Edexcel GCSE Biology - Health, disease and the development of medicines

5.1 Describe health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, as defined by the World Health Organization (WHO)

Health is a state of complete physical, mental and social well-being.

5.2 Describe the difference between communicable and non-communicable diseases

Communicable are contagious.

Non-communicable diseases cannot be passed from person-to-person.

5.3 Explain why the presence of one disease can lead to a higher susceptibility to other diseases

A disease can damage the immune system or the body's natural defences/barriers, making easier for pathogens to enter the body.

A disease can cause organ systems to stop working well, making other (non-communicable) disease more likely.

5.4 Describe a pathogen as a disease-causing organism, including viruses, bacteria, fungi and protists

A pathogen is a disease-causing organism.
- Viruses
- Fungi
- Bacteria
- Protists

5.5 Describe some common infections, including:
a cholera (bacteria) causes diarrhoea

Cholera (bacteria) causes diarrhoea.
Spread by water

Prevention: Drinking safe, clean water

5.5 Describe some common infections, including:
b tuberculosis (bacteria) causes lung damage

Tuberculosis (bacteria) causes lung damage.
Spread airborne

Prevention: Avoiding close proximity with those it; vaccine

5.5 Describe some common infections, including:
c Chalara ash dieback (fungi) causes leaf loss and bark
lesions

Chalara ash dieback (bacteria) causes bark lesions and tree loss.
Spread airborne

5.5 Describe some common infections, including:
d malaria (protists) causes damage to blood and liver

Malaria (protists) causes blood and liver damage.
Spread by animal vectors

5.5 Describe some common infections, including:
e HIV (virus) destroys white blood cells, leading to the onset of AIDS

HIV (virus) destroys white blood cells, leading to the onset of AIDS.
Spread by bodily fluids

5.5 Describe some common infections, including:
f stomach ulcers caused by Helicobacter (bacteria)

Stomach ulcers caused by Heliobacter (bacteria).
Spread by oral transmission

5.5 Describe some common infections, including:
g Ebola (virus) causes haemorrhagic fever

Ebola (virus) causes haemorrhagic fever.
Spread by bodily fluids

5.7B Describe the lifecycle of a virus, including lytic pathways

1. Using host cell proteins and enzymes, the virus replicates its DNA and makes viral components.
2. Next, the viral components are assembled to form new virus particles.
3. Once the host cell is full of virus particles, it bursts in a process called lysis
4. The process is then repeated with nearby cells.

5.7B Describe the lifecycle of a virus, including lysogenic pathways

1. The virus uses restriction enzymes to insert its DNA into the host cell DNA.
2. The host cell replicates, and the viral DNA is also copied in this process.
3. The lytic cycle begins at this point, starting with the assembly of new
viral particles

5.8 Explain how sexually transmitted infections (STIs) are spread
and how this spread can be reduced or prevented, including:
a Chlamydia (bacteria)

Chlaymdia (bacteria) causes infertility.
Spread by bodily and sexual fluids

Prevention: contraception

5.8 Explain how sexually transmitted infections (STIs) are spread
and how this spread can be reduced or prevented, including:
b HIV (virus)

HIV (virus) kills white blood cells.
Spread by bodily and sexual fluids

Prevention: Contraception and not sharing injection equipment

5.9B Describe how some plants defend themselves against attack
from pests and pathogens by physical barriers, including the leaf cuticle

Plants have a waxy cuticle, a barrier stopping pathogens entering the plant.

Also stops water collecting on leaf, reducing infection of water-borne diseases.

5.9B Describe how some plants defend themselves against attack
from pests and pathogens by physical barriers, including cell wall

Plant cells are surrounded by a cell wall made from cellulose - a physical barrier against pathogens which entered the plant.

5.10B Describe how plants defend themselves against attack from pests and pathogens by producing chemicals, some of which
can be used to treat human diseases or relieve symptoms

Plants also produce chemicals which kill pathogens such as bacteria and fungi.

They can also stop herbivores from eating them.

