A-LevelBiologyInfectious diseases9700/21 · Oct/Nov 2024 · Q316 Marks

Fig. 3.1 is a photomicrograph of a transverse section through a region of the wall of the bronchus in the gas exchange system. [Figure 3.1]

(a)Identify the tissues J and K shown in Fig. 3.1, and suggest how the wall of a bronchiole differs from the wall of the bronchus for these two tissues.[3]
(b)(i)State the name of the pathogen that causes TB.[1]
(b)(ii)Name the part of the monoclonal antibody that binds to the protein from the pathogen.[1]
(b)(iii)Use the information in Fig. 3.3 to suggest and explain why this test is specific for TB.[2]
(b)(iv)Suggest how the structure of immobilised monoclonal antibodies in area 3 differs from the structure of the immobilised monoclonal antibodies in area 4.[2]
(c)Explain how memory T-lymphocytes provide protection from TB in a person who has been given a BCG vaccination.[3]
(d)(i)Name the process used by the tumour cells to take up the weakened pathogens.[1]
(d)(ii)Suggest how antigen presentation by tumour cells stimulates an immune response that leads to the destruction of the tumour cells.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

3(a) J cartilage;
K smooth muscle ;
difference I ref. to other tissues
plus one from: cartilage in bronchus but not the bronchioles ; suggestion for smooth muscle tissue (ref. to K) ; e.g. proportionally more smooth muscle in the wall of the bronchiole
3(b)(i) Mycobacterium tuberculosis / Mycobacterium bovis ;
3(b)(ii) antigen binding site(s) ; A variable region
3(b)(iii) any two from: A antigen for TB protein A TB pathogen for pathogen causing TB
(immobilised) monoclonal antibody has a binding site which is a complementary shape to the protein secreted by the TB pathogen;
monoclonal antibody on the test line will only bind with protein secreted by the by the TB pathogen;
idea that monoclonal antibodies with tiny gold particle are only held in place if protein secreted by the TB pathogen is present;
AVP; e.g. suggestion that TB protein is specific to the TB pathogen
3(b)(iv) any two from: different shaped, variable region / antigen binding site ;
ref. to different primary structure ;
ref. to a different tertiary structure ;
ref. to different (named) bonds holding the tertiary structure ;
3(c) any three from: provides (long-term) immunity ;
context of pathogen entering the body ref to secondary / fast / strong, immune response ;
because of presence of increased numbers of specific T-lymphocytes ;
memory T-lymphocytes, recognise / bind to / activated by, the foreign antigen ;
T- helper cells secrete. cytokine / interleukins; I cell-signalling molecules
example of consequence of increased cytokine release ; e.g. increased phagocytosis / angry macrophages increased, B-lymphocyte / humoral, response enhance T-killer response
3(d)(i) endocytosis; A phagocytosis
3(d)(ii) any three from: some T-lymphocytes have receptors with a complementary shape to the antigen on the tumour cell ;
antigens on the surface of the tumour cell bind to receptor / ref. to clonal selection;
T-lymphocytes, divide by mitosis / ref. to clonal expansion ;
T-killer cells are produced that destroy the tumour cell;
method used by T-killer cell to destroy tumour cell ; e.g. perforin, hydrogen peroxide, granzymes A toxins
ref. to B lymphocytes and antibodies ;
AVP; e.g. further detail of method used by T-killer cell ref. to phagocytosis of cancer cells