The bacterium Vibrio cholerae is the causative organism of the infectious disease cholera. V. cholerae has structural features typical of all bacterial cells. It also has a flagellum for movement. (a) Fig. 4.1 is an outline drawing of V. cholerae. Complete Fig. 4.1 by drawing and labelling the structures found in V. cholerae. [Figure 4.1]

Mark scheme

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

1. [4] max 3 if any membrane-bound organelles drawn inside cell e.g. nucleus, Golgi body, mitochondrion, lysosome, ER, a large vacuole
2. BUT I vesicle / small vacuoles
3. I detail of cell wall / cell surface membrane around flagellar area
4. four from:
5. cell wall; must add another line to diagram R cellulose cell wall
6. cell (surface) membrane ; A plasma membrane
7. label line to the inside of cell wall
8. I if outer line labelled as cell membrane
9. DNA; A bacterial chromosome / nucleoid as label
10. allow one or two circular molecules (circle, loop, ball of string, tangled)
11. R if obviously linear
12. R if label includes, histones / histone proteins / chromatin
13. R if nuclear, envelope / membrane, shown
14. R if nucleolus shown or labelled
15. ribosomes; R 80S ribosomes
16. shown as, dots/small spheres
17. cytoplasm / cytosol;
18. plasmid; smaller than DNA, circular
19. AVP; e.g. 70S / smaller / 17–20 nm, for ribosome
20. murein / peptidoglycan (for cell wall – allow even if cell wall label not added)
21. pilus /pili drawn as external hair-like structure(s)
22. basal granule at base of flagellum
23. capsule drawn to outside (some do have a capsule)
24. [1] 0.8%; R 0.80%
25. [2] any two from:
26. delay in /no, diagnosis;
27. delay in /no, treatment / therapy ; A feature of, oral rehydration, treatment /solution A ORT/ORS
28. e.g. lack of supply of ORT
29. unwillingness by health workers to give ORT
30. greater belief in herbal remedies
31. thinking drug treatment is sufficient
32. lack of clean water to make up ORT solution
33. no rehydration programmes
34. I improper treatment / treatment not effective
35. ref. to no / lack of, antibiotic therapy; e.g. lack of supply of/less efficacious (AW) antibiotics used / less supervision in taking full dose
36. ref. to antibiotic resistant strains ;
37. idea that already have a weak immune system / malnourished;
38. A may have HIV/AIDS (hence weak immune system)
39. [1] any one from:
40. damaged sanitation system / poor sanitation following earthquake;
41. I poor sanitation unqualified
42. damage to, sewage treatment plants / water purification plants; AW
43. (contaminated) sewage contaminates drinking water ; I pollution
44. A water becomes contaminated
45. lack of purified drinking water; A lack of, clean / treated / safe / bottled, water
46. AVP; no, proper / safe, disposal of sewage
47. [3] any three from:
48. 1 2011, peak in / highest / AW, number of, cases / countries / countries and cases ; A decrease, increase in 2011, decrease for countries A increase to 2011 and decrease for cases
49. 2 (2010 outbreak in) ref. to Haiti and epidemic (so high number of 2011 cases);
50. 3 ref. to spread of disease to countries neighbouring Haiti (hence increase in countries in 2011);
51. 4 overall / generally / AW, decrease in number of countries with cases of cholera or 2008 54-56 countries and 2015 41–43 countries, with ref. to decrease ; decrease, peak at 2011/increase in 2011, decrease is mp1 only
52. 5 suggestion for trend in decrease in number of countries ; e.g. improved infrastructure for sewage / water treatment improved health education to prevent spread providing piped (treated) water
53. 6 2008-2010 number of cases increased and number of countries decreased ;
54. 7 AVP; e.g. lowest / AW, number of cases in 2013 R if also state that 2013 is lowest for countries
55. similar number of countries in 2008 and 2011 but, approx 3x / much higher / stated values, number of cases in 2011