Biology AQA-3.Infection and Response

How do diseases caused by viruses spread?

airborne droplets, direct contact, or contaminated surfaces

How do diseases caused by bacteria spread?

contaminated food/water, air, or direct contact

How do diseases caused by protists spread?

vectors

How do diseases caused by Fungi spread?

airborne spores or direct contact

Pathogens

microorganisms that cause infectious disease

Name 4 pathogens

viruses, bacteria, protists and fungi

What may reproduce rapidly inside the body?

Bacteria and viruses

Bacteria may produce…

poisons that damage tissues and make us feel ill.

Viruses live and reproduce inside…

cells, causing cell damage

Measles is a…

viral disease that can be fatal if complications arise

What are the symptoms of measles?

fever and a red skin rash

What are the prevention of measles?

Most young children are vaccinated

What are the transmission of measles?

inhalation of droplets from sneezes and coughs

What are the symptoms of HIV?

Early symptoms: Flu-like illness

If untreated: HIV attacks the immune system

Late stage: AIDS develops when the immune system is severely damaged and can’t fight other infections or cancers

What is the treatment of HIV?

antiretroviral drugs to prevent progression to AIDS

What are the transmission of HIV?

sexual contact or exchange of body fluids

Tobacco mosaic virus (TMV) is a…

widespread plant pathogen affecting many species of plants

What are the effects of Tobacco Mosaic Virus (TMV) on plants?

a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis.

Salmonella food poisoning is spread by…

bacteria ingested in food, or on food prepared in unhygienic conditions.

In the UK, ????? are vaccinated against salmonella to control the spread.

poultry

Salmonella symptoms

Fever, abdominal cramps, vomiting and diarrhoea

Gonorrhoea is a…

sexually transmitted disease (STD) caused by a bacterium

Gonorrhoea symptoms

thick yellow or green discharge from the vagina or penis and pain on urinating

What was Gonorrhoea easily treated with and why did it stop working?

the antibiotic penicillin until many resistant strains appeared.

Gonorrhoea is spread by sexual contact. The spread can be controlled by…

treatment with antibiotics or the use of a barrier method of contraception

Rose black spot is a…

fungal disease

Rose black spot Symptoms

purple or black spots develop on leaves, which often turn yellow and drop early affecting the growth of the plant as photosynthesis is reduced

Rose black spot can be treated by using…

fungicides or removing and destroying the affected leaves.

Rose black spot is spread in the environment by…

water or wind

The pathogens that cause malaria are…

protists

The malarial protist has a life cycle that includes the…

mosquito

What are the symptoms of malaria?

recurrent episodes of fever and can be fatal

What is the prevention of malaria?

preventing the vectors, mosquitos, from breeding and by using mosquito nets to avoid being bitten

vector

an organism or a molecule that acts as a carrier, transferring genetic material or pathogens from one place to another

describe the non-specific defence system:

Skin

physical barrier, produces antimicrobial secretions which kill pathogens

describe the non-specific defence system:

Nose

Hairs and mucus trap pathogens

describe the non-specific defence system:

Trachea and bronchi

Lined with cilia and mucus to trap and move pathogens out of the airways

describe the non-specific defence system:

Stomach

Produces hydrochloric acid, which kills most ingested pathogens

What is the role of the immune system in defending against disease?

If a pathogen enters the body the immune system tries to destroy the pathogen.

White blood cells help to defend against pathogens by:

• Phagocytosis: Engulfing and digesting pathogens

• Antibody production: Target specific pathogens by attaching to antigens

• Antitoxin production: Neutralise the toxins released by bacteria

vaccination will prevent…

illness in an individual

the spread of pathogens can be reduced by…

immunising a large proportion of the population.

Vaccination involves…

introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies

Antibiotics, such as penicillin, are medicines that…

help to cure bacterial disease by killing infective bacteria inside the body

Antibiotics cannot kill…

viral pathogens

Painkillers and other medicines are used to treat…

symptoms of disease but do not kill pathogens

It is difficult to develop drugs that kill…

viruses without damaging the body’s tissues.

Traditionally drugs were extracted from…

plants and microorganisms

The heart drug digitalis originates from…

foxgloves

The painkiller aspirin originates from…

willow

Penicillin was discovered by…

Alexander Fleming from the Penicillium mould.

New medical drugs have to be…

tested and trialled

New drugs are extensively tested for…

toxicity, efficacy and dose

Preclinical testing is done in a…

laboratory using cells, tissues and live animals.

Clinical trials use…

healthy volunteers and patients.

In double blind trials, some patients are given a…

placebo

Monoclonal antibodies are produced from a…

single clone of cells

How are monoclonal antibodies produced?

• Stimulate mouse lymphocytes to produce a specific antibody

• Combine the lymphocytes with tumour cells to form hybridoma cells

• Hybridoma cells can divide and produce the antibody

• Single hybridoma cells are cloned to produce many identical cells that all make the same antibody

• Purify and collect large amounts of the monoclonal antibody

ways in which monoclonal antibodies can be used:

For diagnosis such as in…

pregnancy tests.

ways in which monoclonal antibodies can be used:

In laboratories to measure…

levels of hormones and other chemicals in blood, or to detect pathogens.

ways in which monoclonal antibodies can be used:

In research to locate or identify…

specific molecules in a cell or tissue by binding to them with a fluorescent dye

ways in which monoclonal antibodies can be used:

To treat some diseases: for cancer the monoclonal antibody can be bound to a…

radioactive substance, a toxic drug or a chemical which stops cells growing and dividing

Plant diseases can be detected by: (7 ways)

• stunted growth

• spots on leaves

• areas of decay (rot)

• growths

• malformed stems or leaves

• discolouration

• the presence of pests.

Identification for plant diseases can be made by: (3 ways)

• reference to a gardening manual or website

• taking infected plants to a laboratory to identify the pathogen

• using testing kits that contain monoclonal antibodies.

Plants can be infected by…

viral, bacterial and fungal pathogens as well as by insects.

Plants can be damaged by a range of ion deficiency conditions:

• stunted growth caused by nitrate deficiency

• chlorosis caused by magnesium deficiency.

Physical defence responses to resist invasion of microorganisms.

• Cellulose cell walls.

• Tough waxy cuticle on leaves.

• Layers of dead cells around stems (bark on trees) which fall off.

Chemical plant defence responses.

• Antibacterial chemicals.

• Poisons to deter herbivores.

Mechanical adaptations.

• Thorns and hairs deter animals.

• Leaves which droop or curl when touched.

• Mimicry to trick animals.