A-LevelBiologyImmunity9700/22 · Feb/Mar 2023 · Q411 Marks

Tuberculosis (TB), influenza and polio are examples of infectious diseases.

(a)(i)Explain what is meant by an infectious disease.[2]
(a)(ii)Name a species of organism that causes TB.[1]
(b)Immunity can be described as artificial or natural and passive or active. Name the type of immunity that a mother gives to her baby through breast milk.[1]
(c)The influenza virus can mutate frequently to produce different strains of the virus. A new vaccine is often necessary to stimulate the production of new antibodies to these new strains. Explain why different antibodies need to be produced to give immunity to these new strains.[3]
(d)(i)Polio is a serious viral disease affecting young children. In 1996, polio caused paralysis in more than 75000 children across Africa. A long-term vaccination programme allowed the World Health Organization (WHO) to declare that Africa was largely free of polio in 2020. Explain how vaccination programmes can help to control the spread of infectious diseases, such as polio.[3]
(d)(ii)Antibiotics, such as penicillin, do not help to prevent the spread of viral diseases, such as polio. Explain why penicillin is not effective against viruses.[1]

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2023). The mark or mark type is shown in brackets.

[2] Question 4(a)(i) Answer caused by pathogens ; is transmissible / AW ;
[1] Question 4(a)(ii) Answer Mycobacterium tuberculosis / Mycobacterium bovis ;
[1] Question 4(b) Answer natural and passive ;
[3] Question 4(c) Answer any three from: 1 (as influenza virus mutates) antigen (proteins) altered / altered capsid proteins / AW ; 2 antibodies are specific to antigens ; 3 ref. to complementary shape (between variable regions of antibody and antigen) ; 4 ref. to variable regions / Fab, at the ends;
[3] Question 4(d)(i) Answer for children, allow people for polio allow disease any three from: 1 ref. to vaccination programme aims to vaccinate, whole populations / large numbers ; 2 vaccine allows (most), children / people, to have an immune response (against antigens of the disease organism) ; 3 develop, long-term immunity / artificial active immunity / memory cells against, polio / disease ; 4 idea that vaccinated individuals cannot, transmit virus / transmit polio / infect others; 5 herd immunity / described ; 6 AVP; e.g. ref. to vaccination programme aims to break the transmission cycle
[1] Question 4(d)(ii) Answer any one from: penicillin only acts on, bacteria / prokaryotes ; virus does not have, cell walls / murein / peptidoglycan; virus does not have, transpeptidases / the enzyme that is, inhibited / acted on, by penicillin ; virus does not grow / penicillin (only) acts on growing cells / AW ; A when cell wall is, growing (larger) for growing cells virus does not have cellular structure / virus is acellular ;