Biology 2.8 Disease, Defence and Treatment

What is a pathogen?

A microorganism that causes disease

What is a non-pathogenic microorganism?

Any microorganism that does not cause
disease

Give an example of a non-pathogenic microorganism

Gut bacteria help to digest food
Skin flora help to prevent infection by competing with pathogens for resources

Give 4 types of pathogen

Bacteria
Viruses
Protists
Fungi

Give 5 features of bacteria cells

Cell membrane
Cell wall
Cytoplasm
Plasmid loops of DNA
No nucleus but large DNA loop instead

Describe the structure of a virus

They contain some genetic material
surrounded by a protein shell

Give 6 ways diseases can be spread

Droplet infection
Eating contaminated food
Drinking contaminated water
Direct contact
Vectors like insects
Contact with infected bodily fluids

What is the name of the pathogen that causes AIDS?

Human immunodeficiency virus (HIV)

What are the symptoms of AIDS

HIV weakens the immune system
Fever
Flu-like symptoms
Rash

How can the spread of HIV be prevented

HIV is spread through bodily fluids
Don’t share needles
Wear condoms during sex

What is the name of the pathogen that causes chlamydia?

Chlamydia trachomatis bacteria

What are the symptoms of chlamydia

Pain when urinating
Painful discharge from the penis or vagina
Bleeding between periods for women

How can the spread of chlamydia be prevented

Wear condoms during sex

What is the name of the pathogen that causes malaria?

Plasmodium falciparum

What are the symptoms of malaria

Fever
Vomiting and diarrhoea
Headaches
Muscle and or abdominal pain

How can the spread of malaria be prevented

Wearing long clothing
Wearing mosquito repellent
Sleeping with mosquito nets
Use malaria prevention tablets

Give 5 non-specific human defences to disease

The skin acts as a barrier
Stomach acid kills ingested pathogens
Mucus traps pathogens
Sweat contains antimicrobial chemicals
Blood clots prevent pathogen entry into wounds

Give 2 ways that lymphocytes can respond to detecting a pathogen

Produce antibodies that are specific to antigens and activate phagocytes
Produce antitoxins to neutralise toxins released by pathogens

How do phagocytes respond to detecting a pathogen

Phagocytes engulf and break down pathogens
in a process known as phagocytosis

What are antigens

Molecules on the surface of cells that are recognised by the immune system
and trigger an immune response

What do antibodies do

Bind to antigens and help the immune system
to neutralise infection

Give 2 types of pathogen that vaccines can protect against

Bacteria
Viruses

Why might parents choose to have their child vaccinated

Vaccines save lives and prevent disease
Treatment may be unaffordable in countries without free healthcare

Why might parents choose not to have their child vaccinated

Concern about side effects
Unaware of vaccine contents
Religious or cultural objections
Belief vaccines are linked to other diseases

What negative impacts could arise from not vaccinating children

Can lead to disease outbreaks
Epidemics or pandemics
Strain on healthcare systems

How do vaccines work (Higher)

Dead or inactive pathogens or antigens are injected
Lymphocytes produce antibodies
Memory cells are created for long term immunity

Why is the secondary immune response faster than the primary response (Higher)

Memory cells remain in the blood
They produce antibodies much more quickly

What type of pathogen do antibiotics kill

Bacteria

What was the first ever antibiotic discovered

Penicillin discovered by Alexander Fleming in 1928

Outline how antibiotics work

Stop bacteria from growing or kill them
without damaging host cells

What type of microorganism produces penicillin

A fungus called penicillium

What is semisynthetic penicillin

Penicillin that has been modified chemically

What is synthetic penicillin

Penicillin produced chemically from scratch

Give one example of an antibiotic resistant bacterium

MRSA
Methicillin resistant Staphylococcus aureus

State 3 ways of controlling the spread of MRSA

Cover wounds with sterile dressings
Wash hands surfaces and equipment thoroughly
Treatment and screening programmes

Give 3 ways diseases can be prevented

Washing hands
Balanced and healthy diet
Drinking clean water

What are the stages in the development of new medicines

Research and testing on lab grown cells
Animal testing
Testing on healthy volunteers
Testing on people with the disease

What are preclinical trials

Testing drugs on lab grown cells and tissues
Using computer modelling to understand effects

What is a placebo

A substance that looks like the drug
but has no effect

What are placebos used for

To test the effectiveness of a new drug
by providing a comparison

What is a blind trial

Patients do not know which drug is real
and which is the placebo

What is a double blind trial

Neither patients nor researchers know
which drug is real or placebo to avoid bias

How do lymphocytes produce monoclonal antibodies (Higher)

Lymphocytes are activated by antigens
They divide to produce large quantities of identical antibodies

How are monoclonal antibodies produced in a lab (Higher)

Antigens injected into a mouse
Mouse produces lymphocytes
Lymphocytes fused with myeloma cells
Hybridoma produces antibodies rapidly

How can monoclonal antibodies be used to detect diseases (Higher)

Monoclonal antibodies attached to fluorescent dyes
They fluoresce if the pathogen is present

How are monoclonal antibodies used in tissue and organ transplants (Higher)

Used to deactivate T cells
so there is no immune response

How are monoclonal antibodies used to help chemotherapy (Higher)

They target cancer cells
and deliver drugs directly to them