Describe the relationship between genes, polypeptides and enzymes.

Outline control of metabolic pathways.

gene is a sequence of DNA bases;
DNA/gene codes for a specific sequence of amino acids/polypeptide;
enzymes are proteins/composed of polypetides;
sequence of amino acids determines tertiary structure/folding/shape of active site;
change in the gene/mutation will affect the active site/function of an enzyme;
enzymes are involved in replication/transcription of genes;
enzymes are involved in synthesis of polypeptides;

metabolic pathways can be a sequence/chain of reactions;
they can be cycles of reactions;
different enzymes control each reaction in the sequence/cycle;
accumulation of an end-product can inhibit the first enzyme of the sequence/ pathway;
(an end-product inhibitor) joins an allosteric site/a site separate from active site;
attachment at the allosteric site changes the shape of the active site;
preventing the binding of substrate;
until the level of the end-product is reduced (and the inhibition removed);
this is an example of negative feedback;

This part of the question was poorly answered. Candidates were usually able to relate genes to translation but were less likely to adequately relate their responses specifically to polypeptides beyond that.

Aspects of allosteric inhibition were usually a strength within student responses to this question. Answers for this question were generally not very well constructed.