Biology 9700 · AS & A Level · Protein synthesis

Protein synthesis — practice question

Fig. 4.1 depicts the primary structure of a lysozyme molecule, an enzyme present in tears, saliva and lysosomes.
(a(i))[1]

Explain what the term primary structure means.

(a(ii))[3]

The molecular structure of the first two amino acids in lysozyme, lysine and valine, is shown. Use the space provided to show how these amino acids are joined in a condensation reaction.

(b(i))[5]

Describe the secondary and tertiary structure of an enzymatic protein, for example lysozyme. secondary … tertiary …

(b(ii))[1]

State why enzymes, such as lysozyme, need a tertiary structure.

(c)[3]

A rare disease is caused by a single change in the DNA nucleotide sequence of the gene that codes for lysozyme. This change produces an insoluble protein with a different structure from the normal soluble lysozyme molecule. Suggest how a change in the gene can explain the differences observed between the normal lysozyme and the altered lysozyme.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Primary structure is the amino-acid sequence, or order/arrangement, within a polypeptide chain.

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