Health And Disease

Question 1

Describe how the malarial parasite is transmitted

Answer 1

FEMALE ANOPHELES MOSQUITO
Takes blood meal from infected person
Takes blood meal from uninfected person
Parasite transferred in mosquito’s saliva

Question 2

Explain how vaccines provide long term immunity to diseases

Answer 2

Protein in vaccine = antigen
Following vaccination: clonal selection for appropriate B cell
Clonal expansion/ divide by mitosis to form B cell clone
Memory cells
on infection by parasite
B cells secrete antibody
Secondary response/ rapid production of antibody
Antigen-antibody specificity
Antibody attaches to surface protein on parasite
Prevents attachment to red blood cell

Question 3

Explain why it’s so difficult to develop a vaccine to malaria

Answer 3

Genetic complexity of Plasmodium
Many genes
Many antigens
Many stages in life cycle within human
Antigens change/ antigenic variation
plasmodium lives within cells

Question 4

Drug is used to inhibit enzyme.how might this drug act on an enzyme to prevent it from functioning

Answer 4

Drug is competitive inhibitor or non-competitive inhibitor

Competitive: drug molecule has same surface protein as substrate/ same shape as substrate
Drug molecule fits into active site
Blocks access to active site/ prevents formation of ES complex

Non-competitive inhibitor
Drug molecule fits into allosteric site
Active site changes shape so cannot accept substrate
Permanent/ irreversible

Question 5

Describe the mode of action of a macrophage against a bacterial cell

Answer 5

Detection of bacterium/ foreign antigens
Macrophage has receptors for antigen
Engulfs bacterium
Forms phagosome (/vesicle/ vacuole)
Lysosome fusion 
Hydrolytic enzymes 
Antigen presentation

Question 6

Suggest one way in which a bacterial cell may survive within a macrophage

Answer 6

Bacterial cell produces inhibitors for the hydrolytic enzymes
Escapes out of phagosome
Is resistant to digestive enzymes

Question 7

Describe the defence mechanisms other than immune cells which humans have to protect against bacteria

Answer 7

Production of mucus by mucous glands/ goblet cells
Sticky mucus traps bacteria
Mucus acts as a barrier to prevent entry
Mucus increases distance to reach cells
Cilia on ciliated epithelial cells
Cilia waft mucus
Idea that mucus is moved away from alveoli

Question 8

Suggest how bacteria may spread from the lungs to other tissues

Answer 8

Through the blood
Through the lymph system
Within neutrophils/ macrophages

Question 9

How is TB spread

Answer 9

Eating contaminated beef
Eating beef from infected cattle

Drinking unpasteurised milk from infected cows
Drinking contaminated milk

Question 10

Explain how binding to RNA polymerase allows rifampicin to kill mycobacterial cells

Answer 10

Rifampicin binds to RNA polymerase so mRNA is not synthesised so polypeptides not synthesised

OR prevents elongation of mRNA so polypeptides not synthesised

Question 11

Outline three economic factors that need to be considered in the prevention and control of multi drug resistant (MDR) TB

Answer 11

Education about ways to prevent spread
Less cramped accommodation
More effective treatments against the diseases
Cost of a Vaccination programme means less money available to health authorities
Cost of longer drug treatment means less money available to health authorities
Research into new drugs