AQA GCSE Biology · 4.3

Infection and response

Exam-style questions with answers for 4.3 Infection and response in AQA GCSE Biology (spec 8461). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All questions and answers

Question 1 · Spec 4.3.1.1 · Pathogens
What is a pathogen? [1 mark]
Answer:
A microorganism that causes infectious disease.
Question 2 · Spec 4.3.1.1 · Pathogens
Name the four types of pathogen. [2 marks]
Answer:
Bacteria and viruses (1); protists and fungi (1).
Question 3 · Spec 4.3.1.1 · Pathogens
State three ways pathogens can be spread. [3 marks]
Answer:
By direct contact (1); by water (1); by air (1).
Question 4 · Spec 4.3.1.1 · Pathogens
How do bacteria and viruses make us ill? [2 marks]
Answer:
Bacteria reproduce rapidly and may produce toxins that damage tissues (1); viruses live and reproduce inside cells, causing cell damage (1).
Question 5 · Spec 4.3.1.1 · Pathogens
State two ways to reduce the spread of disease. [2 marks]
Answer:
Any two from: hygiene, such as hand washing (1); isolating infected individuals (1); destroying or controlling vectors (1); vaccination (1).
Question 6 · Spec 4.3.1.2 · Viral diseases
Describe the symptoms and spread of measles. [2 marks]
Answer:
Fever and a red skin rash (1); spread by inhalation of droplets from sneezes and coughs (1).
Question 7 · Spec 4.3.1.2 · Viral diseases
How is HIV spread? [2 marks]
Answer:
By sexual contact (1); or exchange of body fluids such as blood, for example when drug users share needles (1).
Question 8 · Spec 4.3.1.2 · Viral diseases
How does HIV lead to AIDS? [2 marks]
Answer:
The virus attacks the body's immune cells (1); late-stage HIV (AIDS) occurs when the immune system is so damaged it cannot fight other infections or cancers (1).
Question 9 · Spec 4.3.1.2 · Viral diseases
Describe the effect of tobacco mosaic virus (TMV) on plants. [2 marks]
Answer:
It causes a mosaic pattern of discoloration on the leaves (1); which reduces photosynthesis, so growth is reduced (1).
Question 10 · Spec 4.3.1.3 · Bacterial diseases
Describe the symptoms and treatment of gonorrhoea. [2 marks]
Answer:
A thick yellow or green discharge from the vagina or penis and pain on urinating (1); treated with antibiotics, though many strains are now resistant (1).
Question 11 · Spec 4.3.1.3 · Bacterial diseases
How can the spread of gonorrhoea be controlled? [2 marks]
Answer:
Treatment with antibiotics (1); use of a barrier method of contraception such as a condom (1).
Question 12 · Spec 4.3.1.3 · Bacterial diseases
Describe how Salmonella food poisoning is spread and its symptoms. [2 marks]
Answer:
Eating undercooked food or food prepared in unhygienic conditions (1); fever, abdominal cramps, vomiting and diarrhoea caused by bacterial toxins (1).
Question 13 · Spec 4.3.1.3 · Bacterial diseases
How is the spread of Salmonella controlled in the UK? [1 mark]
Answer:
Poultry are vaccinated against Salmonella.
Question 14 · Spec 4.3.1.4 · Fungal diseases
Describe the symptoms of rose black spot. [2 marks]
Answer:
Purple or black spots on leaves, which turn yellow and drop early (1); this reduces photosynthesis and growth (1).
Question 15 · Spec 4.3.1.4 · Fungal diseases
How is rose black spot treated? [2 marks]
Answer:
Using fungicides (1); and removing and destroying the affected leaves (1).
Question 16 · Spec 4.3.1.5 · Protist diseases
How is malaria spread? [2 marks]
Answer:
By mosquitoes, which act as vectors (1); the protist has a life cycle that includes the mosquito (1).
Question 17 · Spec 4.3.1.5 · Protist diseases
State two ways to control the spread of malaria. [2 marks]
Answer:
Any two from: preventing mosquitoes breeding (1); using mosquito nets (1); insecticides (1); antimalarial drugs (1).
