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Flashcards in SB5 Deck (56)
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What is health?

A state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.


What are the two types of disease?



What are communicable diseases?

Diseases that can be spread between individuals.


What are non-communicable diseases?

Diseases that can t be transmitted between individuals

E.g - cancer and heart disease.


What are pathogens?

Organisms such as viruses, bacteria, fungi and protists that cause communicable diseases.


What do viruses have to do to reproduce?

They have to infect living cells - host cells.

Specific types of viruses will only infect specific cells.


What happens at the start of the life cycle of a virus?

It starts when it infects a new host cell.

Many will then reproduce by the lytic pathway, but some can enter the lysogenic pathway first.


What is the lytic pathway?

1. The virus attaches itself to a specific host cell and injects its genetic material into the cell.
2. The virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses.

3. The viral components assemble.

4. The host cell splits open, releasing the new viruses, which infect more cells.


What is the lysogenic pathway?

1. The injected genetic material is incorporated into the genome (DNA) of the host cell.

2. The viral genetic material gets replicated along with the host DNA every time the host cell divides - but the virus is dormant and no new viruses are made.

3. Eventually a trigger (e.g - a chemical) causes the viral genetic material to leave the genome and enter the lytic pathway.


What is chlamydia?

1. Its a kind of bacterium, but it behaves in a similar way to a virus because it can only reproduce inside host cells.

2. Although it’s doesn’t always cause symptoms it can result in infertility.


How can the spread chlamydia be reduced?

Screening individuals
Avoiding sexual intercourse


What is HIV?

Human Immunodeficiency virus.
It kills white blood cells, which are important to the immune response.

It can eventually lead to AIDS (Acquired Immune Deficiency Syndrome).


What happens when a person gets AID?

The infected persons immune system deteriorates and eventually fails, because of this, the person becomes very vulnerable to infections by other pathogens.


How do you prevent the spread of HIV?

It’s spread through bodily fluids.

One of the main ways is to use a condom.
Drug users should avoid sharing needles.
Medication can reduce the risk of an infected individual passing the virus on to others during sex. (Or a mother to her baby during pregnancy).


What are the physical defences plants have against pathogens and pests?

Most leaves and stems have a waxy cuticle, which provide a barrier to stop pathogens entering them or pests form damaging them. It may also stop water collecting on the leaf, which could reduce the risk o infection by pathogens that are transferred between plants in water.

Plant cells themselves are surrounded by cell walls made form cellulose. These form a physical barrier against pathogens that make it past the way cuticle.


What are the chemical defences plants have against pathogens and pests?

For example antiseptics, which kill bacterial and fungal pathogens.
They also produce chemicals to deter pests from feeding on their leaves.

Some of the chemicals can be used as drugs to treat humans.


What are some example of plant chemicals being used in medicine?

Quinine comes from the bark of the cinchona tree. For years it was the main treatment for malaria.

Aspirin is used to relieve pain and fever. It was developed from a chemical ground in the bark and leaves of willow trees.


What are some physical barriers on humans that try to stop pathogens entering the body?

1. The skin - if it gets damaged, blood clots quickly seal cuts to keep microorganisms out.

2. Hair and mucus in your nose trap particles that could contain pathogens.


What are some chemical barriers in humans that try to stop pathogens entering the body?

The stomach produces hydrochloric acid. This kills most pathogens that are swallowed.

The eyes produce a chemical called lysozyme (in tears) which kills bacteria on the surface of the eye.


What happens if a pathogen gets into your body?

Your immune system kicks in to destroy them.

The most important part is the white blood cells.


What are B-lymphocytes?

A type of white blood cell that are involved in the specific immune response


How do B-lymphocytes work?

1. Every pathogen has unique molecules (proteins) on its surface called antigens.

2. When your B-lymphocytes come across an antigen on a pathogen, they start to produce proteins called antibodies.
Antibodies bind to the new invading pathogen, so it can be found and destroyed by other white blood cells.
The antibodies produced are specific to that pathogen.

3. The antibodies are then produced rapidly and flow all round the body to find all similar pathogens.


What do memory lymphocytes do?

Give immunity to later infection.


What does immunisation do?

Stops you getting infections.


How does immunisation work?

Usually involves injecting dead or inactive pathogens into the body.

These are antigenic (they carry antigens), so even though they’re harmless your body makes antibodies to help destroy them.

The antigens also trigger memory lymphocytes to be made.


What are the pros of immunisation?

1. Big outbreaks of diseases, called epidemics, can be prevented if a large percentage of the population are immunised.

2. Some diseases, e.g- smallpox, have been virtually wipe out by immunisation programmes.


What are the cons of immunisation?

1. Doesn’t always work - sometimes it doesn’t give you immunity.

2. You can sometimes have a bad reaction to a vaccine (e.g - swelling, or maybe something more serious like a fever or seizures). But bad reactions are rare.


What are monoclonal antibodies?

Identical antibodies.


How are monoclonal antibodies produced?

They’re produced from lots of clones of a single B-lymphocyte. This means all the antibodies are identical and will only target one specific protein antigen.


Why can you make monoclonal antibodies that target cancer cells?

Cancer cells have proteins on their cell membranes that aren’t found on normal body cells. They’re called tumour markers.

In the lab, you can make monoclonal antibodies that will bind to these tumour markers. They can be used to help diagnose and treat cancer.