5.10B Describe how plants defend themselves against attack from pests and pathogens by producing chemicals, some of which
can be used to treat human diseases or relieve symptoms

- Aspirin is made from a chemical found in bark and leaves of willow trees.
Relieves pain and fever

5.11B Describe different ways plant diseases can be detected and identified, in the lab and in the field including the elimination of possible environmental causes

Changing the environmental conditions (adding nutrients to soil) and observing change in plant symptoms can eliminate environmental factors (e.g nutrient deficiency)

5.11B Describe different ways plant diseases can be detected and identified, in the lab and in the field including the distribution analysis of affected plants

Looking at the pattern of damaged plants to find cause of damage.

- Flooding affects all plants.
- Wind-spread diseases affects a wide portion.
- Soil pathogens affect a small portion

5.11B Describe different ways plant diseases can be detected and identified, in the lab and in the field including the observation of visible symptoms

Looking for visible symptoms.

- Change in growth
- Change in colour
- Lesions on stems/leaves

5.11B Describe different ways plant diseases can be detected and identified, in the lab and in the field including the diagnostic testing to identify pathogens

Sending samples for testing and diagnosis.

- Technology to look at genetic material
- Growing pathogen from damaged crops
- Testing soil samples for nutrients and toxins

5.12 Describe how the physical barriers of the human body provide protection from pathogens, including:
a physical barriers, including mucus, cilia and skin

Mucus - in mouth and nose
Traps dust and pathogens

Cilla - lung airways
Carries dust and pathogens out of the body

Skin - thick barrier
Pathogens have difficulty getting past skin
- Can only enter body through wounds and cuts

5.12 Describe how the chemical defences of the human body provide protection from pathogens, including:
b chemical defence, including lysozymes and hydrochloric
acid

Lysozymes - in tears
- breaks down cell walls of bacteria - making pathogen inactive

Hydrochloric acid - secreted by cells lining stomach
- reducing pH of stomach to 2 - killing pathogen
(Helicobacter can survive this)

5.13 Explain the role of the specific immune system of the human body in defence against disease, including:
a exposure to pathogen
b the antigens trigger an immune response which causes the
production of antibodies
c the antigens also trigger production of memory
lymphocytes
d the role of memory lymphocytes in the secondary response to the antigen

1. Immune system uses antigens to identify pathogen in the body.
2. A lymphocyte without antibodies attach to pathogen.
3. The antigens trigger an immune response which produces antibodies
4. Lymphocyte stops pathogen from working
5. Lymphocyte is divided and spread around body

5.13 Explain the role of the specific immune system of the human body in defence against disease, including:
c the antigens also trigger production of memory
lymphocytes
d the role of memory lymphocytes in the secondary response to the antigen

1. Antigens trigger production of memory lymphocytes. They remain in the blood.
2. The memory lymphocytes causes a much faster secondary response, producing more antibodies.

5.14 Explain the body's response to immunisation using an inactive form of a pathogen

The body has a very little reaction to the inactive pathogen and the immune system produces memory lymphocytes.

5.15B Discuss the advantages of immunisation, including the concept of herd immunity

- Herd immunity prevents the pathogen spreading, even for those without immunity.
- Gives protection for many years
- Cheaper than treating ill person

5.15B Discuss the disadvantages of immunisation, including the concept of herd immunity

- Vaccine might not work (no immunity)
- Causes a bad reaction (high temperature and fits)

5.16 Explain that antibiotics can only be used to treat bacterial infections because they inhibit cell processes in the bacterium but not the host organism

Antibiotics only treat bacterial infections because they inhibit cell processes in the bacterium but not the host organism.

5.20 Describe that the process of developing new medicines, including antibiotics, has many stages, including discovery,
development, preclinical and clinical testing

DISCOVERY
DEVELOPMENT
Pre-clinical testing
- Testing on cells and tissues in lab
- Testing on a live animal

Clinical testing
- Testing on small amount of healthy people

Then needs to be approved by a medical agency.