Cell recognition and Immunity practise questions

Question 1

Explain why antibodies are only effective against a specific pathogen (2 marks)

Answer 1

• Antigens on the pathogen are a specific shape/Have a specific tertiary structure
• Antigen-antibody complex forms

Question 2

Describe the process of phagocytosis (4 marks but 6 possible points)

Answer 2

• Phagocyte attracted by a substance/ recognised foreign antigen
• Pathogen engulfed
• Enclosed in a vesicle/Phagosome
• Phagosome fuses with lysosome
• Lysosome contains hydrolytic enzymes
• Pathogen digested/hydrolysed

Question 3

Scientists use an antibody to detect an antigen on teh bacterium that cuases stomach ulcers.
Explain why the antibody will only detect this antigen? (3 Marks)

Answer 3

• Antibody/Variable region has specific amino acid sequence/primary structure
• The shape/ tertiary structure on the binding iste is complementary to the antigen
• Antigen-Antibody complex forms

Question 4

Antigens are proteins. Explain why a knowledge of antigens can show that animals are genetically similar

Answer 4

• Protein/Antigen production is determined by alleles/genes on DNA
• The more similar the proteins the more similar the alleles/more genetically similar

Question 5

Give one reason why you should have straight lines plotted from point to point in data

Answer 5

Because it is impossible to predict values between points

Question 6

Give two reasons why an increase in antibody production in mice will not neccesarily mean humans can have resistence to disease

Answer 6

• They only tested on mice-not represnetive of humans
• Not all diseases cured by antibodies