B3 - Infection And Response

Question 1

Pathogens

Answer 1

Microorganisms which enter the body and cause communicable disease, e.g. bacteria, viruses, fungi, protists. These can be spread in many different ways:
- water, e.g. cholera
- air, e.g. influenza
- direct contact, e.g. athlete’s foot

Question 2

Bacteria

Answer 2

Small cells that reproduce very quickly in the body; they produce toxins which make damage cells and tissue, and cause feelings of sickness

Question 3

Viruses

Answer 3

Very small organisms that can reproduce quickly in the body; they live inside of cells, where they replicate before bursting out the cell, releasing new viruses

Question 4

Fungi

Answer 4

Organisms that either are single-celled or have hyphae which penetrate the human skin or the surface of plants, causing disease. The hyphae can produce spores which can be spread to other plants and animals

Question 5

Protists

Answer 5

All are eukaryotes, and some are parasites which live on or inside other organisms and can cause them damage: they’re often transferred to the organism by a vector

Question 6

Bacterial Diseases

Answer 6

Salmonella causes food poisoning:
- symptoms = fever, stomach cramps, vomiting and diarrhoea
- prevention = vaccinating poultry, correctly preparing food and good hygiene
Gonorrhoea is a STD:
- symptoms = pain when urinating and thick yellow/green discharge from vagina or penis
- treatment = antibiotics
- prevention = using barrier contraception when having sex, e.g. condoms

Question 7

Viral Diseases

Answer 7

Measles is spread by droplets of liquid from sneezes/coughs:
- symptoms = red rash and fever
- prevention = vaccinations
HIV is a STD which attacks the cells in the immune system and develops into AIDS:
- symptoms = flu-like symptoms
- prevention = barrier contraception, not sharing needles
- treatment = antiviral drugs (NOT A CURE)
Tobacco mosaic virus affects plants and their ability to carry out photosynthesis:
- symptoms = discolouration on leaves, stunted growth
- prevention = removing infected plants

Question 8

Fungal Diseases

Answer 8

Rose black spot can be spread in the wind or water, and limits a plants ability to carry out photosynthesis:
- symptoms = black spots on leaves, stunted growth
- prevention = isolating infected plants and washing tools after using them on infected plants
- treatment = fungicides and removing infected leaves off the plant

Question 9

Protist Diseases

Answer 9

Malaria is a disease in which mosquitoes are the vectors. They become infected when they feed on an infested animal:
- symptoms = fever
- prevention = destroying mosquito habitats, vaccinations and mosquito nets

Question 10

Plant Deficiencies

Answer 10

Plants need ions from the soil. If there isn’t enough, the plants suffer from deficiency symptoms:
- Nitrates = stunted growth
- Magnesium = yellow leaves

Question 11

Plant Defences

Answer 11

Plants have physical, chemical and mechanical defences to stop pathogens:
- physical = waxy cuticle, cell walls, layer of dead cells
- chemical = antibacterial chemicals, poisons
- mechanical = thorns, hairs, leaves that droop or curl, mimicry

Question 12

Human Defence System

Answer 12

1) the skin acts as a barrier to pathogens
2) hairs and mucus in your nose trap particles
3) the trachea and bronchi secrete mucus to trap pathogens, they also have cilia which move back and forth to transport the mucus towards the throat, trapping any pathogens in the mucus which is usually swallowed
4) the stomach contains hydrochloric acid to kill any pathogens that enter the body via the mouth

Question 13

Immune System

Answer 13

Made up of two types of blood cells: lymphocytes and phagocytes.
- Lymphocytes produce antitoxins to neutralise toxins and also produce antibodies. Pathogens have antigens on their surface which these antibodies ‘lock’ onto and then the white blood cells can destroy the pathogens.
- Phagocytes carry out phagocytosis, which is when white blood cells engulf pathogens and digest them.

Question 14

Vaccinations

Answer 14

The injection of a dead or weakened version of a pathogen, triggering your body into producing antibodies which will attack the pathogen so if infected again, the whit blood cells can produce antibodies quickly.
Pros: helps control communicable diseases, helps prevent epidemics
Cons: aren’t always effective, some may have severe side effects to the vaccine

Question 15

Drugs

Answer 15

Painkillers - relive symptoms, but do not tackle the cause
Antibiotics - kill bacteria only

Question 16

Developing Drugs

Answer 16

Pre-clinical testing:
1) drugs are tested on human cells and tissues
2) testing carried out on living animals
Clinical testing:
3) tested on healthy human volunteers, starting on a low dose
4) tested on people with the illness, to find the optimum dose
Placebo - a substance that is like the drug, but doesn’t do anything
Placebo effect - when the patient thinks treatment will work even though their treatment isn’t doing anything
Blind trial - when the patient doesn’t know whether they’re getting the drug or placebo
Double-blind trial - when neither the doctor or patient know if they’re getting the drug

Question 17

Drugs from Plants

Answer 17

Chemicals produced by plants to defend themselves can be used to treat human diseases or relive symptoms, e.g:
- willow = aspirin
- foxglove = digitalis
- mould = penicillin

Question 18

Monoclonal Antibodies

Answer 18

1) mouse is injected with chosen antigen
2) immune cells are isolated/extracted
3) these B-lymphocytes are then fused with tumour cells
4) hybridoma cell is formed
5) it divides quickly to produce lots of clones, which produce the monoclonal antibodies
6) these can then be collected and purified

Question 19

Uses of Monoclonal Antibodies

Answer 19

Pregnancy testing: HCG hormone is found in the urine of pregnant women; pregnancy testing sticks detect this hormone and the HCG binds to the antibodies on the stick, triggering a colour change if you’re pregnant.
Treating disease: anti-cancer drugs can be attached to monoclonal antibodies and target specific cells by binding to the cancer marker. This kills the cancer cells but not the normal body cells.
Research to find specific substances: the antibodies bind to hormones and chemicals in the blood to measure levels and can be used in blood tests for pathogens and locating molecules on a cell or tissue

Question 20

Problems of Monoclonal Antibodies

Answer 20

They have more side effects than originally thought, e.g. fever, vomiting, low blood pressure, so are not used by doctors as much as was first thought