Countries that have a high number of cases of malaria also have problems with diseases caused by bacteria. This means that many people in these countries are prescribed antibiotics, such as penicillin, for the treatment of bacterial infections. The female Anopheles mosquito is the vector of the Plasmodium pathogen that causes malaria. The insect takes in Plasmodium when feeding on blood from an infected person. At a later stage the insect can transmit the pathogen when taking a blood meal from an uninfected person. [Figure 5.1]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

1. [3] (a) 1 prevents formation of, cross links / cross linkages (between, peptidoglycan / murein, chains); A peptide cross links A links between, murein / polymer, chains I peptide bonds I formation of peptidoglycan R if cellulose chains stated 2 (penicillin) inhibits, transpeptidase action / enzyme involved in forming cross links; A alternative correct names for transpeptidase 3 weakens cell wall ; A cell wall unable to withstand (turgor) pressure A cell wall loses strength R idea that penicillin, punches / makes, holes, to weaken 4 (cell), lysis / bursts / ruptures / AW (so bacterium killed) ; 5 acts, on growing bacteria / when bacteria are increasing in size (when cell wall needs to be synthesised); I growing, wall / peptidoglycan chains
2. [1] (b) (Plasmodium / P.), ovale / falciparum / malariae / vivax ; correct spelling I if Plasmodium is written after the species name if more than one given, all must be correct
3. [1] (c) any one valid suggestion: male does not, need protein for egg production / produce eggs ; R larvae I male does not reproduce male does not have mouthparts for piercing skin; AW e.g. no 'needle' to pierce skin (to suck blood) adult male does not feed; adult male feeds (only) on, plants / nectar ; blood is toxic to males; can't detect presence of, humans / mammals; male does not produce anticoagulant (for blood);
4. [3] (d) accept mosquito or vector for Anopheles accept, pathogen / parasite, for Plasmodium max 2 1 idea that individuals / people, taking antibiotics for bacterial diseases will pass on antibiotics to Anopheles when it feeds; e.g. blood taken by Anopheles contains antibiotics 2 (so) antibiotics kill bacteria (in Anopheles gut); must be in context of gut bacteria 3 decreased / no, competition between, Plasmodium and (gut) bacteria (so more Plasmodium survives) ; 4 higher survival of Plasmodium makes effective (Anopheles) immune response more difficult ; AW (so Anopheles more likely to pass on Plasmodium) max 2 I ref. to antibiotic resistance 5 use of antibiotics may increase, incidence / number of cases of, malaria ; 6 and 7 two marks for examples of what doctors need to consider ; e.g. need to balance antibiotic intake with increased risk of malaria transmission idea that do not want to stop people taking antibiotics / antibiotics needed to fight (bacterial) infections treat for malaria before giving antibiotics for (non-serious / non-life threatening) bacterial infections only prescribe antibiotics that have, no / low, impact on bacteria in Anopheles (gut) (consider) avoiding use of antibiotics to treat malaria 8 AVP; e.g. need to research which antibiotics have this effect look for alternatives to antibiotics to treat bacterial infections
5. [4] (e) any four from: 1 (Plasmodium) is a, eukaryote / protoctist, so has many antigens ; R bacterium / virus, is a eukaryote or (Plasmodium) has many genes coding for (different) antigens ; I antigenic variation 2 idea that different Plasmodium species have different antigens; I antigenic variation I strains for species 3 (Plasmodium) has different stages of life cycle (within human) with different antigens / shows antigenic variation ; 4 antigenic concealment / Plasmodium spends part of life cycle within host cells / AW; A short time in blood plasma A spends time inside, red blood cells / liver cells 5 need to find the antigens that give the strongest immune response ; 6 need to, develop / use, more than one type of vaccine ; A cannot use only one type of vaccine 7 AVP; e.g. mutations will give changed antigens need to find antigens present in, all / most, stages of life cycle difficulties in producing a generic vaccine max 2 8 costly to produce / need to keep costs low / developing countries need to be able to afford vaccine ; 9 needs to have a long shelf life / be stable / be easily stored (e.g. without cold storage) / AW ; 10 (immunity) needs to be long-lasting / aim to avoid boosters / need to develop a single dose vaccine; AW