3. GCSE Biology - Infection and response

What is health?

Health is the state of physical and mental well-being.

What is a pathogen?

A microorganism that causes infectious disease

Pathogens can cause communicable diseases, what is a communicable disease?

Communicable - An infectious disease

List 4 different types of pathogens.

1. Virus

2. Bacteria

3. Bacteria

4. Protists

Give 3 examples of viruses.

1. Measles

2. Rubella

3. HIV

Give an example of a disease caused by a Fungi?

Athlete's foot

Give an example of bacteria and what does bacteria look like (picture in head)?

food poisoning (salmonella)

General info about bacteria (3)

1. very small

2. living single-celled organisms

3. the majority are harmless and even useful to us (e.g. in yoghurt) but some are pathogenic

Give an example of protist?

The pathogen that causes malaria

How do bacteria make us ill?

1. Divide rapidly

2. May produce toxins that damage your tissues and affect body functions

3. May damage cells directly

General info about viruses (3)

1. non-living microbes that need host cells to reproduce and survive

2. extremely small (much smaller than bacteria)

3. cause disease in every type of organism

List the way diseases can spread, giver further examples of these ways.

• Air; Colds, TB

• Contaminated water; Cholera

• Body fluid; AIDS, Chicken Pox, Cholera

• Mother to unborn baby; Rubella

• Vector; Insects or rats

• Direct contact; Chicken pox, Athlete's foot, Rubella

• Cuts/Sharing needles; AIDS, Tetanus

• Contaminated food; food poisoning

• Contaminated blood; AIDS

How do viruses make us ill?

1. take over cells in the body

2. live and reproduce inside cells, damaging them and destroying them

List 3 facts about protists

1. all Eukaryotes

2. majority are single-celled

3. often transferred by vector

How can we reduce the spread of diseases? (4)

1. Simple hygiene measures; handwashing, tissues

2. Destroying vectors; pesticides, fuming mosquitos

3. Isolation of infected individuals

4. Vaccination

How are pathogens spread? Give examples (3)

1. By air - droplet infection

2. Direct contact

3. By water

How are pathogens spread by direct contact? (4) Give examples for each

1. Animals act as vectors between infected and non-infected individual e.g. malaria

2. STIs via direct skin contact and bodily fluids e.g. syphilis

3. Pathogens enter body via cuts or needle punctures e.g. HIV

4. In plants where infected material infects new crop e.g. TMV

How are pathogens spread by air? Give 2 examples

Droplets with pathogen released when person coughs or sneezes and another person breathes them in. e.g. coughs & colds, athlete's foot

How are pathogens spread by water?

Pathogens enter digestive system by:

1. Drinking water containing sewage e.g. cholera

2. Eating raw, undercooked or contaminated food e.g. salmonella

Measles: symptoms, transmission, prevention and treatment

1. Symptoms: fever, red skin rash

2. Transmission: droplets through sneezes and coughs

3. Prevention: vaccination

4. Treatment: no treatment

HIV: symptoms

• initially flu-like illness

• unless controlled virus attacks immune cells

• late stage HIV/AIDS when immune system so badly damaged it cannot deal with other infections/cancers

HIV: transmission

• sexual contact

• exchange of bodily fluids e.g. sharing needles

HIV: Prevention

• contraception

• no sex

HIV: treatment

• antiretroviral drugs

Salmonella: symptoms

• fever

• abdominal cramps

• vomiting

• diarrhoea

Salmonella: Transmission

• bacteria ingested in food/on food prepared in unhygienic conditions

Salmonella: Prevention

• poultry vaccinated against Salmonella

Salmonella: Treatment

• drink lots of fluids

• stay comfortable

• antibiotics (if serious)

Gonorrhoea: symptoms

• thick yellow/green discharge from vagina/penis

• pain on urinating

Gonorrhoea: Transmission

• STI; sexual contact

Gonorrhoea: Prevention

• barrier method of contraception

Gonorrhoea: Treatment

• antibiotics

• treated easily with antiobiotic penicillin until resistant strains appeared

Malaria: how it works

• caused by protists

• malarial protist has a life cycle that includes the mosquito

• affects the liver and damages red blood cells

Malaria: Symptoms

• recurrent episodes of fever

• shaking when protists burst out of red blood cells

• can be fatal

Malaria: Transmission

• vector; mosquito

Malaria: Prevention

• mosquito nets

• preventing vectors from breeding

Malaria: Treatment

• antimalarial medicine

what do vaccines contain?

• inactive pathogens

OR

• live but weakened pathogens

Name and describe the non-specific defence systems of the human body (4)

1. skin - physical barrier, waterproof, anti-microbial secretions, microorganisms living on it outcompete pathogens

2. nose - mucus + nasal hairs trap pathogens

3. trachea + bronchi - mucus and cilia waft mucus to back of throat where it can be swallowed

4. stomach - hydrochloric acid to kill pathogens

How do white blood cells help defend against pathogens? (3)

1. phagocytosis

2. antibody production

3. antitoxin production

What is a lymphocyte?

a white blood cell

What is phagocytosis?

