodies from another source
- Provides immediate protection
- Only provides short-term protection (antibodies break down after a few weeks or months)
- Examples: antibodies from mother to baby through the placenta or breast milk, antibody injection for treatment
EXAM-STYLE QUESTIONS – CORE #
1a) Define the term transmissible disease. [2]
A transmissible disease is a disease that can be passed from one person to another.
It is caused by a pathogen (disease-causing organism) that can spread between people through various means such as direct contact, indirect contact, or through the air.
1b) Describe how a pathogen is transmitted by:
i) direct contact [2]
i) direct contact [2]
Direct contact transmission happens when an infected person physically touches another person, and pathogens pass from one person to the other.
This can happen through:
- Touching an infected person’s skin (especially if there are cuts or wounds)
- Sexual contact between an infected and uninfected person
- Blood-to-blood contact (for example, sharing needles)
- Mother to baby during childbirth
Example diseases: HIV/AIDS, some types of hepatitis, sexually transmitted infections
1b ii) indirect contact. [2]
[Total: 4]
[Total: 4]
Indirect contact transmission happens when pathogens pass from an infected person to another person through a non-living object or substance.
This can happen through:
- Contaminated water – pathogens from infected person enter water supply, others drink the water
- Contaminated food – pathogens on food that has been touched or prepared by infected person
- Contaminated objects – pathogens left on doorknobs, utensils, or other objects that others touch
- Insect vectors – insects like mosquitoes bite infected person, then bite another person and transfer pathogens
Example diseases: cholera (through water), malaria (through mosquitoes), food poisoning
SUPPLEMENT QUESTION #
2) Explain the effect of cholera bacteria on the body. [6]
Cholera is caused by the bacterium Vibrio cholerae which affects the small intestine.
How cholera bacteria affect the body:
1. The cholera bacteria are usually transmitted through contaminated water or food. When a person drinks infected water, the bacteria enter the digestive system.
2. The bacteria reach the small intestine and attach to the intestine wall.
3. The bacteria produce a toxin (poison) that affects the cells lining the small intestine.
4. This toxin causes the intestine cells to release large amounts of water and salts (ions) into the intestine cavity.
5. This leads to severe, watery diarrhea. The person can lose several liters of water per day.
6. The loss of water and salts causes dehydration, which can be fatal if not treated quickly. Symptoms include extreme thirst, weakness, low blood pressure, and in severe cases, death.
Treatment: Cholera is treated by replacing the lost water and salts through oral rehydration therapy (drinking water with added salts and glucose) or intravenous fluids in severe cases. Antibiotics can also help kill the bacteria.
How cholera bacteria affect the body:
1. The cholera bacteria are usually transmitted through contaminated water or food. When a person drinks infected water, the bacteria enter the digestive system.
2. The bacteria reach the small intestine and attach to the intestine wall.
3. The bacteria produce a toxin (poison) that affects the cells lining the small intestine.
4. This toxin causes the intestine cells to release large amounts of water and salts (ions) into the intestine cavity.
5. This leads to severe, watery diarrhea. The person can lose several liters of water per day.
6. The loss of water and salts causes dehydration, which can be fatal if not treated quickly. Symptoms include extreme thirst, weakness, low blood pressure, and in severe cases, death.
Treatment: Cholera is treated by replacing the lost water and salts through oral rehydration therapy (drinking water with added salts and glucose) or intravenous fluids in severe cases. Antibiotics can also help kill the bacteria.
