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The diagram below shows the structure of tryptophan - VCE - SSCE Biology - Question 1 - 2023 - Paper 1
Question 1
The diagram below shows the structure of tryptophan. To what group of biological monomers does tryptophan belong? Use information in the diagram to justify your res... show full transcript
Worked Solution & Example Answer:The diagram below shows the structure of tryptophan - VCE - SSCE Biology - Question 1 - 2023 - Paper 1
Step 1
To what group of biological monomers does tryptophan belong? Use information in the diagram to justify your response.
Answer
Tryptophan belongs to the group of biological monomers known as amino acids. This can be inferred from its structure, which includes a central carbon atom bonded to an amino group ( ext{-NH}_2), a carboxyl group ( ext{-COOH}), and a variable R group (indole side chain). These features are characteristic of amino acids.
Step 2
Compare the two mechanisms of regulation.
Answer
In repression, when tryptophan (trp) levels are high, two trp amino acids bind to the repressor. This binding causes a conformational shape change in the repressor, which then enables it to attach to the operator. This inhibits RNA polymerase from binding to the promoter to transcribe the structural genes.
In contrast, attenuation occurs when tryptophan levels are low. Here, RNA polymerase begins transcription of the leader or attenuator sequence, which includes two trp codons. As the ribosome moves along this sequence, if trp levels are still low, a hairpin structure forms in the mRNA that prevents the detachment of both RNA polymerase and the ribosome.
Both mechanisms serve to regulate trp levels, conserving resources in prokaryotic cells.