Biology 9700 · AS & A Level · Protein synthesis

Protein synthesis — practice question

(a)[1]

Enzymes consist of polymers made from amino acids. Complete Fig. 3.1 so that it shows the general structure of an amino acid.

(b(i))[1]

Calculate the rate of reaction when the standard brown colour was reached after 2 minutes 30 seconds. The rate of reaction, $R$, was found using the formula $R = \frac{1}{\text{time to reach standard brown colour in minutes}}$.

(b(ii))[1]

Fig. 3.3 presents a graph of the investigation results. State how the data in Fig. 3.3 show that substrate was in excess at every concentration of catechol oxidase tested.

(c(i))[3]

Explain the form of the curve shown in Fig. 3.4.

(c(ii))[1]

Use Fig. 3.4 to calculate the Michaelis-Menten constant ($K_m$) for the reaction involving catechol oxidase and catechol.

(c(iii))[1]

Methylcatechol is similar in shape to catechol. Catechol oxidase can also act on methylcatechol as a substrate. Under identical conditions, the $K_m$ value for the reaction with methylcatechol as the substrate was much lower than the $K_m$ value for the reaction with catechol as the substrate. State what these $K_m$ values reveal about the relationship between the enzyme and the two substrates.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: The amino acid structure has all four atoms and the $ R$ group correct.

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