Health And Disease

Question 1

Define health

Answer 1

A state of complete physical, mental and social well-being

Question 2

Define disease

Answer 2

A disorder of the body or mind that negatively affects an individual’s health

Question 3

What are the two types of disease?

Answer 3

• Communicable
• Non-communicable

Question 4

Define pathogen

Answer 4

A disease-causing organism e.g. virus, fungi, bacteria, protists

Question 5

What is a symptom?

Answer 5

A change experienced by an organism that indicates disease

Question 6

Why does having an illness make an individual more likely to contract another disease?

Answer 6

A disease may weaken an individual’s immune system making them increasingly susceptible to other infections.

Question 7

Describe cholera

Answer 7

• Caused by Vibrio cholerae bacterium
• Spread by drinking water or washing in water that has been contaminated with infectious faeces
• Symptoms: diarrhoea, vomiting

Question 8

Describe tuberculosis (TB)

Answer 8

• Caused by Mycobacterium tuberculosis bacterium
• It is an airborne bacteria spread by droplet infection
• Symptoms: lung damage, chesty cough, wheezing

Question 9

Describe malaria

Answer 9

• Caused by plasmodium protist
• Spread by mosquito vectors which pick up the plasmodium protist when feeding on the blood of an infected organism and transmit malaria to other organisms during feeding
• Flu-like symptoms, damage to red blood cells, liver damage

Question 10

Describe Ebola

Answer 10

• Caused by Ebola virus
• Spread by direct contact with infected body fluids e.g. blood, semen, saliva, mucus, vomit
• Symptoms: fever, diarrhoea, vomiting, internal bleeding

Question 11

Describe simply how viruses cause disease

Answer 11

They enter host cells and replicate inside of them. The host cells rupture, releasing new viruses.

Question 12

By what two pathways do viruses replicate inside living cells?

Answer 12

• Lytic pathway
• Lysogenic pathway

Question 13

Describe the lytic pathway

Answer 13

1. Virus binds to specific receptors on host cell
2. Virus injects its DNA into host cell and replicates its DNA
   using host cell machinery
3. New viral structures are produced and assembled
4. Host cell ruptures, releasing new viruses

Question 14

Describe the lysogenic pathway

Answer 14

1. Virus binds to specific receptors on host cell
2. Viral DNA injected into host cell and becomes integrated into host cell genome
3. Viral DNA replicates each time the host cell divides. However, the cell remains normal.
4. Trigger causes the activation of viral DNA. It enters lytic pathway.

Question 15

Describe the physical defence system within plants

Answer 15

• Waterproof waxy cuticle - surface barrier preventing the entry of pathogens
• Cellulose cell wall - further barrier against pathogens

Question 16

Give some examples of chemical barriers in plants

Answer 16

• Secretion of toxins to reduce damage by pests e.g. stinging nettles
• Production of antibacterial chemicals that kill bacterial pathogens

Question 17

Why are chemicals produced by plants useful?

Answer 17

They produce physiological effects on the body so can be used in medicines to treat disease.

Question 18

Give an example of a medicine derived from plants

Answer 18

• Quinine - antimalarial, bark of Cinchona sp.
• Aspirin - painkiller, bark/leaves of Salix alba

Question 19

Why are plant defence systems important?

Answer 19

• Plants are producers so all organisms higher up in food chains rely upon their survival and ability to fight disease
• Important in maintaining human food security

Question 20

How can plant diseases be detected and identified in the field?

Answer 20

• Observation of symptoms e.g. Chalara ash dieback disease causes bark lesions. Books and online resources aid identification
• Analysis of the distribution of infected plants can indicate the type of pathogen involved and its mode of transmission e.g. airborne
• Changing environmental conditions to eliminate other causes such as nutrient deficiencies or water-logged soils

Question 21

Give some examples of the body’s physical defence system

Answer 21

• Skin - protective surface barrier
• Blood clotting - platelets seal wounds preventing entry of pathogens into the blood
• Respiratory tract - mucus traps pathogens, cilia waft mucus to the back of the throat where it is swallowed

Question 22

Give some examples of the body’s chemical defence system

Answer 22

• Tears - contain lysozyme which digests bacterial cell walls, killing bacteria and protecting the eye
• Hydrochloric acid in stomach - acidic pH kills pathogens that are swallowed

Question 23

What is the immune system?

Answer 23

• The body’s defence against pathogens once they have entered the body
• Aims to prevent or minimise disease caused by pathogens

Question 24

How do white blood cells detect pathogens in the body?

Answer 24

Pathogens have unique antigens on their surface which are detected by specialised receptors on white blood cells.

Question 25

How does the immune system destroy pathogens?

Answer 25

• B-lymphocytes (type of WBC) produce antibodies in response to a particular antigen • Each antibody is specific to an antigen and binds to it • Antibodies 'tag' pathogens or clump them together, disabling them so that they can be killed by other WBCs.

Question 26

What are memory lymphocytes?

Answer 26

• WBCs produced in response to a foreign antigen that remain in the body after a pathogen has been destroyed • Provide immunity - if the body is re-infected, antibodies are produced more rapidly and the pathogen is destroyed before it can produce disease symptoms

Question 27

What is a vaccination?

Answer 27

• Deliberate exposure of an individual to foreign antigens • Triggers an immune response (produces antibodies) and provides immunity (due to memory cells) • The individual does not contract the disease that they are being immunised against

Question 28

What are the benefits of vaccinations?

Answer 28

• Herd immunity - vaccination of a significant proportion of the population gives some protection to individuals who are not immune • Helps to prevent epidemics and pandemics

Question 29

What are the drawbacks of vaccinations?

Answer 29

• High mutation rate of viruses changes the structure of viral antigens, making vaccines that are already available ineffective • Not guaranteed to work • Inactivated pathogens may mutate and become pathogenic • May cause an adverse reaction • Vaccination programmes are costly

Question 30

Outline the stages of drug development

Answer 30

1. Screening for potential drugs 2. Preclinical trials 3. Clinical trials 4. Approval by a medical agency

Question 31

Outline the factors that can affect the risk of developing a non-communicable disease

Answer 31

• Lifestyle factors e.g. diet, exercise, alcohol, smoking • Environmental factors e.g. exposure to pollution • Genetics e.g. alleles that increase the risk of cancer

Question 32

What is cardiovascular disease (CVD)?

Answer 32

• Group of diseases affecting the heart or blood vessels • Build up of fatty deposits on the walls of the arteries forms atheromas which reduce blood flow to muscle tissue • Blood clots may form, blocking the arteries and stopping blood flow completely. This can lead to a heart attack or stroke.

Question 33

How can CVD lead to a heart attack?

Answer 33

• Obstruction of a coronary artery (supplies heart muscle) due to an atheroma or blood clot • Results in loss of blood supply to an area of heart muscle • This causes death of the cells and leads to a heart attack

Question 34

How can CVD be treated?

Answer 34

• Improving diet and lifestyle • Medication • Surgery

Question 35

Which medicines are used to treat CVD?

Answer 35

• Statins • Anticoagulants • Antihypertensives