Around $2 \times 10^9$ people worldwide are presently infected with the bacterial disease tuberculosis (TB), which is caused by Mycobacterium tuberculosis. Early diagnosis matters because treatment can then start without delay.
APOPO is a non-profit organisation that has trained African giant pouched rats, Cricetomys gambianus, to use their sense of smell to find M. tuberculosis. They do this by sniffing a sample of thick mucus from the lungs of people who may have TB. The African giant pouched rats can detect the presence of M. tuberculosis with an accuracy of 87-93%.
Fig. 8.1 shows an African giant pouched rat.
(a(i))[1]
The receptor cell type used by African giant pouched rats to detect M. tuberculosis is the same type found in human taste buds.
Name this receptor cell type.
(a(ii))[2]
Suggest why African giant pouched rats trained to detect M. tuberculosis may also be able to detect other species of Mycobacterium that cause TB.
(b)[2]
Fill in Table 8.1 to give the complete classification of the African giant pouched rat.
(c)[4]
Differences between organisms in domain Eukarya and organisms in domain Bacteria include whether certain membrane-bound cell structures are present. Outline other differences in the characteristic features of members of the domain Eukarya and members of the domain Bacteria.
(d)[2]
Describe, with reference to viral structure, how viruses are classified.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correctly identifies a chemoreceptor” …