Biology 9700 · AS & A Level · Protein synthesis

Protein synthesis — practice question

Fig. 2.1 shows a transmission electron micrograph of part of a specialised epithelial cell in the stomach lining. This cell makes extracellular proteins that are then released into the bloodstream.
(a)[2]

Outline how structure X and structure Y, shown in Fig. 2.1, are involved in making extracellular proteins. structure X structure Y

(b(i))[1]

State the level of protein structure that is shown in Fig. 2.2.

(b(ii))[1]

State one similarity between the structure of a saturated fatty acid molecule and an amino acid molecule.

(b(iii))[3]

The attachment of the fatty acid chain enables ghrelin to act as a cell signalling molecule. Suggest how the attachment of this fatty acid chain enables a ghrelin molecule to act as a cell signalling molecule.

(c(i))[2]

Scientists have found that the gene coding for ghrelin has 5000 base pairs. This is a much larger number of base pairs than are required to code for the ghrelin molecule shown in Fig. 2.2. Calculate the percentage of base pairs in the gene that code for the ghrelin molecule shown in Fig. 2.2. Show your working and give your answer to one decimal place.

(c(ii))[2]

The primary transcript made from the ghrelin gene is a longer molecule than the mRNA present in the cytoplasm. Explain how the primary transcript is modified before translation.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: $X$: nucleolus makes ribosomal subunits / ribosomes

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