Infection and response (1)

Question 1

Virus-
Bacteria-
Fungi-
Protists-

How are they spread?

Answer 1

Virus- small microorganism (not a cell) that invades cells and rapidly reproduces, causing the cell to burst

Bacteria- small cells that release harmful toxins that cause pain

Fungi- small cells that grow and penetrate the skin, causing disease, and producing spores

Protists- carried by vectors and cause disease

-Air, water, direct contact

Question 2

Examples of Viruses (3)

Answer 2

Measles- spread by droplets of infected mucus, causes a red rash and disease
HIV- spread by unprotected sex, attacks white blood cells
TMV- causes a mottled effect on leaves

Question 3

Examples of Bacterial Infections-

Answer 3

Salmonella- caused by contaminated poultry, causes food poisoning
Gonorrhoea- spread by sexual contact, causes pain while urinating and thick, coloured discharge

Question 4

Example of fungal and protist spread disease-

Answer 4

fungal- rose black spot causes spots on leaves and limits photosynthesis

Malaria- spread by mosquitos, causes a deadly fever

Question 5

What does a lack of magnesium and nitrates do to a plant-

signs of plant disease-

Answer 5

magnesium- makes chlorophyll for photosynthesis. A lack of it causes yellowed leaves
Nitrates- make proteins for plant growth

Stunted growth, spots on leaves, rotting, discolouration

Question 6

Plant defences:
Physical-
Chemical-
Mechanical-

Answer 6

Physical- waxy cuticle and layer of dead cells (eg tree bark) prevents pathogens from entering the plant

Chemical- some plants produce toxins to kill pathogens that come into contact with them

Mechanical- Features like thorns to deter predators
Mimicry to deter predation

Question 7

Skin-
Hairs and mucus-
Trachea and bronchi-
Stomach-
White blood cells-

Answer 7

Skin- acts as a barrier against pathogens entering the body, and excretes an antimicrobial substance

Hairs and mucus- trap inhaled pathogens in the nose

The trachea and bronchi- secrete mucus and are lined with cilia which are hair-like structures that move mucus to the back of the throat so it can be swallowed

Stomach- produces hydrochloric acid that kills pathogens

White blood cells- Lymphocytes create antibodies
Phagocytes engulf and destroy the pathogen

Question 8

Natural drugs (3)-

Answer 8

Aspirin- a painkiller found in willow branches
Digitalis- a drug that treats heart conditions, found in foxgloves
Penicillin- a mould with antibiotic properties

Question 9

Painkillers-
Antibiotics-
Vaccines-

Answer 9

Painkillers- block the brain’s ability to register pain

Antibiotics- kill bacteria (however bacteria can mutate and become resistant)

Vaccines- a weakened pathogen injected into the bloodstream, so lymphocytes can develop antibodies to fight it without the risk of the person becoming ill
White blood cells remember how to create antibodies for the future
If you contract the real disease, the white blood cells can rapidly produce antibodies to neutralise it and prevent the person from becoming ill

Question 10

How are monoclonal antibodies produced?
What are their uses?

Answer 10

1. mouse injected with the target antigen
2. B-lymphocyte cell removed from mouse
3. B-lymphocyte fused with rapidly dividing tumour cell to create a hybridoma
4. The hybridoma rapidly divides to form many clones of the white blood cell that produce the desired antibody

Uses- drug tests for sports, pregnancy tests, curing disease

Question 11

Stages of drug development

Answer 11

1. preclinical testing on human cells and tissues
2. tests on live animals
3. clinical trials - tests on healthy humans with a low dosage
   Test on ill people to find optimal dosage
   Implement a placebo drug to ensure patients’ feedback is legitimate
   Tests are double blind so the patient and doctor don’t know if they have the drug or not to remove biased data
4. results aren’t published until they’re verified by other scientists