Biology HL
Protein Folding and Function
- 1.
A linear polypeptide contains 120 amino-acid residues. Calculate the number of peptide bonds formed during its assembly, name the two types of functional group joined, and explain why changing one residue can alter function without changing chain length.
[4 marks] · no calculator - 2.
A soluble globular protein has many non-polar R-groups buried inside and charged R-groups exposed to water. Explain this arrangement, identify two other interactions stabilizing tertiary structure, and explain how a major pH change may disrupt the fold without necessarily hydrolysing its peptide backbone.
[4 marks] · no calculator - 3.
Insulin is a compact protein hormone, whereas collagen forms long fibres that resist tension. Explain how the different forms suit signalling in blood and mechanical support, and distinguish tertiary from quaternary structure in a protein containing multiple polypeptide chains.
[4 marks] · no calculator - 4.
A hypothetical globular enzyme loses activity when heated, but analysis shows its amino-acid sequence is unchanged. Explain how activity can be lost without peptide-bond hydrolysis, and why cooling does not guarantee restoration of activity.
[3 marks] · no calculator - 5.
Compare soluble insulin with collagen as examples of proteins whose shapes suit different roles. Explain why both can contain peptide bonds even though one acts as a signal and the other provides tensile strength.
[3 marks] · no calculator