White blood cells called phagocytes engulf foreign cells (pathogen) and digest them

phagocyte

a type of white blood cells that engulfs a pathogen and breaks it down

What is an antigen?

proteins produced by pathogens that are foreign to the body

antibodies are specific to the…

antigen

How does vaccination work? (3)

1. small quantities of dead/inactive forms of a pathogen introduced into body

2. this stimulates white blood cells to produce antibodies

3. if the same pathogen re-enters the body, memory cells response quickly to produce the correct antibodies

what is herd immunity?

when a large population is immune to the disease, the spread of the pathogen is reduced a lot and the disease may disappear

Pencillin: taken as, role, cons

1. taken as pill, syrup, or injected

2. role: cures bacterial diseases by killing infective bacteria inside the body, however specific bacteria should be treated by specific antibodies

3. cons: strains of resistant bacteria emerging, cannot be used to kill viruses as these live inside cells

Why is it difficult to develop drugs that kill viruses?

Viruses are inside cells so it is difficult to develop drugs that won't damage the body's tissues

What are painkillers used for?

Treating the symptoms of disease, however they do not kill pathogens

Traditionally where do we drugs extracted from?

Plants and microorganisms

Give 3 examples of drug discoveries

1. heart drug digitalis originates from foxglove

2. painkiller aspirin originates from willow

3. penicillin was discovered by Alexander Fleming from the Penicillum mould

How are most new drugs created?

Synthesised by chemists in a pharmaceutical industry - however starting point may still be a chemical extract from a plant

define antiseptic

chemical that kills microorganisms in the environment and safe for the skin

antibiotic

drugs that can kill bacteria (not viruses) inside the body

How does antibiotic resistance develop? (4)

1. bacteria shows lots of variation due to mutations which produce new strains

2. antibiotics kill bacteria which are non-resistant

3. bacteria that are resistant survive and reproduce

4. population of resistant bacteria increases because people are not immune and there is no effective treatment

Why must new medical drugs be tested and trialled?

To ensure they are safe and effective

What are new drugs tested for? (3)

1. toxicity (is it toxic?)

2. efficacy (does it do its job?)

3. dose (what quantity should be used on each patient?)

What are the 4 overall stages of drug development?

1. Laboratory

2. Preclinical trials

3. Clinical trials

4. Peer review

What is preclinical testing?

Testing done in a laboratory using cells, tissues and live animals

What are clinical trials, and what are the 3 stages?

Clinical trials use healthy volunteers and patients

1. at the start very low doses of drug are given

2. if the drug is safe, further trials including on those suffering from the disease are carried out to find the optimum dose

3. in double blind trials, some patients are given a placebo

What is a placebo drug?

A drug that does not contain the medicine being investigated (may contain no medicine at all)

Describe a double blind trial (4)

1. patients randomly split into 2 groups

2. 1 group given drug being tested, 1 given placebo

3. neither doctors nor patient know which has which to guard against bias

4. health of patients is carefully monitored during trial

Monoclonal antibodies

See this separate quizlet set: quizlet.com/240906580/gcse-aqa-biology-cell-division-monoclonal-antibodies-flash-cards/

How can plant diseases be detected? (7)

1. stunted growth

2. areas of decay (rot)

3. spots on leaves

4. growths

5. malformed stems or leaves

6. discolouration

7. presence of pests

How can you identify a plant disease?

1. reference to a gardening manual or website

2. take infected plants to laboratory to identify pathogen

3. use testing kits that contain monoclonal antibodies

Tobacco Mosaic Virus (TMV)

1. viral disease

2. which damages leaves by leaving them with a 'mosaic' pattern of discolouration

3. damaged parts cannot photosynthesise

Black spot disease

1. fungal disease

2. dark purple/black spots on leaves, lesions on stem

3. infected leaf may yellow and fall off, limiting photosynthesis

Aphid damage

1. caused by insect plant pests aphids

2. suck phloem sap out of phloem vessels

3. cause stunted growth, may transmit other diseases, some secrete a honeydew which allows black moulds to grow on plant

Describe 2 ion deficiency conditions

1. stunted growth - caused by nitrate deficiency

2. chlorosis - caused by magnesium deficiency

What are the nitrate ions and magnesium ions needed for in plants?

1. nitrate ions - protein synthesis

2. magnesium ions - to make chlorophyll

Physical defence responses of plants (3)

1. cellulose cell walls

2. tough waxy cuticle on leaves

3. layers of dead cells around stem (bark on trees) which fall off

Chemical plant defence responses (2)

1. antibacterial chemicals

2. poisons to deter herbivores

Mechanical adaptations of plants (3)

1. thorns and hairs deter animals

2. leaves which droops or curl when touched

3. mimicry to trick animals