(a)[2]
Outline the meanings of primary structure and tertiary structure in a protein.
(b(i))[2]
Illustrate, with a diagram, the way disulfide cross-links are formed.
(b(ii))[1]
What type of reaction is shown?
(b(iii))[4]
State three further interactions that stabilise protein tertiary structure.
(c(i))[1]
What type of bonding stabilises the $\beta$-pleated sheet in silk?
(c(ii))[3]
On the diagram below, add a second polypeptide strand and show how the bonds that stabilise this $\beta$-pleated sheet would form.
(d)[1]
Suggest why the $\beta$-pleated sheet in $\beta$-keratin is much less flexible than the $\beta$-pleated sheet in silk.
(iii)[4]
State three further interactions that stabilise protein tertiary structure.