GCSE AQA Biology - Infection and response

Pathogens

Microorganisms that enter the body and cause disease

4 Pathogens

Bacteria, viruses, protists and fungi

Communicable diseases

Diseases that can easily be spread

How do bacteria make you feel ill?

By producing toxins that damage your cells and tissues.

How do viruses make you feel ill?

By replicating themselves inside of your cells until the cell bursts, causing damage the cell.

What are the three ways pathogens can be spread?

• Water

• Air

• Direct contact

Three viral diseases

• Measles

• HIV

• TMV (Tobacco mosaic virus)

How is measles spread?

By inhalation of droplets from an infected person’s sneeze or cough

What are the symptoms of measles?

A red skin rash, a fever and even fatal complications.

How do we protect against measles?

By vaccinating people from a young age.

How is HIV spread?

By sexual contact or exchanging bodily fluids (blood when sharing needles)

What are the initial symptoms of HIV?

Flu-like symptoms.

What does HIV do to the body?

It attacks the body’s immune cells.

How can we control HIV from attacking immune cells?

By using antiretroviral drugs.

What is AIDS?

The late stage of HIV infection, in which the body’s immune system becomes so badly damaged it cannot deal with other infections or cancers.

What does TMV affect?

Many species of plants including tomatoes.

What is the symptom of TMV?

A ‘mosaic’ pattern of discolouration on the leaf, showing it can’t photosynthesise as well and grow properly.

What is an example of a fungal disease?

Rose black spot

What are the symptoms of rose black spot?

Leaves develop purple or black spots, turn yellow and drop off early.

What is the effect of rose black spot?

Causes the rate of photosynthesis to fall and reduces the rate of growth.

How is rose black spot spread?

By water or by wind.

How can gardeners treat rose black spot?

By using fungicides and removing and destroying the affected leaves.

What disease is caused by a protist?

Malaria

How are malarial protists spread?

By mosquitos (vectors) picking up the protist when they feed on infected animals, and inserting the protist into other animals when they feed on them.

How can we control the spread of malaria?

• Preventing vectors from breeding

• Using insecticides and mosquito nets

What are two bacterial diseases?

• Salmonella

• Gonorrhoea

What are the 4 symptoms of salmonella?

Fever, stomach cramps, vomiting and diarrhoea

How is salmonella spread?

By food poisoning from eating food that’s been contaminated with salmonella bacteria.

How can we control spread of salmonella?

• Vaccinating poultry against salmonella

• Prepare food in hygienic conditions

How is Gonorrhoea spread?

By unprotected sexual contact

What are the symptoms of gonorrhoea?

Pain when urinating and a thick yellow discharge from the vagina or the penis.

How can we prevent the spread of gonorrhoea?

• Treating people with antibiotics

• Using barrier methods of contraception

What are the 4 ways we can reduce and prevent the spread of disease?

• Being hygienic

• Destroying vectors

• Isolating infected individuals

• Vaccination

What are 4 non-specific defense systems of the human body?

• Skin

• Nose

• Trachea and bronchi

• stomach

How does the skin defend against infection?

It acts as a physical barrier to pathogens and secretes antimicrobial substances which kill pathogens.

How does the nose defend against infection?

Hairs and mucus in the nose trap pathogens before they can reach the lungs.

How do the trachea and bronchi defend against infection?

They secrete mucus to trap pathogens, and cilia waft pathogens and mucus upwards.

How does the stomach defend against infection?

It produces hydrochloric acid to kill any pathogens.

What are the 3 functions of white blood cells?

• Consume pathogens (phagocytosis)

• Produce antibodies

• Produce antitoxins

Phagocytosis

White blood cells engulf foreign cells and digest them.

Antigens

Unique molecules on the surface of cells or pathogens.

What will some types of white blood cells do when they come across a foreign antigen?

They will produce antibodies specific to the antigen which lock onto the antigen of the invading pathogen so they can be found and destroyed by other white blood cells.

How do some white blood cells counteract toxins?

By producing antitoxins

How do vaccines work?

• The body produces antibodies to respond to antigens on small amount of dead or inactive pathogens.

• This means that if the same type of pathogen reappears, the white blood cells can quickly produce antibodies to respond to it.

Advantages of vaccines

Control communicable diseases and prevent large outbreaks

How does herd immunity protect unvaccinated individuals?

The spread of the disease is significantly reduced when most people are vaccinated, making it harder for the pathogen to infect unvaccinated individuals.

Disadvantages of vaccines

They don’t always work, and you can sometimes have a bad reaction.

Painkillers

Relieve pain and reduce symptoms, but don’t actually kill pathogens.

Antibiotics

Kill bacteria

How can bacteria become resistant to antibiotics?

If not all bacteria are killed by antibiotics, some can survive and randomly mutate to subsequently produce resistant strains

What are the 3 reasons antibiotics are becoming