Question 18 · Spec 4.3.1.6 · Non-specific defences
Describe two non-specific defences of the human body. [2 marks]
Answer:
Any two from: skin acts as a barrier (1); the nose traps particles in hairs and mucus (1); cilia in the trachea and bronchi move mucus up to the throat (1); stomach acid kills pathogens (1).
Question 19 · Spec 4.3.1.6 · White blood cells
State three ways white blood cells defend the body. [3 marks]
Answer:
Phagocytosis, engulfing pathogens (1); producing antibodies (1); producing antitoxins (1).
Question 20 · Spec 4.3.1.6 · White blood cells
Why are antibodies specific? [1 mark]
Answer:
Each antibody has a shape that is complementary to a particular antigen on one type of pathogen.
Question 21 · Spec 4.3.1.7 · Vaccination
Explain how vaccination protects against disease. [3 marks]
Answer:
A small quantity of dead or inactive pathogen is injected (1); this stimulates white blood cells to produce antibodies (1); if the same pathogen re-enters, antibodies are produced rapidly, preventing infection (1).
Question 22 · Spec 4.3.1.7 · Vaccination
What is herd immunity? [2 marks]
Answer:
If a large proportion of the population is immune, the spread of the pathogen is reduced (1); this protects people who are not vaccinated (1).
Question 23 · Spec 4.3.1.8 · Antibiotics
Why can antibiotics not be used to treat viral diseases? [1 mark]
Answer:
Viruses live and reproduce inside cells, so it is difficult to kill them without damaging body tissues; antibiotics only kill bacteria.
Question 24 · Spec 4.3.1.8 · Painkillers
What is the difference between antibiotics and painkillers? [2 marks]
Answer:
Antibiotics kill infective bacteria inside the body (1); painkillers only treat the symptoms and do not kill pathogens (1).
Question 25 · Spec 4.3.1.8 · Antibiotics
Why is the emergence of antibiotic-resistant strains a concern? [1 mark]
Answer:
Some infections, such as MRSA, become very hard to treat.
Question 26 · Spec 4.3.1.9 · Drug development
Name the original sources of digitalis, aspirin and penicillin. [3 marks]
Answer:
Digitalis from foxgloves (1); aspirin from willow (1); penicillin from Penicillium mould, discovered by Alexander Fleming (1).
Question 27 · Spec 4.3.1.9 · Drug development
State the three things new drugs are tested for. [3 marks]
Answer:
Toxicity (1); efficacy (1); dose (1).
Question 28 · Spec 4.3.1.9 · Drug development
Describe preclinical testing of drugs. [2 marks]
Answer:
Drugs are tested in the laboratory (1); using cells, tissues and live animals (1).
Question 29 · Spec 4.3.1.9 · Drug development
Describe clinical trials. [2 marks]
Answer:
Very low doses are first given to healthy volunteers to test for toxicity (1); then patients are given the drug to find the optimum dose (1).
Question 30 · Spec 4.3.1.9 · Drug development
What is a double blind trial? [2 marks]
Answer:
Patients are randomly given the drug or a placebo (1); neither the patients nor the doctors know who received which until the end (1).
Question 31 · Spec 4.3.1.9 · Drug development
Why are results peer reviewed before publication? [1 mark]
Answer:
To check the results are valid and prevent false claims.
Question 32 · Spec 4.3.2.1 · Monoclonal antibodies · Higher only
What are monoclonal antibodies? [1 mark]
Answer:
Identical antibodies produced from a single clone of cells, specific to one binding site on one protein antigen.
Question 33 · Spec 4.3.2.1 · Monoclonal antibodies · Higher only
Describe how monoclonal antibodies are produced. [3 marks]
Answer:
A mouse is injected with an antigen, stimulating lymphocytes to make an antibody (1); the lymphocytes are combined with a tumour cell to make a hybridoma cell (1); the hybridoma cells divide and make the antibody, which is collected and purified (1).
Question 34 · Spec 4.3.2.1 · Monoclonal antibodies · Higher only
Why are lymphocytes fused with tumour cells? [1 mark]
Answer:
Lymphocytes make antibodies but do not divide, while tumour cells divide rapidly.
