Describe how a virus differs from a bacterium.

Mark scheme

Marking points from the official mark scheme (May/June 2014). The mark or mark type is shown in brackets.

1. [6] Viruses
2. DNA or RNA both must be noted for mark and as possibilities;
3. parasitic/disease causing AW/reproduce only in host cell ;
4. A harmful/active only in host cell
5. Bacteria
6. contain DNA ;
7. saprotrophic/decomposers AW ;
8. ref. binary fission/asexual reproduction/mitosis ;
9. Comparative points
10. protein coat/no protein coat ;
11. not truly living/living;
12. no (cell) wall /(cell) wall ;
13. no spores/forms spores ;
14. no cytoplasm*/cytoplasm ;
15. *A no ribosomes/protoplasm/flagella/plasmid/cell membrane ORA R nucleus/mitochondria
16. not affected by/affected by antibiotics;
17. size comparison ;
18. viruses less than 300 nm – bacteria c. x 50 larger
19. A viruses small(er) than bacteria
20. Accept points on labelled diagrams
21. Ig loop/strand/RNA
22. R protein wall
23. A acellular
24. Ig composition of the wall
25. [4] decomposition/decay/putrefaction;
26. saprotrophic;
27. A saprophytic
28. release enzymes/ref. external digestion ;
29. A named enzyme
30. insoluble to soluble;
31. example of macromolecule and breakdown product, e.g. protein to amino acids ;
32. respiration;
33. CO2 released + photosynthesis ;
34. water released + later use ;
35. nitrification;
36. NH4+/NO2/NO32- ;
37. R ammonia/NH3
38. salts for plant uptake ;