Baculovirus is a virus that kills some of the insect pests of major crops. When the virus is released to the outside of the insect body, it is contained within stable, protective structures known as polyhedrons. The main component of the polyhedron is a protein molecule, polyhedrin. Polyhedrons can be sprayed onto plants as a bioinsecticide. They are ingested by feeding insect larvae and once inside the insect gut they break down to release the virus.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

1. [2] any two from:
2. infectious
3. (baculovirus) is a pathogen / causative organism (of disease) ;
4. (baculovirus) is transmitted (from one insect host to another) / transmissible ;
5. allow a description of transmission, e.g. transfer of, virus / pathogen, from, insect to insect/ organism to organism I spread R person to person / plant to plant
6. disease
7. idea of causing ill-effect on insect, e.g. causes, harm / damage / loss of functioning / ill health / death ; A illness
8. [2] any two from:
9. (highly) alkaline / acidic (conditions) ; A (very) low / high, pH
10. disruption of, hydrogen / ionic, bonds, of (polyhedron) proteins / polyhedrins ;
11. (presence of) digestive enzymes / hydrolytic enzymes / hydrolases ;
12. R if stated as within lysosomes but allow detail of enzyme action ecf
13. detail ; e.g. extracellular enzymes / proteases / peptidases
14. peptide bonds broken A amide bond for peptide bond
15. optimum pH ; must be in context of enzyme presence
16. [4] if detail is linked to incorrect level of structure or levels of structure not named, max 3
17. 1 primary structure detail ; e.g. sequence of amino acids / ref. to sequence in Fig 3.1 (many) amino acids joined by peptide bonds
18. 2 secondary structure detail ; e.g. has, a / alpha, helices has ẞ / beta, pleated sheets A ẞ / beta, pleats has areas of random coils / AW
19. 3 tertiary structure detail ; e.g. interactions between, side chains / R groups (R group interactions are) H bonds, ionic bonds, hydrophobic interactions, disulfide bridges any two folding and coiling in context of polypeptide chain
20. 4 quaternary structure detail ; e.g. three (identical) polypeptide chains ref. to interaction of polypeptide chains A polypeptides for polypeptide chains
21. [3] any three from:
22. ref. to genetic code ; in correct context
23. amino acids coded for by more than one codon / two or more codons for (most) amino acids ;
24. A triplet (of, bases / nucleotides)
25. 64 codons and 20 amino acids ;
26. third base in codon can be different / only first two bases in codon are same ;
27. AVP ; idea that amino acid sequence is only the result of exons / gives information only about introns
28. only sure of sequence for, two amino acids / met and trp
29. degenerate code / degeneracy of code R degenerative
30. ref. to control sequences
31. STOP codons (also) have more than one triplet (of bases)
32. STOP codons do not specify amino acids