Question 35 · Spec 4.3.2.2 · Monoclonal antibodies · Higher only
State three uses of monoclonal antibodies. [3 marks]
Answer:
Any three from: pregnancy tests (1); measuring levels of hormones and chemicals in blood, or detecting pathogens (1); locating specific molecules in cells or tissue using a fluorescent dye (1); treating diseases such as cancer (1).
Question 36 · Spec 4.3.2.2 · Monoclonal antibodies · Higher only
Explain how a pregnancy test detects pregnancy. [2 marks]
Answer:
Antibodies on the stick bind to the hormone HCG in urine (1); this produces a coloured line showing the woman is pregnant (1).
Question 37 · Spec 4.3.2.2 · Monoclonal antibodies · Higher only
How can monoclonal antibodies be used to treat cancer? [2 marks]
Answer:
They can be bound to a radioactive substance, toxic drug or chemical that stops cells dividing (1); the antibody delivers it to the cancer cells without harming other cells (1).
Question 38 · Spec 4.3.2.2 · Monoclonal antibodies · Higher only
Why are monoclonal antibodies not as widely used as hoped? [1 mark]
Answer:
They create more side effects than expected.
Question 39 · Spec 4.3.3.1 · Plant disease
Name two plant diseases caused by pathogens. [2 marks]
Answer:
Any two from: tobacco mosaic virus (1); black spot (fungus) (1); aphids (insects) as pests (1).
Question 40 · Spec 4.3.3.1 · Plant disease
What symptoms do plants show with nitrate deficiency and magnesium deficiency? [2 marks]
Answer:
Nitrate deficiency: stunted growth, as nitrates are needed for protein synthesis (1); magnesium deficiency: chlorosis (yellow leaves), as magnesium is needed to make chlorophyll (1).
Question 41 · Spec 4.3.3.1 · Plant disease · Higher only
State three signs that a plant may be diseased. [3 marks]
Answer:
Any three from: stunted growth (1); spots on leaves (1); areas of decay (rot) (1); growths (1); malformed stems or leaves (1); discoloration (1); presence of pests (1).
Question 42 · Spec 4.3.3.1 · Plant disease · Higher only
State two ways plant diseases can be identified. [2 marks]
Answer:
Any two from: using a gardening manual or website (1); taking infected plants to a laboratory to identify the pathogen (1); using testing kits containing monoclonal antibodies (1).
Question 43 · Spec 4.3.3.2 · Plant defences
State two physical defences of plants. [2 marks]
Answer:
Any two from: cellulose cell walls (1); a tough waxy cuticle on leaves (1); layers of dead cells on the surface, such as bark (1).
Question 44 · Spec 4.3.3.2 · Plant defences
State two chemical defences of plants. [2 marks]
Answer:
Antibacterial chemicals, such as those made by mint and witch hazel (1); poisons to deter herbivores, such as in foxgloves (1).
Question 45 · Spec 4.3.3.2 · Plant defences
State two mechanical adaptations of plants against herbivores. [2 marks]
Answer:
Any two from: thorns and hairs (1); leaves that droop or curl when touched (1); mimicry to trick animals (1).
Question 46 · Spec 4.3.1.6 · Immune system
Why do we not usually catch the same disease twice? [2 marks]
Answer:
Memory cells remain after the first infection (1); so antibodies are made faster and in greater numbers the next time (1).
Question 47 · Spec 4.3.1.2 · Viral diseases
Why is there no treatment to cure measles? [1 mark]
Answer:
It is a virus and antibiotics do not work; it is prevented by vaccinating young children.
Question 48 · Spec 4.3.1.8 · Antibiotics
Why should patients complete their course of antibiotics? [1 mark]
Answer:
To kill all the bacteria, so none survive to mutate and become resistant.
Question 49 · Spec 4.3.1.7 · Vaccination
Give one advantage and one disadvantage of vaccination. [2 marks]
Answer:
Advantage: controls and can eradicate diseases (1). Disadvantage: some people have side effects or a bad reaction (1).
Question 50 · Spec 4.3.1.2 · Viral diseases
How is tobacco mosaic virus spread? [1 mark]
Answer:
By contact between plants, for example on people's hands or tools, and by insect vectors.

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