AQA Biology GCSE Topic 3: Infection and Response

Flashcards for AQA Biology GCSE Topic 3: Infection and Response

Pathogens

Microorganisms that cause infectious disease; includes viruses, bacteria, protists, and fungi.

Viruses

Very small pathogens that move into cells and use the cell's biochemistry to make copies of itself, leading to cell bursting and illness.

Bacteria

Small pathogens that multiply quickly through binary fission and produce toxins that can damage cells.

Protists

Pathogens that are parasitic, using humans and animals as hosts, living on and inside them, causing damage.

Fungi

Pathogens that can be single-celled or have a body made of hyphae and produce spores which can spread to other organisms.

Direct contact

Touching contaminated surfaces; a way pathogens can be spread.

By water

Drinking or coming into contact with dirty water; a way pathogens can be spread.

By air

Pathogens carried in the air and breathed in, such as through droplet infection.

Improving hygiene

Hand washing, using disinfectants, isolating raw meat; ways to improve hygiene and limit the spread of pathogens.

Removing vectors

Using pesticides or insecticides and removing their habitat; ways to remove vectors of disease.

Vaccination

Injecting a small amount of a harmless pathogen into an individual’s body so they become immune.

Measles symptoms

Fever and red skin rash; can lead to pneumonia, encephalitis and blindness.

How Measles is spread

Droplet infection

Measles prevention

Vaccinations for young children.

HIV symptoms

Initially flu-like symptoms, then attacks the immune system and leads to AIDS.

HIV spread

Sexual contact or exchange of bodily fluids.

HIV prevention

Use of condoms, not sharing needles, screening blood, and bottle-feeding for mothers with HIV.

Tobacco mosaic virus symptoms

Discolouration of the leaves resulting in the reduction of yield

Tobacco mosaic virus spread

Contact between diseased and healthy plants, insects act as vectors.

Tobacco mosaic virus prevention

Good field hygiene and pest control, growing TMV-resistant strains.

Salmonella food poisoning symptoms

Fever, stomach cramps, vomiting, diarrhoea (caused by the toxins they secrete).

Salmonella food poisoning spread

Found in raw meat and eggs, unhygienic conditions.

Salmonella food poisoning prevention

Vaccinating poultry, keeping raw meat away from cooked food, washing hands and surfaces, cooking food thoroughly.

Gonorrhoea symptoms

Thick yellow or green discharge, pain when urinating.

Gonorrhoea spread

Spread through unprotected sexual contact.

Gonorrhoea prevention

Using contraception such as condoms and antibiotics.

Rose black spot symptoms

Purple or black spots on leaves, reduces photosynthesis area, leaves turn yellow and drop early.

Rose black spot spread

Spores are spread in water or by wind.

Rose black spot prevention

Using fungicides or stripping the plant of affected leaves.

Malaria symptoms

Fevers and shaking (when the protists burst out of blood cells).

Malaria vector

Female Anopheles mosquito.

Malaria prevention

Using insecticide coated nets, removing stagnant water, taking antimalarial drugs.

Skin

Acts as a physical barrier; produces antimicrobial secretions; skin flora compete with bad microorganisms.

Nose

Hairs and mucus that prevent particles from entering the lungs.

Trachea and Bronchi

Secrete mucus to trap pathogens; cilia waft mucus upwards to be swallowed.

Stomach

Produces hydrochloric acid that kills pathogens in mucus, food, and drink.

Phagocytosis

Destroying pathogens by engulfing and consuming them.

Producing antibodies

Each pathogen has an antigen on their surface, which is a structure which a specific complementary antibody can bind to, clumping pathogens together.

Producing antitoxins

Neutralise toxins released by pathogens by binding to them.

Vaccination

Making an individual immune to a certain disease before they have been infected.

How vaccinations work

Vaccinations replicate the first infection so that when the person is exposed to the real disease they do not feel any symptoms, just like in a secondary infection.

Antibiotics

Medicines that kill bacterial pathogens inside the body, without damaging body cells.

Painkillers

Treat the symptoms of the disease, rather than the cause.

Antibiotic resistance

Mutations during reproduction result in certain bacteria no longer being killed by antibiotics.

Preventing antibiotic resistance

Stop overusing antibiotics and finishing courses of antibiotics.

New drugs

Tested for toxicity, efficacy and dose, using preclinical and clinical trials.

Plants and drugs

Chemicals that plants use to kill pests and pathogens can be used to treat symptoms of human diseases.

Examples of Drugs from Plants

Aspirin (from willow) and Digitalis (from foxgloves).

Penicillin

Alexander Fleming found that Penicillium mould was producing a substance that killed bacteria.

Preclinical testing

Using cells, tissues and live animals.

Clinical testing

Using volunteers and patients.

Monoclonal antibodies

Identical antibodies, produced from the same immune cell that can bind to only one protein antigen.

Uses of monoclonal antibodies

Pregnancy tests, measuring hormones, research, and treating disease.

Production of monoclonal antibodies

Lymphocytes (from mice) combined with tumor cells to form hybridoma cells, which are cloned to produce antibodies.

hCG

Hormone present in the urine of pregnant women.

Monoclonal antibodies for cancer treatment

Target tumor markers to stimulate the immune system, block growth-stimulating molecules, or transport toxic substances to cancer cells.

Signs of plant diseases

Stunted growth, spots on leaves, areas of decay, abnormal growths.

Identifying plant diseases

Gardening manual, laboratory observation, or monoclonal antibody testing.

Plant diseases to learn

Tobacco mosaic virus, black spot, and aphids.

Nitrate deficiency

Nitrates are needed to convert sugars into protein.

Magnesium deficiency

Magnesium is needed to make chlorophyll.

Physical plant defenses

Tough waxy cuticle, cellulose cell walls, and layers of dead cells.

Chemical plant defenses

Poisons and antibacterial compounds.

Mechanical plant defenses

Thorns, hairs, drooping/curling leaves, and mimicry.